Antioxidants In Food

By Beatrice Trum Hunter
Food For Thought Column
Consumers' Research Magazine
1999

Antioxidants, naturally present in many foods, appear to benefit health overall. They are credited with preventing cell damage linked to the development of degenerative conditions such as coronary artery disease; atherosclerosis; cataracts; Alzheimer's, Lou Gehrig's, and Parkinson's diseases; and cancers. Antioxidants may promote immune system function, especially in elderly individuals, and retard the aging process. Antioxidants may reduce the susceptibility of undesirable low density lipoprotein (LDL) cholesterol to oxidation,which leads to plaque formation in the arteries. Antioxidants help prevent damage to the DNA in sperm, and thus prevent birth defects and childhood cancers.

These favorable features of antioxidants have led to consumer interest in finding ways to increase dietary levels of them, and for food processors to fortify foods with them.

Dietary antioxidants differ one from another, and their functions differ under various circumstances. They are not interchangeable because their mechanisms differ. As illustration, beta carotene, an antioxidant in carrots, does not act the same way as vitamin C, an antioxidant in oranges. However, some antioxidants work in tandem. Examples are vitamin E and selenium. Different antioxidants affect different sites. For instance, beta carotene protects against lung cancer; and vitamin C, against stomach cancer.

Antioxidants combat the harmful effects of oxidation in the body, by blocking the free radical chain reactions that result in cell damage. Free radicals result from normal metabolic processes in which oxygen molecules lose electrons. This creates unstable molecules (the free radicals) that cause oxidative stress. The free radicals attack the body's healthy cells by attempting to find other electrons to stabilize them. This process causes damage to healthy cells unless they are protected by antioxidants.

Currently, Recommended Dietary Allowances have been established for only three antioxidants: vitamins C and E, and selenium. A recent report by the Panel of Dietary Antioxidants and Related Compounds, released jointly by The Institute of Medicine (IOM) and the National Academy of Sciences (NAS), reviewed food components that demonstrate antioxidant effects, in order to establish levels for Dietary Reference Intake (DRI). Vitamin C and E, and selenium are being considered, and carotenoids have been added. These are considered "The Big Four."

Vitamin C scavenges reactive oxygen and nitrogen species (both free radicals) and is very powerful in attacking substances that cause inflammation. Also, vitamin C helps in reacting with other antioxidants such as vitamin E and selenium, and regenerates them back into their natural antioxidant forms.

Vitamin E may delay Alzheimer's disease, and protect against cancer. In diabetes, the increased oxidative stress may be related to a person's underlying metabolic abnormalities, and be relieved by the antioxidant quality of vitamin E.

Selenium increases the protective effects of vitamin E. Among its antioxidant effects, it may protect against advanced prostate cancer.

Beta carotene, from a family of carotenoids, acts as a scavenger against free radicals, and quenches singlet oxygen (a free radical).

Numerous other antioxidants exist in basic foods. Among them are lutein and zeaxanthin. Their molecular structure is similar to beta carotene. At high concentrations, zeaxanthin is an oxygen quencher. Both lutein and zeaxanthin are found in high concentrations in the lens and retina of the eye, as well as in the liver and kidney. An abundant intake of foods containing these two antioxidants has been associated with lower levels of eye disease and lung cancer.

Lycopenes, common in tomatoes, are the most efficient carotenoid quenchers of singlet oxygen. Polyphenols, found in most fruits and vegetables, show antioxidant behavior in tests. Lipoic acid, essential for energy metabolism, permeates cells readily, and may be an antioxidant. Combined with vitamin E, it enhances the antioxidant effect. Lipoic acid is present in spinach and in meat.

Natural antioxidants have been identified in a variety of foods, including many fruits and vegetables; grains; garlic; honey; tea leaves; and coffee and cocoa beans. Also, they have been identified in many plants, such as burdock root, milk thistle, and ginkgo (Ginkgo biloba).

Herbs and spices contain antioxidants. Many food processors now substitute essential oils from rosemary, oregano, and thyme for the formerly used synthetic antioxidants, to keep fat-containing foods from turning rancid. These substances have antimicrobial as well as antioxidant qualities, which may account for their effectiveness in preserving perishable meats in past centuries. Currently, some food processors use vitamin C and E to help keep meats fresh.

The report from the IOM/NAS panel proposed a definition for dietary antioxidants, in order to characterize the properties of these compounds. The panel decided on three criteria: an antioxidant must be found in the human diet; data on the food component must exist in measurable quantities in reliable food consumption databases; and the substance must demonstrate that it decreases the adverse events of free radicals in humans.

Much information is still lacking in identifying naturally occurring antioxidants in foods and their functions. This work will continue to evolve, and reinforce the truth that basic foods offer health benefits, not only from nutrients, but also from other constituents that we have only begun to acknowledge and investigate.

YOU ASKED FOR IT: QUESTIONS AND ANSWERS

Q. What fruits and vegetables show the most antioxidant activity?

A. Antioxidant activity is measured in Oxygen Radical Absorbance Capacity (ORAC) in test tube experiments. ORAC is a measurement of the ability of foods to subdue oxygen free radicals. Combinations of nutrients in foods have greater protective than single ones.

The highest ORAC in fruits (in descending order) are prunes, raisins, blueberries, blackberries, strawberries, and raspberries. Lower ORAC levels, but still beneficial are in plums, oranges, red grapes, and cherries. For vegetables, kale and spinach top the list, followed, in descending order, by Brussels sprouts, alfalfa sprouts, broccoli florets, beets, red bell peppers, onions, corn, and eggplant.

The author, Beatrice Trum Hunter, MA, has written more than 30 books on food and environmental issues, frequently before widespread public awareness. She was food editor of Consumer's Research Magazine for more than two decades. She is an honorary member of The Price Pottenger Nutrition Foundation, as well as an honorary fellow of The International Academy of Preventative Medicine and an honorary member of The American Academy of Environmental Medicine. She has been the recipient of many awards, including The Jonathan Forman Award of The Society for Clinical Ecology, The New Hampshire Society for Preventative Dentistry, and The Donnon Pepper Humanitarian Award. She can be reached at 243 Falls Road, Deering, N.H. 03244

CHAGA MUSHROOM ( above) has been found to have one of the highest ORAC values  and can be bought in bulk at Mountain Rose Herbs Below. I make a tea out of Chaga mushroom but I like to call it a coffee because with milk and honey it is a close match. Chaga has a flavor somewhat reminiscent of vanilla. I think its delicious. The same pieces of chaga can be reused  several times. It has many health benefits. Check it out under Bulk Herbs and Spices. If you live in North America...in the northern regions, you may want to forage for it. It grows on birch trees. I found some in the wild in Vermont and was very excited about that.

LEPTIN: A FAT REGULATOR IN THE BODY

A Fat Regulator In The Body
By Beatrice Trum Hunter
Consumers' Research Magazine 7/99

Leptin, a hormone made by the body's fat cells, is thought to play a role in regulating body fat by acting as an appetite suppressor. Leptin was discovered only as recently as 1994. Researchers are trying to understand its underlying mechanisms. Apparently, leptin not only regulates fat, but seems to have additional roles as well.

When leptin functions properly, it signals the body to stop eating by producing a feeling of fullness. High leptin levels in obese individuals may reflect malfunctioning of leptin.

People with high leptin levels in the blood are more likely to have insulin resistance than those with lower levels.. Insulin resistance is a condition in which cells do not respond effectively to insulin's message to take up sugar from the bloodstream. People with insulin resistance are at greater risk of developing diabetes, high blood pressure, and low levels of beneficial high-density lipoprotein (HDL) cholesterol. These conditions can contribute to heart disease development.

Cholesterol is a poor predictor of heart disease. Some people with normal - range blood cholesterol nevertheless have heart attacks. Measuring blood leptin levels might be a better marker for the potential risk of heart disease in people who show none of the traditional signs associated with this condition, including high blood cholesterol.

Leptin may play a role in diseases associated with a fat abdomen, a feature common in aging. A person with an "apple" shaped body, with fat deposited mainly around the waist rather than on the thighs or hips, is at greater risk of insulin resistance and heart disease.

In rat studies, leptin enhanced insulin's effects significantly. Moderately obese animals, given an infusion of leptin for eight days, ate less and lost weight. The fat loss from their abdomens was greater than from other body parts.

Leptin may regulate weight in young children. Lactating women have lower concentrations of leptin in their milk than in their blood. The breast may not make or concentrate leptin, but passes leptin to the nursing infant from the mother's blood, indirectly through the milk. This finding suggests that the leptin delivered in breast milk may lead to some mechanism that regulates the child's weight later in life. If this is confirmed, it adds yet another benefit, among many, offered by breast milk but not available from feeding formulas.

In experiments with mice, injected leptin helped obese animals lose weight. Could this have similar effects in overweight humans? Leptin passes safety tests, and was injected into 70 obese adult volunteers in the Program of Obesity and Metabolism at Tufts University. All participants were on individually tailored weight- reduction diets that provided 500 kilocalories less than each person's basic daily energy needs. By the end of the first month, all participants lost weight. The amounts lost were proportionate to their leptin intake levels. Those injected with the highest leptin amounts lost an average of nearly 16 pounds each over 6 months. Some participants lost weight at all dose levels, but the amount lost was highly variable.

Leptin may play a role in adult onset type diabetes and in heart disease. A study of 74 healthy men showed that those with the highest leptin concentration in blood were at high risk of suffering from insulin resistance.

Leptin may play an immunologic role. A group of immune cells, known as helper T cells, have leptin receptors (surface proteins that allow a cell to respond to leptin). Leptin encourages helper T cells to secrete certain chemicals that guide the actions of the immune system. For example, they help ward off viruses, bacteria, and fungi. This finding may explain why malnourished people are so vulnerable to many infectious diseases. Malnourishment leads to extensive metabolic and hormonal changes in the body.

Currently, researchers are investigating leptin to learn whether it can prevent malnourished mice from suffering increased rates of infection. If results are positive, leptin could serve as an immune system booster for low birth weight babies who often experience a wasting syndrome.

By leptin's signaling malnutrition or starvation, the body knows when to shut down energy-expensive functions. For example, women with little body fat, such as marathon runners or ballet dancers, often stop menstruating. The body may have interpreted a leptin lack as a signal to avoid reproduction. Falling leptin concentrations in the blood may instruct the body to suspend temporarily the actions of the immune system.

Leptin has been found to play another role, in helping to maintain a balance between the blood supply and the fat tissue mass. Leptin may stimulate the growth of new blood vessels needed when fat increases in volume. Also leptin may spur the growth of endothelial cells that form blood vessels in the maturing egg and early embryo. Also it may spur wound healing. Leptin may be deployed by some cancer cells to recruit blood vessels. If any tumors are found to make leptin, this finding might serve as a useful tool to control tumor growth.

Commonly used weight-control measures such as diet and exercise, as well as drugs, may produce short-term success but not sustained weight loss. For most people, according to Gerald Bernstein, M.D., president of the American Diabetes Association, "weight loss is an ordeal that requires a truly punitive lifestyle that includes a remarkable reduction in calories." The discovery of leptin as fat regulator, as well as its other roles in the body, contributes fresh insights for long recognized problems.

The author, Beatrice Trum Hunter, MA, has written more than 30 books on food and environmental issues, frequently before widespread public awareness. She was food editor of Consumer's Research Magazine for more than two decades. She is an honorary member of The Price Pottenger Nutrition Foundation, as well as an honorary fellow of The International Academy of Preventative Medicine and an honorary member of The American Academy of Environmental Medicine. She has been the recipient of many awards, including The Jonathan Forman Award of The Society for Clinical Ecology, The New Hampshire Society for Preventative Dentistry, and The Donnon Pepper Humanitarian Award. She can be reached at 243 Falls Road, Deering, N.H. 03244

Plastic Packaging Contaminating Our Foods

Some Unanticipated Interactions
By Beatrice Trum Hunter
Republished with permission from Author
Taken from the Dec. 1993 issue of Consumers' Research Magazine

More than a decade ago, it was discovered that an ordinary Styrofoam cup could disintegrate when it held hot tea and lemon. Discoveries of such unanticipated interactions still occur from time to time.

For many years polystyrene egg containers have largely replaced paper mache. However, their safety has only recently been investigated, in 1991. The Louisiana Agricultural Experiment Station reported that volatile styrene monomers were detected in shell eggs stored in polystyrene containers for two weeks in the supermarket.  Egg dishes cooked with these contaminated eggs contained seven times more ethylbenzene and styrene than those prepared from fresh farm eggs that had not been packaged in polystyrene. It is suspected that the volatile compounds can migrate through the porous shells into the edible portions of the eggs.

Benzene from multilayer, oxygen-barrier, laminated bags has been found to migrate into meat, poultry, cheeses, and other packaged foods. This problem surfaced in September 1990 when an off odor was noticed in a roast beef shipment. Investigation showed the meat contained benzene from the packaging, ranging from less than 5 parts per billion(ppb) to 17.8 ppb in raw meat. The benzene volatilized when the meat was heated.

Increasingly, plastic food wraps and containers have gained in popularity for microwaving foods. This practice can release components from the plastics, including base monomers, plasticizers, colorants, and stabilizers,especially when high heat is used. Many plastics contain plasticizers, used to increase the wrap's flexibility. Some plasticizers have been found to migrate from the plastic into the food. One is DEHA [di(ethylhexyl) adepate], commonly used as a plasticizer in polyvinyl chloride (PVC) film wrap, which is popular for covering stored and microwaved food. DEHA is a suspected carcinogen.

In a 1987 study of home use of PVC film wrap, the DEHA migration level was found to increase in proportion to the time that the food was in contact with the PVC wrap and with the rise in cooking temperature. The highest migration levels were found when the plastic film was in direct contact with food with a high fat content on it's surface. The highest migration levels were found with microwaved meats (such as pork, spareribs, and roast chicken) and bakery products(such as cake, scones, and biscuits made with peanuts). Somewhat lower levels were found in fruits and vegetables, except avocado with its high fat content. Migration levels were low when there was little or no direct contact between the food and the wrap.

In the same study, use of PVC film with foods in retail stores was examined. Results were similar. The amount of DEHA migration into foods depended on how long the film was in contact with fatty surfaces of the food. The highest amount were found in cheeses, baked goods, and sandwiches; lower amounts in cooked meat and poultry; and the lowest in fruits and vegetables.

Polyethylene, a popular plastic film used for food freezer bags and wraps, does not contain plasticizers, and is considered to be generally safe for microwaving foods. However, if printing has been applied to the surface, the primer applied to the plastic prior to printing, as well as the applied inks, may subject the heated plastic to conditions distinctly different from those for which they had been tested and approved. Only clear polyethylene is suitable for microwaving food.

Formed plastic containers, used for carry-out foods, should not be reused for microwaving. Such containers, if heated, may be subjected to conditions other than those for which they had been safety tested.

Some plastic packaging material now in use for microwaving have not been approved for use at high heat. The most severe conditions for such packaging recognized by protocols of the Food and Drug Administration (FDA) were under conditions that previously had prevailed: from 212 F to 275 F. Recognizing the changes that have occurred, FDA scientists are working with members of the packaging industry to study new testing procedures, and to learn whether packaging materials can be modified to assure food safety when used for cooking at high heat.

Of concern, too, is "active packaging." Thin layers or strips of metallic heat susceptors are placed in plastic food packaging intended for microwaving. The susceptors focus microwave radiation to produce extremely hot surfaces (400F to 500F) within the package. This high heat permits food to be browned, crisped, or popped - features usually lacking in microwave cooking. At such high heat, substances such as polymers and their breakdown products, as well as adhesives and their components and other substances present in the plastic, can migrate into the food.. Originally, susceptor strips were approved by the FDA for a different purpose and were tested at far lower temperatures.

Polyethylene terephthalate (PET) is a popular plastic film wrap. It has long been assumed that PET film provides a functional barrier to adhesive components. It was demonstrated recently that the film allowed the migration of adhesive components into foods when oil or foods were cooked in contact with it. A study by the FDA's Division of Food Chemistry and Technology showed that the susceptor board components that migrated in the largest quantities were the plasticizers rather than the polymer components, even though the polymer components were in direct contact with the oil or food, whereas the plasticizers were in the adhesive layer of the susceptor boards. Approximately 50% more plasticizers migrated than did the polymer components.

For many years, a purple dye (FD&C Violet No.1) had been used to stamp inspected meat. The dye was suspected as a carcinogen. There was no assurance that the portion of the meat with the dye would be cut away before being consumed. In 1973, the FDA banned the dye as a meat marker.

Nitrosamines (carcinogenic compounds) were discovered in rubber nipples used to cap baby bottles. The rubber was reformulated to eliminate nitrosame formation. More recently, nitrosamines were discovered in hams that had rubber netting to encase them after boning and curing. The rubber was reformulated to eliminate this problem.

With rapidly changing packaging practices and many innovative techniques, manufacturers and regulators need to be vigilant in order to prevent unanticipated and undesirable interactions with foods.

The author, Beatrice Trum Hunter, MA, has written more than 30 books on food and environmental issues, frequently before widespread public awareness. She was food editor of Consumer's Research Magazine for more than two decades. She is an honorary member of The Price Pottenger Nutrition Foundation, as well as an honorary fellow of The International Academy of Preventative Medicine and an honorary member of The American Academy of Environmental Medicine. She has been the recipient of many awards, including The Jonathan Forman Award of The Society for Clinical Ecology, The New Hampshire Society for Preventative Dentistry, and The Donnon Pepper Humanitarian Award. She can be reached at 243 Falls Road, Deering, N.H. 03244

OPTIMAL NUTRITION

 Paleodietideas.com

By Beatrice Trum Hunter
Published in Consumers' Research Magazine, July 1985
Reprinted With Permission By Author

What is an optimal diet for humans? This intriguing question is raised repeatedly, and a definitive answer remains elusive. Two recent reports from medical journals are of general interest and also deal with the question. Both describe pre-industrial diets. While we cannot return to the lifestyle of our ancestors, study of their dietary habits might contribute some insights into our own best bets where diet is concerned.

In one recent experiment, 10 Australian aborigines with diabetes agreed to return to their hunter-gatherer lifestyle. Previously, while in an urban setting on the outskirts of Melbourne, the aborigines had maintained Western lifestyles, partaking of meals that consisted, in part, of fatty meats, carbonated soft drinks and alcohol. They had become obese and had developed high blood pressure and diabetes.

Returning to the wild, they consumed only what they could obtain by hunting and fishing kangaroo,turtle, and crocodile, for example. With much activity expended in the search for food and consuming only about 1,200 calories daily, they lost their excess weight within several weeks. After two months in the wild, their blood sugar levels fell. There was significant improvement in their bodies' ability to remove sugar from the blood after eating, and they experienced a partial, and in some cases complete, reversal of adult-onset diabetic abnormalities.

These findings confirm results of other studies showing that, in cases of adult-onset diabetes, normal functioning of the insulin-secreting cells in the pancreas can be partially restored if high blood sugar levels are reduced. According to the researcher conducting the aborigine study, the main finding was that "a low-fat, low-calorie is an effective diet for control of diabetes....The low-fat content of the diet may be one of the most important therapeutic components, particularly for reducing the vascular complications of diabetes." This conclusion is remarkably similar to many of the present-day dietary recommendations for achieving and maintaining general health.

Elsewhere, the dietary habits of paleolithic  humans have come under renewed investigation. Researchers have noted that humans today "are confronted with diet-related health problems that were previously of minor importance and for which prior genetic adaption has poorly prepared us. Chronic illness affecting older, postreproductive people could have little selective influence during evolution, yet such conditions are now the paramount cause of morbidity in Western nations."  The food of "stone age" humans is regarded as having "the nutrition for which human beings are in essence genetically programmed."


Differences between the diet of our remote ancestors and that of present industrialized society have important implications for health. Increasingly, physicians and nutritionists are convinced that the dietary habits adopted by Western civilization over the past century contribute to coronary heart disease, high blood pressure, diabetes and some types of cancer. These conditions, which have become dominant health problems only recently, are virtually unknown among the few surviving hunter-gatherer populations whose food habits resemble the stone-age diet. How did some of these differences come to be?

The introduction of agriculture, a mere 10,000 years ago, radically changed human nutritional patterns. The proportion of meat in the diet declined drastically, while vegetable food came to comprise up to 90% of the total diet. As a result, people came to be considerably shorter than they had been in pre-agricultural times. Their skeletal remains show sub-optimal nutrition, both from protein-calorie deficiency and the interactions between malnutrition and infection. Since the Industrial Revolution, the animal-protein content of Western diets has become more nearly adequate. Once again, we are nearly as tall as the early, biologically modern humans. However, our diets still differ markedly from theirs, and these differences are crucial in what has been termed "affluent malnutrition."

For example, the animal protein eaten by paleolithic populations (deer,bison,horse, mammoth, etc.) differed considerably from the meat available to us in the modern supermarket. It had less total fat, more essential fatty acids ( emphasis mine) and a much higher ratio of polyunsaturated to saturated fats than ours does. The fat of wild animals contains an appreciable amount of one particular fatty acid, now being investigated for its possible property of preventing the development of atherosclerosis.(emphasis mine). Domestic beef contains nearly undetectable amounts of this valuable nutrient. Meat from free living animals contains fewer calories and more protein per unit of weight than meat from domesticated animals. Our paleolithic ancestors consumed more structural fat and less depot fat.

Foods from the vegetable kingdom reflect another difference between our ancestor's diet and ours. As foragers they ate a wide range of roots, beans, nuts, tubers, fruits and, at times, even flowers and edible gums. We have a relatively narrow variety of domesticated crops produced by horticulturists and traditional agriculturists. Furthermore, many of our domesticated plant foods have higher ratios of starch to protein than do their wild counterparts.

The paleolithic diet not only differed substantially from the typical Western diet of today, but it also differed somewhat from the recommendations currently advocated by nutritionists and federal agencies. The foods we eat are classified into four basic groups: protein foods, fruits and vegetables, dairy products and grain products. We are encouraged to have two or more daily servings from each group to achieve balance. But our ancestors who lived prior to the development of a stable agriculture of domesticated crops and animals, derived all their nutrients solely from the first two food groups. Dairy foods were non-existent, and cereal grains were rare. Yet various estimates, using modern standards, reveal that the paleolithic diet offered the health benefits of much more fiber than is now contained in a typical western diet, and the sodium intake of our remote ancestors was only one-sixth
of that present in the typical salt-laden American diet.

Of what value are these findings? The extent to which some major chronic diseases of industrialized society are related to the typical Western diet is now being critically analyzed. Evidence of linkage is accumulating steadily. Medical research in diverse fields are beginning to formulate a generally preventative diet against such conditions as atherosclerosis and cancer. The diet of our remote ancestors cannot be duplicated by us, but it can serve as a reference standard for modern nutrition as we continue to strive toward that elusive goal: achieving an optimal diet.


The author, Beatrice Trum Hunter, MA, has written more than 30 books on food and environmental issues, frequently before widespread public awareness. She was food editor of Consumer's Research Magazine for more than two decades. She is an honorary member of The Price Pottenger Nutrition Foundation, as well as an honorary fellow of The International Academy of Preventative Medicine and an honorary member of The American Academy of Environmental Medicine. She has been the recipient of many awards, including The Jonathan Forman Award of The Society for Clinical Ecology, The New Hampshire Society for Preventative Dentistry, and The Donnon Pepper Humanitarian Award. She can be reached at 243 Falls Road, Deering, N.H. 03244

HOW WELL DO WE ABSORB NUTRIENTS?

HOW WELL DO WE ABSORB NUTRIENTS?
By Beatrice Trum Hunter
Consumers' Research, April 1994
Nutrients from food are not absorbed entirely. Actually, there is a wide range of absorption, determined by many factors. The amount absorbed by depend on the form of the nutrient or other nutrients present that either increase or decrease its absorption. Or nutrient absorption may depend on factors such as efficient functioning of the gastrointestinal system, lifestyle, medications, supplements, health problems, or age. The extent of nutrient absorption may differ if food is consumed raw or cooked, or if the nutrient is derived from food or from a nutritional supplement.

The official recommended intake of nutrients acknowledges the fact that a nutrient may not be released readily from food during digestion, or may not be absorbed efficiently.. The bioavailability of vitamins and minerals varies greatly from food to food. To establish official recommendations for intake from the limited information available about most nutrients, an estimate is made and then an average value is established for the bioavailability of a nutrient from the major food sources in the diet. To compensate for low bioavailability, the recommended intake is increased.

Differences in estimating bioavailability result in a lack of uniformity in official recommended intakes in different countries. Human requirements do not differ from place to place, but food availability and food habits differ. An example is dietary iron. In many Western countries, much of the iron intake is in the form of heme iron (for example, from meat) that is well absorbed. Heme iron absorption is estimated to be about 20% to 25%. In countries where most of the iron is from plant foods (non-heme iron), iron absorption may be as low  as 2% to 8%. Because of this disparity, there may be a two-to-three fold difference in the recommended allowances for iron in different countries. For example, in Canada, where heme iron intake is high, 32 mg of iron daily are recommended for women. In India, where non-heme iron intake is high, 32 mg of iron daily are recommended for women.

Currently, there is much interest in carotene. Even with normal diets, its absorption from foods is limited. The carotene in green leafy vegetables is far better absorbed than from red or yellow vegetables. Yet even with good absorption more than half is excreted, unabsorbed.

Any condition that impairs fat absorption also impairs absorption of fat soluble vitamins, such as vitamin A and carotene. Adequate bile levels may be necessary for carotene absorption

Interactions Affect Absorption                             
Some Nutrients Increase Absorption. Non-heme iron from plant foods consists mainly of iron salts. Its absorption is influenced by its solubility in the upper part of the small intestine, which in turn depends on how the composition of the entire meal affects iron solubility. For example, non-heme iron absorption from a meal containing animal protein foods, such as meat, fish, or poultry, is about four times greater than if the major protein source is from equivalent portions of milk, cheese , or eggs. Iron absorption tends to be poor from meals in which whole grain cereals and legumes (beans) predominate. However, the addition of even relatively small amounts of a heme iron source of food substantially increases iron absorption from the total meal.

Another nutrient that increases iron absorption is vitamin C (ascorbic acid), which keeps the mineral soluble and available for absorption in the duodenum where the pH is normally alkaline.
For example, orange juice consumed with other foods increases non-heme iron absorption.

Neither human breast milk nor cow's milk is a good source of iron. Yet the low level of iron present in breast milk is relatively well absorbed by the infant, compared with iron absorption from an unfortified formula based on cow's milk. This relatively good absorption, even when the level is low, may explain why the breast-fed infant is less vulnerable to iron deficiency than an infant fed unfortified formula. Additional beneficial nutrient relationships follow:
* Magnesium helps to convert thiamine to its biologically active form.

* Phosphorus intake strongly enhances the metabolism of vitamin B

* Copper absorption averages only about 30% of the intake. Absorption is increased by acids. Copper is absorbed in the stomach and the duodenum.

* Selenium and vitamin E enhance each other. Their respective mechanisms of action are closely related. A deficiency of one may be relieved by the other.

* Absorption of vitamin A is improved when emulsified. Vitamin A is well absorbed in milk because the fat is emulsified in the liquid.

* Vitamin D promotes calcium absorption and facilitates magnesium absorption in the intestine.

* Calcium absorption requires the presence of bile salts, bile, and adequate but not excessive dietary fat. Calcium must be soluble to be absorbed. Acids, such as the stomach's hydrochloric acid, as well as ascorbic and citric acids, and some amino acids, such as glycine and lysine, can increase calcium's solubility and thus increase its absorption. Lactose, the milk sugar, also helps the absorption of calcium from milk.
                                                                                                                  
Some Nutrients Decrease Absorption. Some nutrients, especially if taken in excess, can decrease the absorption of other nutrients. For example, excessive calcium decreases the absorption of iron, phosphorous, magnesium, zinc, and manganese. Excessive calcium may also interfere with vitamin K synthesis and/or its absorption.
   * High intake of phosphorous-rich foods, such as meats, grains, potatoes, and soft drinks or other manufactured foods to which phosphorous compounds are added, decrease calcium absorption.

   * Inorganic iron is antagonistic to vitamin E. The inorganic iron combines with vitamin E in the gut and renders the vitamin inactive. This form of iron is found in fortified cereals, enriched flours, and in mineral supplements.

   * Zinc absorption can be decreased by excessive calcium, copper, folic acid, iron, and phytates.

   * Copper absorption can be decreased by excessive zinc or calcium. Copper availability is inhibited by molybdenum in combination with sulfate, which blocks absorption and/or increases its excretion.
   
    * Excessive dietary fiber, decreases the absorption of calcium and zinc.

    * Oxalates and phytates, naturally occurring compounds present in many plant foods, decrease the absorption of minerals, such as calcium and zinc.

    * Iron absorption is decreased by soy, coffee, or tea.

    * Excessive sugar consumption decreases calcium absorption and increases the urinary loss of chromium.

    * Excessive fat consumption decreases calcium and magnesium.

    * A high intake of vitamin E may reduce the intestinal absorption of vitamin K, and decrease the effectiveness of this vitamin in its role as a blood coagulant.

A Special Case. Vitamin D has a unique method for absorption. By exposing the human skin to the sun, this vitamin can be absorbed, provided ample time is allowed for the fat on the skin to help absorb the vitamin. Swimming or showering directly after exposure to sunshine, for example, interferes with vitamin D's absorption from sun exposure.

In the animal kingdom, birds obtain vitamin D by preening themselves with oil from the preen glands of their beaks and spreading it over their feathers that have been exposed to the sun. Removal of the preen glands makes birds more susceptible to rickets, a vitamin D deficiency disease. Similarly, the fur of animals appears to be a place where vitamin D is formed. Rats prevented from licking their fur become deficient in vitamin D. The incessant washing of cats for cleanliness, or the practice of monkeys grooming each other to hunt for fleas. also may provide a means for obtaining enough vitamin D to meet their requirements.

We absorb vitamin D, too, from foods of animal origin, and from fortified foods. Vitamin D has been shown to be well absorbed from nutritional supplements.

Other Interactions
Lifestyle Factors.  Caffeine intake decreases absorption of calcium, magnesium, phosphorous, potassium, and sodium. Increased excretion of these minerals is in the urine.

Alcohol intake is especially damaging to the mucosal lining of the intestine and contributes to deficiencies of many nutrients. In the alcoholic, absorption, especially of thiamine and folic acid, is impaired due to decreased intestinal function. Other depleted nutrients include other B fractions, such as riboflavin, niacin, pyridoxine, and B12, as well as ascorbic acid, fatty acids, and electrolytes. Smoking reduces calcium absorption. Also, it reduces substantially the possibility of absorbing calcium from a nutritional supplement.

Undue physical and emotional stresses can reduce calcium absorption and result in unexplained dumping of calcium in the intestinal tract. In times of worry and tension, fecal calcium excretion may be twice that of the dietary intake. Ascorbic acid, too, is lost by undue stress.

Over-The-Counter Drugs.  Mineral oil, used to relieve constipation, hinders the absorption of fat-soluble vitamins A, D, E , K, and beta-carotene. In tests, mineral oil, given in large doses along with vitamin A, interfered with the absorption of the vitamin. Much of the vitamin A was dissolved in the mineral oil, rendered unavailable, and excreted. Beta-carotene, too, dissolves in mineral oil and becomes unavailable for absorption. Other laxatives may cause calcium and vitamin D losses.

Antacids, from magnesium and aluminum hydroxide compounds, can impair calcium absorption. The pH of the small intestine is altered by antacids and, in turn, decreases absorption of folic acid and vitamin B12.

Prescription Drugs. Drugs can affect nutrient absorption in different ways, by absorbing the nutrient, impairing its absorption, or changing its characteristics. The nutrient may be rendered insoluble, or have its pH altered. These changes may result in nutrient malabsorption by producing maldigestion, or impair the functioning of the mucosa lining.

Health Problems.  Some diseases may decrease or delay absorption of nutrients. For example, evidence of decreased absorption of vitamin A is based on its level found stored in the blood of a living patient, or measured in the liver after death.

Chronic constipation impairs absorption of vitamin A and carotene.

Ascorbic acid (vitamin C ) is absorbed from the small intestine. A number of food-borne pathogens, such as Salmonella and Escherichia coli, not only result in food poisoning, but also decompose ascorbic acid. In patients with gastrointestinal problems, such pathogens prevent ascorbic acid absorption.

Abnormal conditions in the intestinal tract, such as diarrhea, decrease arterial absorption of ascorbic acid, even when this vitamin is administered in high dosages. Also, ascorbic acid absorption may be impaired in patients with achlorhydria (an absence of a normal supply of hydrochloric acid from gastric secretions).

Any health condition that impairs fat absorption also impairs absorption of vitamin A and carotene.

Riboflavin is not absorbed readily by patients with gastrointestinal diseases. This vitamin is absorbed from the intestine and requires hydrochloric acid for its absorption. However, injected riboflavin is utilized by patients with gastrointestinal diseases. Given intravenously, most of the riboflavin goes into the small intestine, especially the duodenum, from where it can be reabsorbed. Most riboflavin is destroyed in the large intestine and in its passage through the kidney.

Individuals who lack bile in the intestine due to poor secretion of bile salts or obstructive jaundice (due to stones, cancer, or abnormal narrowing of a duct or passage) may have poor intestinal absorption of vitamin K.

Age.  The age of an individual may play a role in nutrient absorption. For example, by examining fecal secretions, it has been found that vitamin A is poorly absorbed in infants, but well absorbed in adults. Also, infants and children absorb or convert carotene very poorly.

The gastrointestinal tract of children differs from adults in permeability, pH, transit time, and enzymatic activity. Children may absorb nutrients well or poorly, depending on the balance of these factors.

Calcium absorption is affected, in part, by the body's needs during different periods. If the need is low, calcium absorption from the intestine may be low. During periods of growth, pregnancy, and lactation, calcium needs are high and its absorption may increase greatly.

Iron absorption, like calcium, is affected, in part, by the body's needs during different periods. If iron stores are low, which is common for most women and children, the intestinal mucosa readily takes up iron and increases the proportion absorbed from the diet.  Conversely, high iron stores, typical of men and most post-menopausal women, reduce the percentage of iron absorbed, which helps prevent iron overload.

The elderly may experience impaired B12 and calcium absorption in the intestine as well as other nutrients. As people age, many systems may function less efficiently than when they were younger.

Raw Versus Cooked Foods.  It might be assumed that more nutrients are absorbed from raw than from cooked foods because the heat and pressure of cooking destroys certain nutrients. This assumption is true for some, but not for all foods. Anti-nutrients, present in some raw foods, are deactivated by cooking, and therefore nutrients are available for absorption. For example, tests showed that less vitamin C was obtained from raw than from cooked broccoli.

Years ago, experiments were conducted to determine carotene absorption from carrots. Results were mixed. One of the investigators found that 20% of the carotene in raw carrots was absorbed, compared to only 5% in cooked carrots. A second investigator had opposite results. Absorption in the raw carrots was only 1%, compared with 19% in the cooked carrots. Then, a third investigator showed that about 25% of the carotene absorbed was doubled if the carrots were pureed. These studies show the difficulty in establishing whether raw or cooked vegetables provide better nutrient absorption.

Supplement Absorption

Generally, for good absorption of nutritional supplements, they should be taken along with foods at meals. However, there are exceptions.

Iron supplements are absorbed best if taken on an empty stomach. Iron absorption is impaired if hydrochloric acid is deficient in the stomach. Iron supplements should not be taken at the same time as vitamin E supplements, for iron and vitamin E are antagonistic to each other.

Zinc supplements, if taken with egg, milk, or cereal, are not as well absorbed as when they are taken with other foods..

Inorganic forms of minerals may not be well absorbed. To improve absorption, manufacturers may chelate mineral supplements. This technique binds the mineral to an organic chelating substance that mimics the absorption process in the body. Examples of inorganic forms of minerals are carbonate, chloride, hydroxide, iodide, oxide, phosphate, selenate, selenite, and sulfate. Examples of organic chelated  forms of minerals are ascorbate, aspartate, citrate, gluconate, glycinate, lactate, orotate, and any substances that end with the word "chelate."  The chelated form of a mineral supplement may be a more expensive product than the inorganic form. However, it may be more cost-effective because of its improved absorption.

Calcium supplements cannot be absorbed unless they disintegrate and dissolve. According to standards established by the U.S Pharmacopeia, 75% of a drug tablet must disintegrate within a half hour. However, calcium tablets are regarded as nutritional supplements, not drugs. There has been no requirement that they meet this protocol. The Food and Drug Administration (FDA) has not required such testing for calcium or for other nutritional supplements.

In 1988, Dr. Ralph F. Shangraw, chairman of the Department of Pharmaceutics at the School of Pharmacy, University of Maryland, reported results of experiments he had conducted with calcium supplements. He found that many calcium tablets had poor disintegration and dissolution, which would indicate that the product might be absorbed poorly, if at all. As a result of Shangraw's findings, some manufacturers reformulated their calcium supplements to improve disintegration and dissolution of their products.

A simple tests roughly simulates how effectively a calcium supplement is apt to disintegrate and dissolve in the presence of hydrochloric acid in the normally functioning stomach. Place a calcium tablet in vinegar and stir occasionally. After a half hour, at least three fourths of the tablet should be dissolved. If this has not occurred, it suggests that the supplement will be absorbed poorly, if at all.

Foods Versus Supplements.  Surprisingly, comparison data are largely lacking for nutrient absorption from foods with that from supplements.

Recently, a study was conducted by researchers at the USDA's Human Nutrition Research Center in Beltsville, Maryland, comparing the absorption of vitmain C from foods with that from vitamin C supplements. Sixty-eight men were placed on a diet designed to be very low in vitamin C to deplete them of this nutrient. After one month, the diet was supplemented with vitamin C-containing foods or supplements. Both foods and supplements were equally effective in restoring plasma vitamin C levels, with the exception of raw broccoli. In a raw state , broccoli was at least 20% less effective in raising plasma vitamin C levels than other foods that contain significant amounts of vitamin C.

Unlike vitamin C, it is far more difficult to obtain extra vitamin E from foods. According to Orville A. Levander, from the Beltsville center, it is virtually impossible to obtain more than 25 International Units (IUs) of vitamin E per day solely from the diet. The U.S. RDA is 15 IU of vitamin E for men and 12 IU for women. Levander reported that the average intake is about 10 IU to 15 IU. In recent years, higher levels have been suggested for health maintenance or treatment of diseases.

Levander and his colleagues studied 65 men for a comparison of how diets and supplements contribute to plasma levels of vitamin E. The group of men depending on vitamin E absorption solely from food showed no significant differences in their blood levels. The average daily intake was less than 20 IU of vitamin E from dietary sources. However, the group of men who added a multivitamin supplement at least every other day were able to obtain an extra 15 IU to 60 IU of vitamin E daily. In the third group, the men who took daily vitamin E capsules were able to obtain at least 100 IU of vitamin E above their dietary intake.

Compared with the group that did not take supplements regularly, plasma vitamin E levels averaged 14% higher  in the group taking multivitamin supplements.. However, the levels were more than twice as high in the group taking vitamin E supplements daily.

The researchers suggested that persons who desire to increase their vitamin E plasma levels substantially need to take supplements.

At times, a nutrient may be absorbed more effectively from a supplement than from a food source.  In a recent study of the Human Nutrition Research Center on Aging at Tuft's University, as well as from other studies, it was found that 20% to 40% of the elderly lose their ability to absorb the protein-bound nutrient, vitamin B12 from food. However, they were able to absorb the crystalline form from a supplement.

The answer to the question "how well are nutrients absorbed?" is far from simple. The basics of good nutrition offer the best possibilities. These basics have been stated frequently but bear repetition. Eat a wide variety of basic foods, avoid excesses to minimize imbalances, and improve lifestyle factors related to health. All these factors contribute to better nutrition.


Selected Drug Interactions

PREDNISONE, and other gluco-corticoids, used with allergies and collagen disease, can impair calcium absorption. Other drugs that can impair calcium absorption include anticonvulsants, such as phenobarbital, diphenylhydantoin, and primidone; sedatives from glutethimide; and diphosphonates, used with Paget's disease.





CHOLESTYRAMINE, a cholesterol-lowering drug, may induce steaorrhea (excessive fat in the feces) and malabsorption of fat-soluble vitamins, as well as interfere with the absorption of folic acid, iron, and vitamin B12.

CIMETIDINE, used with duodenal ulcers, as well as slow-released potassium drugs,used with high blood pressure, reduce vitamin B12 absorption.
BIGUANIDES, used as hypoglycemic agents with diabetes, may result in vitamin B12 malabsorption.
COLCICHINE, used with gout, may interfere with the absorption of vitamins K and B12, carotene, sodium, lactose, and fat.
NEOMYCIN, an antibiotic, may decrease absorption of vitamin B12, calcium, iron, potassium, sodium, nitrogen, fat, lactose, and sucrose.
PARA_AMINO SALICYLIC ACID, used with tuberculosis, may interfere with the absorption of vitamin B12, folic acid, and fat by the mucosa.
POTASSIUM CHLORIDE, used as a salt substitute, may interfere with vitamin B12 absorption.
SALICYLAZO-SULFPYRINE, used as an anti-inflammatory agent with ulcerative colitis and regional enteritis, interferes with absorption of folic acid by the mucosa.


ON THE OTHER HAND, certain foods can speed up or slow down the body's absorption of the drug and influence the efficacy of the drug. Follow directions given by your doctor or pharmacist.
FOODS HIGH IN VITAMIN K (such as liver and dark green leafy vegetables) interfere with the action of anticoagulants that prevent blood clots.

CALCIUM-RICH FOODS (such as dairy products) reduce the effectiveness of tetracyclines used to fight infection.
CAFFEINE-CONTAINING DRINKS (such as coffee, tea, and cola) as well as acidic fruit and vegetable juices (such as orange, grapefruit, and tomato juices) may destroy some drugs in the stomach before they can perform their work.

HIGH FIBER FOODS (such as whole-grain products) may reduce drug absorption in the body.

The author, Beatrice Trum Hunter, MA, has written more than 30 books on food and environmental issues, frequently before widespread public awareness. She was food editor of Consumer's Research Magazine for more than two decades. She is an honorary member of The Price Pottenger Nutrition Foundation, as well as an honorary fellow of The International Academy of Preventative Medicine and an honorary member of The American Academy of Environmental Medicine. She has been the recipient of many awards, including The Jonathan Forman Award of The Society for Clinical Ecology, The New Hampshire Society for Preventative Dentistry, and The Donnon Pepper Humanitarian Award. She can be reached at 243 Falls Road, Deering, N.H. 03244


                                                                                                        

SHOULD EVERYONE CUT BACK ON SODIUM?

By Beatrice Trum Hunter
From Consumer Research Magazine
Feb. 1995

In 1994 the U.S Department of agriculture proposed to limit sodium in school feeding programs. The Salt Institute, a trade organization, promptly protested. The group contended that removal of high-sodium foods, such as fluid milk and other dairy products, inevitably denies children other important nutrients such as calcium and potassium, present in such foods.

This challenge deserves scrutiny. The USDA's proposal, which forms public policy, must be based solidly on scientific evidence. Correct? Incorrect!

Contrary to popular perception, universal sodium restriction is unnecessary, and possibly undesirable. A common notion is that sodium induces hypertension (high blood pressure) and lowering sodium intake will prevent hypertension. Unfortunately, this scientific notion has no scientific basis. Instead, many recent medical studies have brought into question the effectiveness and even the safety of universal sodium restriction.

There is a relationship between sodium and blood pressure, which is important for about 10% of the population that is sodium-sensitive. For this group, sodium restriction is an important feature, along with other measures, for treatment. However, for about 90% of the population, there is no convincing scientific basis for the idea that sodium restriction will prevent hypertension.

Treatment Differs from Prevention. In earlier times, medically supervised sodium restriction therapy was common with hypertensives, For the general public, however, the Food and Nutrition Board of the National Academy of Sciences warned in 1954 that "harmful results may follow the restriction of sodium intake... when the diet is severely restricted in sodium for long periods,...reduction of intake of essential nutrients, especially vitamins, may occur...(in studies) calcium, riboflavin, and protein were the principal nutrients in short supply. These dietary deficiencies were occasioned chiefly by the omission of milk....Metabolic studies on patients with hypertension treated with sodium-restricted diets have revealed a number of changes....these changes are potentially dangerous, perhaps leading to... reduced renal (kidney) function."

At that time, there was a medical consensus regarding the treatment of hypertension. In terms of prevention, one doctor warned the public against self-imposed sodium restriction that "affords no benefit to the normal individual....self restriction will not prevent disease."

Another doctor noted that "thousands of misguided enthusiasts have eaten unpalatable food on a mistaken assumption that....high blood pressure would be prevented. The facts are simple. There is no evidence that excessive salt intake produces high blood pressure in humans."

Treatment focuses on an individual's medical problems, with all the unique characteristics that shape the person. Prevention focuses on entire populations and improvement of their average conditions. The medical and public health models differ. Physicians dealing with a patient follow the rule of "do no harm", whereas public health doctors hope to "do some good."

The Sodium Hypothesis. In the late 1950s, the difference between treatment and prevention of high blood pressure became blurred. Lewis K. Dahl, M.D. promoted the hypothesis that there was a direct correlation between sodium intake of populations and hypertensive incidence.

Dahl's sodium hypothesis was viewed by critics as being "packaged as a panacea." A few strategically placed advocates popularized the hypothesis. Over time, and with endless repetition, the hypothesis gradually was viewed as gospel.

There were skeptics. In a 1979  report, the National Institutes of Health Hypertension Task Force noted that the brevity of the section on prevention"is indicative of the lack of knowledge concerning basic mechanisms of hypertension. Research must supply new knowledge before confident statements concerning prevention can be made."

John H. Larach, M.D., a prominent hypertension researcher, commented in 1983 on the popular anti-sodium policy:
"Now, what can I possibly have against these well-intended efforts? Nothing except the fact that they are not supported by scientific evidence. They are based on assumptions that are either entirely false or entirely unproven. Let us review some of these. First assumption: Everyone who has high blood pressure should cut back on salt to bring the pressure down. This is wrong......  Second assumption: Hypertension can be prevented in normal people if they cut down on their salt intake while they're still healthy.
This theory sounds good and conforms to the attractive idea of preventing disease by changing our diets and life-styles. The trouble is, there is not a shred of evidence to support it where high blood pressure is concerned. Not even a badly designed, poorly executed scientific study.
In 1984, a group of 13 scientists wrote on the subject in The Lancet:: "The usual scientific standards for weighing evidence and for giving advice which are now well established in drug development and prescribing seemed to have been forgotten in an evangelical crusade to present a simplistic view of the evidence which will prove attractive to the media."

Larach, joined by Michael H. Alderman, M.D. assessed the impact of sodium intake on cardiovascular health among healthy people over the course of eight years. In 1991 they reported their finding. People on low-sodium diets had dramatically higher numbers of heart attacks.

Another skeptic of the sodium hypothesis was David A McCarron, M.D. at the Oregon Health Sciences University. He argued that governmental concern about high-sodium diets was misplaced. Not an excess of nutrients such as sodium is the problem, but rather a deficiency of nutrients, especially calcium, is responsible for hypertension.

McCarron's "calcium hypothesis" reflected a renewed interest in the interaction of electrolytes-- electronically charged particles that play an important role in regulating body processes--mainly the interrelationships of sodium with calcium and potassium. Numerous articles in medical journals noted that calcium and potassium deficiencies were implicated in sodium's blood pressure effects. Some studies found them to be even more important than sodium.

Unanticipated Risks
Researchers began to question, too, the lack of proven safety for universal sodium restriction. Studies began to identify unanticipated risks of low-sodium diets, resulting in elevated blood pressure in some individuals, and increases in serum creatinine (a waste product from a substance found in muscles, blood, and urine). Also,there was a rise in undesirable low-density lipoprotein cholesterol, uric acid and significantly higher fasting insulin levels. All of these features are disease risk factors.

In addition, low-sodium diets might lead to a reduced capacity to absorb other nutrients and a lowered resistance to problems such as diarrhea, hyperthermia, and bleeding. Low sodium diets also seem to be related to sleep disturbances.

The sodium hypothesis proponents recognized that their scientific basis was being challenged. They devised a massive global study in an attempt to answer the skeptic's objections. INTERSALT was funded by national blood pressure research groups, the National Heart, Lung, and Blood Institute, and the World Health Organization, in an attempt to provide a scientific basis for the sodium hypothesis.

By 1986, INTERSALT researchers had examined numerous population studies purported to link sodium and hypertension. The studies encompassed more than 10,000 individuals, at 52 centers, in 32 countries. Most of the studies, when evaluated, were found to be flawed, and were discarded. The number of quality studies was reduced to 13, of which 10 failed to demonstrate any sodium-hypertension association. The results of the evaluation were summarized succinctly in the British Medical Journal: "Salt has only small importance in hypertension."

Thomas J. Moore, a medical writer, wrote that the INTERSALT results were "as clean an outright refutation as can be found in science, yet the findings of the INTERSALT  study passed virtually unnoticed in the media and scientific journals in the United States."

According to Moore, John Larosa, then head of the American Heart Association's Nutrition Committee, a group which regularly endorsed sodium restriction, admitted that " we're trying to figure out how to back away from the salt recommendation without looking like fools."

William Ira Bennett, M.D., editor of the Harvard medical School Health letter, explained that the deafening silence by officials was because they had invested their credibility in promoting the sodium hypothesis. Bennett wrote that"little was said about the INTERSALT study because it was a kind of humiliation when you have a nutrition recommendation that you have to abandon."

Despite the lack of any confirmation of the sodium hypothesis from the INTERSALT study, federal officials continue to retain the recommendation that everyone should reduce dietary sodium.  The 1988 Surgeon General's Report admitted that whether universal sodium restriction would lower population blood pressure or not had never been tested.

Recognizing that the public policy was at odds with scientific findings, the National Heart, Lung, and Blood Institute convened a Salt and High Blood Pressure Workshop in 1989. The experts could reach no consensus.

The leaders of the INTERSALT project tightly controlled the release of analyses of the data base for publication. They used meta-analysis, a technique of compiling all previous studies to gain the statistical power of large numbers of observations. However, the poor quality of many of the early studies, as already noted, was ignored, and the meta-analysis by sheer numbers was used to confirm the sodium hypothesis.

The advice for hypertensives to decrease sodium intake remains sound. However, the same advice for the general public lacks a scientific basis. There is no proof, to date, that excess sodium intake will prevent hypertension from developing.

Even when findings are positive about sodium intake, the firmly entrenched sodium hypothesis overrides other considerations. In recent studies with the elderly, sodium intake had a small beneficial effect on bones (the ultra distal radius and total hip) in men. Nevertheless, the researchers felt obliged to caution that "there are many overriding public health reasons not to increase sodium intake."

Support of the sodium hypothesis is based on population studies, which ignore the confounding variables that may determine sodium's role in hypertension. Precisely how sodium influences blood pressure is not yet firmly established.

Many Contributing Factors
There are many determinants of hypertension. Sodium appears to be only a minor player in a highly complex field. There are environmental factors of geography, location, temperature, and poisoning from heavy metals, such as lead and cadmium.

For example, cadmium, a toxic metal, is an important contributing cause of hypertension. With age, cadmium accumulates in the body, especially in the kidneys, from contamination of this heavy metal in the environment. Cadmium in food results mainly from food processing and refining; in drinking water, from areas of "soft" water lacking in minerals such as calcium and magnesium, as well as from water piping; and in air, from industrial pollutants. Cadmium's role in hypertension can be stopped if the body's zinc supply is adequate. Unfortunately, many Americans are low in zinc.

There are lifestyle factors of obesity, lack of exercise, mental stress, smoking, alcohol, coffee and tea. Hypertension is far more common among overweight adults than among those with normal weight. Studies have shown that weight loss can reduce blood pressure significantly in obese adults. Heavy drinking is known to increase hypertensive risks. Even moderate drinking may be a risk factor, according to the findings of Jacqueline Witteman and colleagues at Harvard University. They found that women who consume two mixed alcoholic drinks daily may be 40% more likely than others to develop hypertension. Milk drinkers may lower this risk, possibly due to the calcium and other protective nutrients in the milk.

There are factors of genetics, race, gender, hormones and age. A hormone has been identified and studied that is believed to be related to hypertension development. A sodium-pump inhibiting hormone appears to slow the activity of a protein that moves sodium out of the cells, according to Mordecai P. Blaustein, M.D. and John Hamlyn, Ph.D. at the Maryland School of Medicine.

There are nutritional effects of certain dietary components, and potable water quality. Studies that examine only sodium or any other single dietary component as a factor in inducing hypertension give too limited a view. Many components may be interrelated. Also, not all sodium compounds affect blood pressure as does sodium chloride (table salt). Nor do we eat sodium, per se, but rather as sodium compounds in foods.
Nutritional Factors. Hypertension is associated with certain nutritional deficiencies, especially with low intake of specific minerals, vitamins, proteins, fatty acids, carbohydrates, and calories. Excessive sodium intake is related to some of these nutrients.

Dr. McCarron and his colleagues suggest that nutritional deficiencies, not excesses, distinguish hypertensive and overweight Americans in studies, individuals on low-sodium diets with low intake of dairy products were at two to three times greater hypertensive risk than those with high intake of dairy products. McCarron concluded that the standard weight-reduction diets actually may exacerbate conditions that lead to hypertension by further reducing nutrients that are essential to maintain normal blood pressure. By recommending sodium reduction, McCarron said, "we're setting up the dietetic community for failure."

Many Americans do not get enough calcium. McCarron believes that a lack of adequate calcium may be as important a factor in hypertension as is excessive sodium and that sodium-sensitive individuals may benefit the most by increasing calcium intake.

The ratio of potassium to sodium intake is important. Basic foods have favorable high potassium/low sodium ratios. Examples are fresh fruit and vegetables. This ratio becomes inverted in processed foods, whereby the potassium is reduced or even depleted, and sodium rises, sometimes dramatically. Examples are canned string beans and potato chips. In industrialized countries, the average diet contains a large excess of sodium-far beyond the physiologic needs. Processed foods account for up to 80% of the daily sodium intake in the American diet.

The long held belief that sodium is the sole salt component responsible for increasing blood pressure has been challenged. Studies suggested that the chloride component in sodium chloride (table salt) might also be a factor. In rat studies, blood pressure increased far more following ingestion of sodium chloride than with other sodium-containing compounds. Chloride might enhance sodium's effects on blood pressure.

Although table salt may increase blood pressure in hypertensives, many other sodium-containing compounds may not. In a study conducted by Dr. Theodore W. Kurtz and his colleagues at the General Clinical Research Center, University of California, men with high blood pressure were given table salt supplements for a week. As anticipated, their blood pressure rose sharply. But, when they received the same amount of sodium in other sodium-containing compounds, such as sodium citrate (a common additive in many foods and beverages) their blood pressure remained constant.

A clearer designation would be "sodium chloride-dependant hypertension" rather than "sodium-dependant hypertension."

Many Americans have diets low in magnesium. Burton M. Altura, M.D. at SUNY, Downtown Medical Center (Brooklyn) reported that low magnesium levels may be related to hypertension. A group of normal rats, fed a magnesium-deficient diet for 12 weeks, developed hypertension. The interior of the fine branches of their veins and arteries had constricted in size, which caused the blood pressure rise. The lower their intake of magnesium, the smaller their blood vessels became, and the more their blood pressure rose.

In human studies conducted in The Netherlands, 91 middle-aged and elderly women with untreated mild to moderate hypertension were given magnesium supplements at levels difficult to achieve solely by dietary changes. After 6 months, they showed beneficial blood pressure reduction.

Some segments of the American population may be severely magnesium depleted, including chronic alcoholics, and individuals taking diuretics-widely used prescription drugs. The diuretics, used by hypertensives to expel sodium, also expel magnesium. A Swedish study found patients given a magnesium supplement along with the diuretic avoided this problem.

Tin may be a factor, not yet well recognized, in hypertension. The animal model used most frequently used to study hypertension is a spontaneously hypertensive rat (SHR). In tests, a tin compound (stannous chloride) was found to keep blood pressure normal in the young SHR during a 14 week study, but had no similar beneficial effect on SHR adults. Selenium deficiency has been found to accelerate the development of hypertension in SHR.

In epidemiological studies, as well as in animal experiments, an adequate intake of high-quality protein food has been shown to be beneficial for sodium excretion, improvement of arterial walls, and lowering of blood pressure.

The type of fat in the diet may be related to hypertension. In a review of non-drug therapies for hypertension, reduction of saturated fat intake was recommended in the American Journal of Hypertension (February 1989). This dietary change causes a modest lowering of blood pressure, as well as counteracting the cholesterol-raising effect of some commonly used hypertensive drugs. Vegetarians and others whose fat intake consist mainly of polyunsaturated fats have lower blood pressure levels than those whose fat intake consists mainly of saturated fats.

The American diet is low in omega-3 fatty acids, found in fish and in fish oil supplements. Increased fish consumption may reduce the risk of pregnancy-induced hypertension. Results have been inconsistent with many studies using a high fish diet or fish oil supplements to reduce high blood pressure. However, data from studies of  more than 1,300 subjects, analyzed by scientists under the auspices of the national Institute of Environmental Health Science of the National Institutes of Health, suggested overwhelmingly that fish oil lowered blood pressure moderately in the majority of hypertensive subjects. Generally larger amounts of fish oil produced greater declines in blood pressure than did smaller amounts. Very low supplemental dosages had virtually no effect. Nor did it produce changes in the blood pressure level of healthy subjects. The effects of fish oils, however, might be harmful for hypertensives with impaired kidney function or poor blood clotting ability.

Sugar is a food component that, at high intake, is known to enhance the increase of blood pressure caused by salt in sodium-sensitive rats. In a study involving monkeys, larger amounts of sugar as well as salt in the diet, induced high blood pressure. The animals fed a diet containing 3% salt and 38% sugar developed higher blood pressure than those on a high salt, but sugarless, diet. Both groups developed higher blood pressure than animals fed their normal monkey chow. The study demonstrated that a diet high in both sugar and salt--much like a typical American diet-- also could raise the cholesterol level in the animals' blood.

Deficiencies of certain nutrients and food components may be additional factors in hypertension. These constituents include some vitamins (A, B3, C, and biflavonoids);certain amino acids (tyrosine and tryptophan); and inadequate intake of water and dietary fibers. Food allergy, especially gluten sensitivity to certain grains (wheat, rye, oat and barley) has been suggested by Lloyd Rosenvold, M.D. of Loma Linda University Medical School as an unrecognized factor in some cases of hypertension. There may be other nutritional factors, as yet unrecognized, that play a role in hypertension.

Continuing A misguided Policy?
The national High Blood pressure education Program Coordinating Committee met late in 1994 to formulate "prevention" strategies in the national campaign against hypertension. Some participants raised doubts about the initiative. Mary C. Winston of the American Heart Association noted the mounting opposition, "by a lot of good scientists," to sodium restriction as a preventative measure.

At the committee meeting, H. Mitchell Perry, Jr. of Washington University in St. Louis said, "I don't think the scientific evidence supports a public health campaign of this type."

James R. Sowers, M.D. of Wayne State University urged the committee to recognize that "we are not just making progress on salt." Sowers urged that more attention be given to the multiple risk factors involved in hypertension.

Despite such criticisms, the Coordinating Committee staff reported that an extensive media campaign is already under way.

In conclusion, the evidence suggests that for 90% of the population, with blood pressure within normal range, sodium intake does not cause hypertension. As with all nutrients, "moderation" is a key concept. Also, sodium intake must be balanced by intake of foods with adequate amounts of potassium, calcium, and other nutrients related to it. People are most likely to achieve both moderation and balance by selecting basic foods - fruits, vegetables,meat, fish, eggs, and dairy foods. Public health policy aiming at narrow dietary recommendations tend to obscure this sound advice. When the policy lacks scientific basis, it may actually undermine it.

Photo By Peter Beard

 The author, Beatrice Trum Hunter, MA, has written more than 30 books on food and environmental issues, frequently before widespread public awareness. She was food editor of Consumer's Research Magazine for more than two decades. She is an honorary member of The Price Pottenger Nutrition Foundation, as well as an honorary fellow of The International Academy of Preventative Medicine and an honorary member of The American Academy of Environmental Medicine. She has been the recipient of many awards, including The Jonathan Forman Award of The Society for Clinical Ecology, The New Hampshire Society for Preventative Dentistry, and The Donnon Pepper Humanitarian Award. She can be reached at 243 Falls Road, Deering, N.H. 03244