Vitamins, minerals can prevent disease – column
Mary Jane Dittmar
Vitamins, Minerals Can Prevent Disease
In recent years, well-coordinated media campaigns spearheaded by the “nutrients-as-preventatives” skeptics have been downplaying the benefits of nutritional supplements and exaggerating their potential for danger. We are warned periodically by the Food and Drug Administration, the American Medical Association and the American Dietetic Association, among others, that taking supplements is dangerous and a waste of money, since most Americans are not poorly nourished.
Actually, nutritional supplements have proved to be less toxic than many FDA-approved prescription and over-the-counter drugs. An average of only four cases of toxicity from vitamin A, which is one of the nutrients that can be toxic when taken in excessive amounts, are reported every year. Research has shown that a daily dose of 100,000 International Units (I.U.) of vitamin A given to adults for months has produced no ill effects and that 100,000 to 150,000 I.U. of vitamin D must be given daily for several months before adults can experience toxic side effects. The B vitamins have been reported to be relatively nontoxic.
The Food and Nutrition Board has found that a daily intake of 18,000 times the Recommended Dietary Allowance (RDA) for vitamin E taken daily for five months has not produced symptoms of toxicity. Vitamin E should, however, be used with caution by people who have hypertension or a rheumatic heart, since it improves the efficiency of the heart and can temporarily raise the blood pressure and increase the imbalance between the two sides of the heart. In general, reports on toxicity of most vitamins indicate that most adults can take all vitamins in amounts several times the RDA without side effects.
Nutrients As Disease Fighters
The following excerpts from Current Concepts and Perspectives in Nutrition, published by The New York Hospital-Cornell Medical Center Memorial Sloan-Kettering Cancer Center, illustrate the expanded roles researchers have been identifying for individual nutrients.
“The emphasis on dietary prevention of cancer is likely to become increasingly important in future years as our understanding of the relationship of nutrition to the process of carcinogenesis increases . . . . Clinical evidence of possible relationships between nutrition and cancer has been derived from several lines of investigation. Epidemiologic studies relate specific components in the diet, including individual nutrients, to relative risks of developing particular cancers in a given population. . . .”
Among the nutrients cited:
* Vitamin C: “It may inhibit stomach tumors that might develop through the action of nitrosamines by acting to diminish nitrosamine formation. It has been shown to inhibit the induction of tumors by nitrosamines in rats . . . . The available evidence about the inhibitory effects of ascorbate on nitrosamine and nitrosamine formation from nitrite under conditions prevailing in the stomach suggests that vitamin C perhaps should be consumed at each meal, since the effects of the vitamin are of relatively short duration . . . . Foods containing vitamin C may be adequate for this purpose.”
* Vitamin A: “Studies reveal that vitamin A-deficient animals show greater susceptibility to epithelioid cancers of the colon, lung, bladder and other organs in the presence of chemical carcinogens and viral agents . . . .”
* Vitamin E: “This nutrient reduces oxidant damage to the lung epithelium of animals exposed to ozone, cigarette smoke or other toxins, and decreases the frequency of chemically induced tumors in some animal model systems . . . . Recent epidemiological data, moreover, support an association between low levels of serum vitamin E and increased risk of lung cancer in human populations . . . . Therefore, concern has been expressed that the RDA for vitamin E as currently formulated may be inadequate to achieve optimal immune function and cancer prevention.”
* Selenium: “Although toxic at a relatively low concentration, selenium is an essential trace element that has demonstrable anti-carcinogenic properties . . . .”
* Calcium: “This mineral has shown promise for prevention of colon cancer in high-risk groups, findings which currently need confirmation and extension. . .”
* Other studies have shown that selenium can protect against the development of some cancers, including esophageal cancer. In a study by Jaskiewicz, et al., conducted among populations in southern Africa, blood selenium levels of subjects with low incidences of esophageal cancer were found to be relatively high. Populations with moderate to high incidences of this form of cancer had much lower selenium levels . . . it is suggested that selenium deficiency may play a role in the development of esophageal cancer.”
Average Nutritional Intake is Not Adequate
The evidence showing that the diets of many Americans are not providing levels of nutrients to meet the RDAs has been growing.
“The American diet is lousy and people are dying because of it,” concluded the National Cancer Institute (NCI) at the end of a longterm study which analyzed what Americans ate in a typical day. More than 11,000 people were interviewed by researchers from NCI and the U.S. Department of Agriculture (USDA). They found that in a typical day, 40 percent of Americans did not eat a single fruit, 20 percent did not eat a single vegetable and that only about 49 percent included garden vegetables (other than potatoes or a salad) in their diet daily. More than 80 percent ate no high-fiber cereals or whole-grain breads. “We really need to change the way we eat,” said Gladys Block, NCI scientist. “I really believe that could make a difference in the amount of cancer we have.”
Although the Surgeon General’s 1988 Report on Nutrition and Health contained the statement that supplements are not necessary for people who eat an adequate diet, a survey conducted by the USDA showed that only 3 percent of the population had diets that met the “four food groups” pattern and that not a single person of more than the 21,000 surveyed got 100 percent of the RDA for all 10 of the nutrients included in the survey.
As one researcher has observed: “It is commonly asserted that adequate nutrition can be obtained from a balanced diet without the need for additional supplements . . . . It is important, however, to distinguish what can be achieved and what is achieved in the usual American diet.”
Are the RDAs Sufficient?
Diets that meet the RDAs still may not provide the body with nutrients sufficient enough for optimal functioning, some researchers say. R. Buzina, et al., reported that marginal malnutrition, including subclinical vitamin and mineral deficiencies, can affect some vital functions such as physical work capacity, immunobiological competence and cognitive functions and behavior. These researchers stated their findings at a workshop held under the auspices of the World Health Organization.
Among the findings of the Buzina team were the following:
* Marginal deficiencies of iodine and iron alone are known to affect hundreds of millions of people worldwide.
* “There is evidence of some loss of physical work capacity (measured by the percent of a person’s maximum oxygen consumption required to do a task) even in marginal malnutrition; the degree of loss is related to the severity of the nutritional deficit. Iron has the clearest relationship to physical work capacity. The B vitamin complex and vitamin C have an effect on physical work capacity; and thiamine, riboflavin and perhaps carnitine appear to be particularly relevant for further study.
* “Zinc deficiency has a profound impact on cell-mediated immunity and other immune responses. Even the marginal deficiency induced in human volunteers results in impaired T-cell function . . . .
* “Mild iron deficiency . . . is associated with reversible abnormalities in immune function.
The concept of “suboptimal” nutrition was discussed in detail by Roger J. Williams, Ph.D., former president of the American Chemical Society in Biochemical Individuality. His studies revealed that biochemical individuality in the same species of animals, including humans, varies sometimes tens and hundreds of times. He explained that RDAs were set at about a 50 percent increase over the minimum daily requirement (the minimum amount of a particular vitamin necessary to prevent the occurrence of the disease associated with a deficiency of that vitamin) and that these amounts are not sufficient to account for these individual variances. He documented that enzyme deficiencies in normal individuals varied from threefold to fiftyfold, which indicates strongly that comparable increased quantities of certain vitamins also would be necessary for maximum effect. Such quantities could not be expected to be supplied by food and this could necessitate the taking of supplements.
To supplement or not to supplement? The answer to this question is not as clear-cut as the critics make it seem. The scientific evidence for taking some supplements is becoming more and more convincing.
PHOTO : Mary Jane Dittmar is well-known in the natural foods industry for her commitment to
PHOTO : upholding the principles of good health and nutrition. The former editor of Health Foods
PHOTO : Business magazine, she has held positions in the journalism, government, education and
PHOTO : public service arenas. She writes regularly for Better Nutrition on issues relating to the
PHOTO : health foods business, government regulation and institutional research projects.
REFERENCES:
Rubin, Marilyn McDevitt. “The ABCs of the RDAs.” Philadelphia Daily News, Oct. 28, 1987.
Pinsley, Elliot. “U.S. Seeks End to Vitamin Overkill.” The Record. May 18, 1986.
Kumler, Warren D. “The Case for Supplemental Vitamins.” American Pharmacy, Vol. NS19, No. 9, Aug. 19, 1979.
Jaskiewicz J., Marasas, W.F.O. and Rossouw, J.E., et al. “Selenium And Other Mineral Elements in Populations at Risk for Esophageal Cancer.” Cancer, 62:2635-2639, Dec. 15, 1988. In “R.P. Scherer Survey of Health and Nutrition Literature,” 1989, Vol. IX (2):7.
The Associated Press. “Cancer Institute American Diet Stinks.” The Record, March 13, 1988.
Buzina, R. Bates, C.J., van der Beek, J., et al. “Workshop On Functional Significance of Mild-to-Moderate Nutrition.” American Journal of Clinical Nutrition, 50:172-176, 1989. In “R.P. Scherer Survey of Health and Nutrition Literature.” July 1989, Vol. IX(7): 8.9.
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