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By Frances Albrecht, M.S., C.N.

Boosting your body's immunity against disease may be as simple as ensuring adequate zinc intake. Zinc is considered one of the most critical micronutrients because it's crucial to preserving a healthy immune system. Yet, many studies show that three-quarters of all American adults lack sufficient dietary zinc and that many consume only 8 to 10 mg. per day, about two-thirds of the Recommended Daily Allowance (RDA) of 15 mg. per day (Journal of the American Medical Association, 1979, vol. 241). 

    Marginal zinc deficiency is common in the United States due to soil exhaustion (soil that's depleted of minerals), food processing, poor cooking methods and inadequate intake of naturally zinc-rich foods including oysters and other shellfish, lean meats, dark poultry meats, eggs, dairy products, whole wheat and other grain foods, pumpkin and sunflower seeds, and brewer's yeast.

    Americans most at risk for zinc deficiencies are the elderly, vegetarians who don't get adequate intake from nonmeat sources, those on low-calorie diets, pregnant women and people living with HIV.

    Zinc has many roles in the body. It's part of 70 or more metallo-enzymes (enzymes that require a metal such as zinc or copper to be active), many of which decrease in activity during zinc depletion. It stimulates production of gamma interferon, a cancer- and disease-fighting substance essential for immune strength. Zinc is also required for DNA and protein synthesis and is considered one of the most critical nutrients for the immune system due to its stimulating effect on T-cell maturation. T-cells are the immune system's primary disease fighters, and they also direct the work of the B-cells, which make antibodies.

    Without adequate zinc, the thymus gland, which oversees the workings of the immune system including the maturation of T-cells, becomes less active, resulting in decreased immune function. At birth the thymus gland, located behind the top of the breastbone, is about the same size as the heart. Over a lifetime, the thymus shrinks until it's no longer visible by x-ray. Not long ago, shrinkage of the thymus gland, along with concomitant age-related impairment in immune function, was believed to be an inevitable and irreversible part of aging. Now researchers have shown that decrease in thymus size and activity is preventable in part with adequate zinc intake and that decreased immune function is reversible upon adequate administration and absorption of zinc (Nutrition Reviews, 1983, vol. 41).

    For people deficient in this mineral, zinc therapy has been shown to improve immune function, promote wound keeling and aid skin conditions such as acne, eczema and psoriasis. Zinc is necessary for the absorption of linoleic acid, a fatty acid necessary for healthy skin.

    One of the most compelling reports detailing the effects of zinc deficiency was released in 1961 by researchers who described the deficiency symptoms of eleven 20-year-old Iranian males with symptoms of dwarfism, infantile sex organs and lack of mental acuity. Subsequent controlled studies using zinc resulted in a dramatic increase in the onset of sexual maturation and growth rate (Current Topics in Nutrition and Disease, 1988, vol. 18).

    Other symptoms associated with zinc deficiency include alteration in taste perception, menstrual irregularities, lack of appetite and hair loss. The appearance of white spots or bands in the fingernails may also be signs of zinc deficiency.

Treating the Common Cold

Zinc is especially helpful for those battling the common cold. In one double-blind study, use of zinc gluconate lozenges by subjects suffering from cold symptoms significantly reduced the average duration of the common cold. After one week, 86 percent of 37 subjects using the zinc lozenges were without cold symptoms versus 46 percent of the 28 placebo-treated subjects (Antimicrobial Agents and Chemotherapy, 1984, vol. 20).

    Aside from combating the rhinovirus the most common cause of the common cold, zinc has also been shown to inhibit the growth of several other viruses including Herpes simplex (Antimicrobial Agents and Chemotherapy, 1981, vol. 19).

    People living with HIV are commonly found to be deficient in zinc due to inadequate dietary intake; alterations in metabolism, increased rate of infections and malabsorption problems. Supplementation with zinc is particularly important for those with HIV, as research has shown a concomitant rise in HlV-related diseases with decreasing zinc stores (Journal of Internal Medicine, 1992, vol. 231).

    Zinc absorption is enhanced by soy protein, glucose, lactose and red wine. Absorption is inhibited by excessive copper or iron and stress. Conversely, excess zinc intake can impair copper absorption; when supplementing long-term with zinc, make sure to get about 1 mg. of copper per 10 mgs. of zinc.

Frances Albrecht is president of Nutrition Education Services and is a Distance Learning Instructor at Bastyr University. She lives in Seattle, Wash. Visit Bastyr's Web site at http.//www.bastyr.edu.

This story is produced through the Bastyr University Health Information Project, funded by INDENA, U.S.A., raw material suppliers of standardized herbal extracts. Bastyr University offers a program in naturopathic medicine (N.D.); bachelor's degrees in the natural health sciences; and master's degree programs in nutrition, acupuncture and Oriental medicine. For information, contact Bastyr University, 14500 Juanita Drive NE, Bothell, WA 98011; 206-823-1300.