Smart Diet Bolsters Immune System To Fend Off Gate-Crashing Germs

With every breath you take and bite of food you eat, potentially hazardous viruses and bacteria go along for the ride. But the human body doesn’t welcome these hitchhikers. It wields an arsenal of defenses—the immune system—to ward off intruders.

<font face="Arial" color=”#000000″ size=”3″>Herbs as Immune Backup

Echinacea and ginseng are the most promising immune-boosting botanicals, according to herbalist Adriane Fugh-Berman, M.D., chair of the National Women’s Health Network in Washington D.C.

<font face=”Arial” color=”#000000″ SIZE=”1″>Ginseng is thought to stimulate immune function by increasing the production of lymphocytes and interferon. An Italian study found that those who took 100 milligrams of Ginsana twice a day for 12 weeks suffered fewer colds and flu than those taking a placebo. But other findings have been conflicting. And finding good quality ginseng is a challenge. (See EN, June 1998.)

Echinacea has a better track record; it’s been shown to enhance immunity at both the cellular and blood level. (See EN next month for its effect on the common cold.) Other compounds being studied for immune-boosting properties include the spice turmeric, shiitake mushrooms and garlic.


Some factors (age, genetics) that influence how well your immune system responds to gate-crashers are out of your control. But researchers are finding that the nutrients you eat have a powerful effect on immunity. For example, vitamin A is key to maintaining the protective barriers that line the mouth, lungs and intestines and filter out marauding microbes.

How Much Is Enough? Research shows you don’t need megadoses of vitamins and minerals to maintain a well-functioning immune system. Simply meeting recommended levels for most nutrients may be enough. In fact, excesses of some nutrients, especially minerals, can be harmful. For example, excessive iron can exacerbate the infectious process as much as too little. Likewise for copper. Too much copper creates nasty free radicals in cell membranes, causing DNA damage.

Even zinc—the nutrient of the hour for fending off colds—can be too much of a good thing in large amounts. Too much zinc can deplete the body of copper, suppressing immunity.

A varied diet is the ideal way to ensure the correct balance of nutrients for optimal immune functioning. At least one study, however, has shown that a daily multivitamin/mineral can boost immune function, especially if your diet is less than optimal to start.

Can Vitamin E Keep You Flu-Free? Of all the nutrients being studied, vitamin E shows the most promise as a single supplement. A recent study of 80 healthy older people found that supplementing with E improved immunity. Volunteers supplementing with the vitamin reported fewer infections than those receiving a placebo.

Simin N. Meydani, Ph.D., of the Human Nutrition Research Center on Aging at Tufts University in Boston, found that 200 milligrams of vitamin E was the optimal amount to produce a positive immune response. Higher doses provided no further benefit.

<font face=”Arial” color=”#000000″>Glossary

<font face="Arial" color=”#000000″ SIZE=”1″>B cells— Plasma cells, which produce antibodies, and memory cells, which recognize organisms in subsequent attacks.
<font face="Arial" color=”#000000″ SIZE=”1″>Immunoglobulins— <font face="Arial" color="#000000" SIZE=”1″>Antibodies that first recognize and destroy foreign invaders.
<font face="Arial" color=”#000000″ SIZE=”1″>Lymphocytes— <font face="Arial" color="#000000" SIZE=”1″>White blood cells that include B and T cells.
<font face="Arial" color=”#000000″ SIZE=”1″>Neutrophils— <font face="Arial" color="#000000" SIZE=”1″>A type of leukocyte that combats infection by scavenging bacteria.
<font face="Arial" color=”#000000″ SIZE=”1″>T cells— <font face="Arial" color="#000000" SIZE=”1″>T helper cells, T killer cells and suppressor T cells, which directly kill pathogens or work via assistants called cytokines, including interleukin, interferon and tumor necrosis factor.
<font face="Arial" color=”#000000″ SIZE=”1″>Thymus— <font face="Arial" color="#000000" SIZE=”1″>A gland essential to the production of mature T cells.

Which Fat Fights Infection? If there is a downside to the current craze of extremely-low-fat diets, it may be impaired immune function, say some experts. Because the body cannot make them, we need to ingest small amounts of two essential fatty acids: linoleic acid (an omega-6 fat found in most vegetable oils and margarines) and alpha-linolenic acid (an omega-3 fat found in fish, uuflaxseed, walnuts and canola oil). Not getting enough of these essential fats can delay wound healing, one measure of immune function. The average American has no trouble getting omega-6’s. It’s our omega-3 intake that could use a boost.

EN Sums Up. Keeping your immune system in tip-top working order does not require Herculean efforts, or even scads of supplements. (Perhaps just a basic multivitamin/mineral and a vitamin E supplement.) A lifetime of intelligent eating undoubtedly provides the base to build on and is a logical place to start.

EN’s Blueprint for a Strong Immune System

  • Eat a wide variety of foods. Include five to nine servings of fruits and vegetables daily, plus whole grains, lean protein, nonfat dairy foods and small amounts of nuts and seeds.

  • Include fish in your diet weekly.

  • Keep fat intake below 30% of calories. Limit margarine. Go easy on corn, safflower, sunflower and soybean oils. Use olive and canola oils primarily.

  • Take a multivitamin/mineral supplement that provides 100% of the Daily Value for most nutrients, particularly B vitamins and minerals, which are harder to get from foods.

  • Consider a vitamin E supplement (200 IU of natural source mixed tocopherols or 300 to 400 IU of synthetic).

<font face=”Arial” color=”#000000″ size=”3″>Key Nutrient-Immune System Links

<font face="Arial" color="#000000" SIZE=”1″>Nutrient <font face="Arial" color="#000000" SIZE=”1″>Immune Defense Affected Getting the Right Amount
Protein Immunoglobulins Eat legumes or small servings of lean meat, chicken and fish.
Omega-6 fats Wound healing, T cells Eat corn, safflower, soybean and sunflower oils, but in small amounts only. Limit margarine.
Omega-3 fats Wound healing, inflammation Eat fish at least once a week. Eat walnuts, flaxseed oil and canola oil, in moderation.
Vitamin A and carotenoids Mucous membranes, lymphocytes Eat deep yellow, orange, red and green veggies.
B Vitamins (riboflavin, folate, B6, B12) Antibodies, leukocytes Eat dark leafy greens, bananas, legumes, whole grains, low-fat milk, lean meats. Take a multivitamin/mineral with 100% of Daily Values.
Vitamin C B cells, T cells Eat citrus fruits, tomatoes, strawberries, broccoli, cauliflower and dark leafy greens.
Vitamin E Antibodies, antioxidants Take 200 IU of natural-source vitamin E (or 300-400 IU synthetic E).
Copper T cells, neutrophils Eat beans, whole grains, apricots and potatoes. Take a daily multivitamin/mineral.
Iron Lymphocytes Eat small amounts of lean meats or take a daily multivitamin/mineral (limited to 10 milligrams of iron if post-menopausal or male).
Zinc Thymus, T cells Eat beans, wheat germ, whole grains, lean beef and turkey. Take a daily multivitamin/mineral.

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