Defend Your Immune System

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Use echinacea to treat colds and flus.
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American ginseng can help protect you from respiratory viruses.
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Illustration by Joel Nakamura

If you were living in a cave during prehistoric times, or perhaps in a medieval hut or a trench during World War I, what would be your greatest fear? Other than attacks from predators or warring humans, bacterial infection in all its various faces would fill you with the most dread. Will that cut on my foot fester? Will this water make me sick? What if these rats actually do carry the plague?

Because the menu of dreaded diseases has changed over time, those of us who lie awake in the middle of the night these days might be worrying, not about gangrene, but about the equally frightening bogeymen of cancer, influenza, SARS, HIV or West Nile virus.

What hasn’t changed since the dawn of time is our greatest defender against all these foes: our immune system. When functioning properly, it kills bacteria, viruses, fungi and parasites. It hunts for and destroys cancerous cells or those infected with a virus. To do this work, our amazing immune system produces several types of cells (phagocytes, T-lymphocytes and B-lymphocytes), antibodies and chemicals — all without assistance from us. However, several factors under our control — diet, sleep, exercise, reducing stress levels and choosing natural supplements — can assist the immune system’s performance.

The Stress Link

Whether physical or psychological, stress raises the level of an adrenal hormone called cortisol. Cortisol plays an important function in regulating blood sugar, energy production, inflammation and the immune system. But too much cortisol over the long run can wreak havoc on the immune system and other bodily systems. A study published in Psychosomatic Medicine in 2004 found that people who felt overwhelmed and otherwise psychologically stressed actually produced fewer antibodies in response to an influenza vaccine.

Fortunately, we can modify some of the things — exercise, sleep, smoking, diet — that add to our stress load. For instance, people who exercise regularly are less prone to developing infections and cancer. Strangely, some studies show that exercise enhances immune function, while others suggest it undermines such function.

I asked Roy Shephard, M.D., Ph.D., professor emeritus of applied physiology at the University of Toronto and author of Physical Activity, Training and the Immune Response (Cooper Publications, 1997), to clarify the issue. He answered, “There is some evidence that reasonable amounts of training enhance immune function, but extreme training [which decreases the testosterone/cortisol ratio] depresses both NK cell function and the secretion of immunoglobulins.” (NK, or natural killer, cells destroy other cells that have become cancerous or infected with viruses; immunoglobulin is another word for antibody.) According to Shephard, these immune factors decrease in the blood because exercise stimulates their migration into the tissues.

Bottom line: Exercise, but don’t overdo it. The average American has no need to fear they’re getting too much exercise; most don’t get nearly enough. Even as much as an hour of exercise daily should not pose problems.

Sleep deprivation raises blood levels of cortisol and increases sympathetic nervous system activity, rendering a person jittery and hyper-aroused, making it even harder to get to sleep the next night. The prescription here is to avoid over-scheduling so you can curl up in a warm bed in a dark, quiet room at about the same reasonable hour each evening.

Smoking impairs several aspects of immune function. For one thing, it paralyzes the whip-like hairs called cilia that line the nose. Normally, these cilia are the transportation system for mucous, which lines the nasal passages and, like flypaper, traps microbes and pollutants away from the lungs. In one 2002 study, researchers used condensed cigarette smoke to suppress lung cells’ ability to fight bacterial infection, then partially reversed this effect with a potent antioxidant from green tea called epigallocatechin gallate. This doesn’t mean you can get away with smoking a cigarette if you chase it with a cup of green tea, so don’t go there!

The Nutrition Connection

Eating a well-balanced diet and maintaining a normal weight are good for your immune system. Having an eating disorder, whether it’s overeating, anorexia or bulimia, has been linked with impaired immune function. A note of caution: If you’re overweight, it’s not a good idea to go on a radically limited diet to fight flab. You’ll be robbing your body of immune-friendly nutrients, plus rapid weight loss stresses the body and suppresses immunity. One recent study, published in the Journal of the American Dietetic Association, found that women who frequently and intentionally lost weight (10 or more pounds) had lower measures of immune function.

Malnourished people typically have immune dysfunctions due to a deficiency of several key nutrients. Protein is one of them, but most Americans consume plenty of that. Other nutrients include vitamins A, C, E and several of the Bs, and the minerals selenium and zinc. Although a deficiency undermines immunity, it’s far from clear whether supplements benefit generally healthy people who eat a well-balanced diet.

You’re likely to get all your immune system requires from food, provided you avoid processed foods and go for a whole-foods diet replete with grains, colorful fruits and vegetables, and some seafood, poultry or other meats.

If your immune system is suppressed or compromised for some reason, it may make sense for you to take supplements. For instance, one study of runners showed that an antioxidant supplement (18 mg beta-carotene, 900 mg vitamin C and 90 mg vitamin E) offset the impairment in the activity of neutrophils (a type of immune cell) seen after prolonged running. In another study, published in the July 1, 2004, issue of The New England Journal of Medicine, researchers gave more than 1,000 HIV-infected pregnant Tanzanian women vitamin A, multivitamins or both. Compared to a placebo, the multivitamin regimen, plus or minus vitamin A, slowed the disease progression, maintained higher counts of CD4+ cells (also known as helper T cells, which tend to decline with HIV infection), and reduced blood levels of the virus. Vitamin A alone was less effective. Keep in mind that these women likely had deficiencies in some of these vitamins.

Suggested Supplements

Vitamin A and carotenoids are both immune friendly. Vitamin A comes primarily from animal sources (liver, kidney, butter, whole milk and fortified reduced-fat milk). The carotenoids are antioxidant plant pigments that contribute to the yellow and orange colors in fruits and vegetables. The body can convert some carotenoids to vitamin A. Others, such as lutein and lycopene, are not converted to vitamin A but have been shown to promote immune response, according to research published in 2004 in The Journal of Nutrition.

A recent study found that, compared to healthy children, kids with infections had lower blood levels of vitamin A and some carotenoids. Whether this depletion was due to decreased synthesis or increased utilization isn’t yet known. Nevertheless, it makes sense to eat plenty of carotenoid-rich foods, such as dark-green leafy vegetables, carrots, sweet potatoes, yams, squash, red peppers, tomatoes, apricots and cantaloupes.

Although vitamin C supports immune function, investigations into whether vitamin C supplements actually reduce colds and other ailments have yielded mixed results. One research paper from the International Journal of Sports Medicine reported that vitamin C supplementation (600 to 1,000 mg daily) may benefit people doing heavy exercise who experience frequent upper respiratory infections.

You either can take a vitamin C supplement (200 to 500 mg a day for prevention, 500 mg every two hours while awake if you have an infection) or consume fresh C-rich foods, such as guavas, strawberries, papayas, citrus, berries, red cabbage and peppers.

Zinc is critical to immune function and also is essential for children’s growth and development. Deficiency impairs immune function and erodes resistance to infection. Christa Walker, M.H.S., and Robert Black, M.D., Ph.D., chair of the International Health Department at Johns Hopkins University, recently reviewed the research on the influence of zinc on infectious illnesses. In zinc-deficient people, supplements can reduce the risk of infectious diarrhea and pneumonia. In one study, zinc supplementation decreased child mortality by more than 50 percent. In another, the infants of pregnant women who took zinc had fewer infections. Results on the ability of zinc lozenges or nasal gels to reduce the common cold have been inconclusive. Walker points out that, aside from the common cold studies, most of the research has taken place in developing countries, where zinc deficiency is more prevalent than in the United States.

Walker says a balanced diet usually provides adequate zinc. Oysters are particularly rich in this mineral. Other sources include other types of shellfish, fish, meat, whole wheat, pumpkin seeds, nuts and legumes. If your diet is low in such foods, you can take a zinc-containing multivitamin/mineral formula. Be aware that prolonged intake of high amounts of zinc (150 milligrams or more daily) actually can depress immune function.

The Best Botanical Immune Boosters

If you’re the type of person who catches every bug that’s going around, herbal supplements may help. Fortunately, these botanicals are generally safe and nontoxic, and therefore suitable for long-term usage.

When immunity is an issue, many people turn first to echinacea (Echinacea spp.). But if you’re looking for long-term immune support to prevent infections and fend off cancer, echinacea is not the herb of choice, according to Steven Foster, author of 14 books, including Echinacea: Nature’s Immune Enhancer (Healing Arts Press, 1991). Research supports the use of root tinctures or the fresh-expressed juice of the herb for the treatment but not the prevention of colds and flus.

At the first sniffle, you can start taking echinacea. The total daily dose is 6 to 9 ml (1 to 2 teaspoons) of fresh-expressed juice of the above-ground parts or 3 to 5 ml of root tincture (3 to 5 droppersful or 1/2 to 1 teaspoon). The first two days of symptoms, divide the total into six doses; thereafter into three to four doses. Don Brown, N.D., author of Herbal Prescriptions for Health & Healing (Lotus Press, 2000) recommends taking the herb for seven to 10 days. “According to recent studies,” Brown says, “longer treatment may not work, but is not dangerous.”

If you’re allergic to plants in the aster tribe (ragweed, asters, chrysanthemums, yarrow, arnica and chamomile), you also may be allergic to echinacea. The German Commission E recommends that people with multiple sclerosis, tuberculosis, lupus, HIV infection, AIDS or other immune system disorders avoid this herb. This advice is based upon the theory, not on actual evidence, that echinacea might stimulate T-lymphocytes (immune cells).

Although goldenseal (Hydrastis canadensis) is often included in herbal cold and flu formulas, it is not an immune-enhancing herb. It is anti-inflammatory, antiseptic and capable of killing some bacteria, fungi and parasites. Most of the research is focused on the ability of the herb to fight gastrointestinal infections.

Try a Tonic Herb

Herbal immune tonics can safely be taken long-term to gently boost the immune system. Tonics, by definition, are meant to be taken over a longer period of time to strengthen bodily systems — in this case, the immune system. Most of the immune botanicals and their attendant research come from Asia. Most of these herbs are adaptogens, substances that act in nonspecific ways to increase the body’s resistance to stress and balance various body systems. Foster points out that these herbs are used in Traditional Chinese Medicine (TCM), which employs combination formulas rather than single herbs to balance body systems.

Foster’s first choice for long-term immune enhancement is astragalus (Astragalus membranaceus). TCM practitioners use the root of this herb to build resistance to infection and enhance immunity in the elderly and others with compromised immunity. Astragalus stimulates the immune system in several ways. It promotes the development and activity of lymphocytes, macrophages and natural killer cells, as well as the production of immune chemicals such as interferon (which has antiviral and anti-tumor activity) and interleukins (which activate T-lymphocytes).

Much of the human research has been in people with cancer. Injections of herbal extracts can offset the immunosuppressive effects of chemotherapy drugs, decrease toxic drug effects and enhance the tumor-fighting effects of the drugs. In one study, published in the Journal of Immunology, a water extraction of astragalus restored or enhanced T-lymphocyte function in people with cancer. This herb also may boost the anti-tumor effect of some chemotherapeutic agents, creating the potential to reduce the dosage of these drugs (and hence, the drugs’ notorious side effects). In people whose immune systems were suppressed due to kidney dialysis, astragalus injections helped their bodies regain their immune responses.

Astragalus is safe and nontoxic. Foster prefers to take the herb as a tincture for at least 30 days. The usual dosage is 2 to 4 ml (2 to 4 droppersful) of tincture diluted in liquid three times daily. You also can decoct the chopped or powdered root into tea (1 teaspoon per cup of water) and drink 1/2 cup three times a day; or you can use the root in soup stocks (about four or five pieces of sliced root in a half-gallon pot).

For 5,000 years, Asian peoples have revered ginseng as a longevity tonic. Although several species are used, Asian ginseng (Panax ginseng) is the most widely known. Native Americans made similar use of American ginseng (Panax quinquefolius). These two species of ginseng differ somewhat in the concentrations of active ingredients, a group of compounds known as ginsenosides. Ginseng root may help promote a vigorous old age because it enhances immune function.

The immune research, which has focused on Asian ginseng, shows that this herb speeds the development and activity of white blood cells, stimulates natural killer cell activity, increases CD4+ cells and raises the body’s production of interferons and interleukins. In a group of HIV-infected people, ginseng increased CD4+ cells and other immune markers.

Two clinical trials suggest that ginseng used as a preventive can ward off respiratory infections. In one study published in 1996 in Drugs Under Experimental and Clinical Research, giving ginseng along with a flu vaccine caused a greater rise in antibody levels and natural killer cell activity and a lower incidence of cold or flu than among those who took a placebo. A recent study on American ginseng, published in the Journal of the American Geriatrics Society, found that, compared to those swallowing a placebo, seniors taking a ginseng extract were less likely to contract two respiratory viruses (influenza and respiratory syncytial virus).

Ginseng can be taken as a tea, fluid extract or dry extract. Brown recommends 100 mg once or twice daily of products standardized to supply 5 to 7 percent ginsenosides, the compounds thought to be the prime active ingredients. He says ginseng is traditionally taken for two to three weeks followed by a one- to two-week break before resuming.

When consumed within recommended guidelines, ginseng is generally safe. The herb has been reported to cause overstimulation, insomnia and stomach upset, primarily when taken in excess and/or combined with stimulants such as caffeine. If you take the blood-thinning drug warfarin (Coumadin), you should know that one British Journal of Clinical Pharmacology study found that Asian ginseng did not interact with the drug, while another (from the Annals of Internal Medicine) showed that American ginseng reduced blood levels of the drug. Brown recommends that pregnant and nursing women avoid ginseng and that people with high blood pressure first consult with their health-care practitioner.

Eleuthero (Eleutherococcus senticosus) is another TCM herb Foster turns to for long-term immune support. Although the Chinese have used eleuthero for more than 2,000 years, Russian researchers popularized the herb in studies showing that it acts as an adaptogen, hence the common name Siberian ginseng. Root extracts of eleuthero increase antibody production and the number and activity of immune cells.

The daily dose is typically 8 to 10 ml a day of an alcohol extract, 2 to 8 g of powdered root or 300 to 400 mg of a solid standardized extract. This total dose can be divided into two to three smaller doses. According to Brown, eleuthero is usually taken continuously for six to eight weeks followed by a one- to two-week break. After the break, the dose can be resumed.

Medicinal mushrooms. More than 50 mushroom species have medicinal properties. Three of the better-known species, shiitake (Lentinula edodes), maitake (Grifola frondosa) and reishi (Ganoderma lucidum), possess immune-boosting substances called polysaccharides.

Shiitake augments the production of chemicals that activate T-lymphocytes, has anti-tumor activity and increases resistance to infection with some bacteria, viruses and parasites. In mice, extracts increased resistance to infection by influenza virus. In people with cancer, lentinan (an active ingredient in shiitake) has been shown to improve immunity and prolong survival, according to research published in Anticancer Research.

The fresh mushroom is delicious sautéed. You can eat two to four a day. The dried mushroom can be taken in tea or soup. Christopher Hobbs, L.Ac., author of Herbal Remedies for Dummies (IDG, 1999) and other books, says that, in order to get a therapeutic effect for a serious illness, you need to take a concentrated extract. Follow package directions.

While lab research (such as a 2004 Current Medicinal Chemistry study) backs reishi’s immune-enhancing ability, human trials are sparse. A 2003 clinical trial found that a reishi extract improved immune function in people with advanced-stage cancer. You can take reishi dried, powdered or in teas, capsules, extracts, tinctures and syrups. Hobbs says any of the following preparations can be consumed three times a day: 1 cup of tea, 2 to 4 droppersful of tincture or 1 gram of the powdered, encapsulated mushroom. Side effects are rare, Hobbs notes, but can include upset stomach, dry throat, nosebleed and skin rash.

In Japanese, mai take means “dancing mushroom,” and the immune-enhancing power of maitake is enough to make a person dance with joy. Research has focused on the ability of a polysaccharide called the “D-fraction” to boost immune function (particularly natural killer cells) to retard the progression and spread of tumors and to counter the immune-suppressive effects of chemotherapy. Preliminary research provides hope that a different polysaccharide fraction (the MD-fraction) can benefit people infected with HIV both by stimulating immune defenses and by directly inhibiting the virus.

Scientists have yet to work out optimum dosages for maitake. Traditionally, this mushroom is consumed as a tea, in soups or in capsules. If you take a standardized extract, follow dosage instructions on package.

Treat Yourself Well

If your immune system shows signs of wearing thin, consider adding one of the immune tonics mentioned above to your regimen. If serious or frequent infection becomes a problem, be sure to consult your health practitioner. Also make appointments to see him or her regularly to screen for common cancers so they can be treated in their earliest stages.

Your immune system has worked diligently and quietly for years. Think of it as a war horse. Treat it well; armor it for those daily battles against marauding microbes and mutant cells. Eat wisely, exercise regularly, get enough sleep and avoid falling into an anxiety-filled, stressed-out lifestyle.

Linda B. White, M.D., is the coauthor of The Herbal Drugstore (see Bookshelf, Page 55) and an adjunct faculty member in the health professions department at Metropolitan State College in Denver.

The reference list for this article is extensive. If you would like a copy, please send a self-addressed, stamped envelope to “Immunity,” Herbs for Health, 1503 SW 42nd St., Topeka, KS 66609; or e-mail us at

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