Boosting Immunity
With Herbs

by Rob McCaleb, HRF President

For over 4,000 years, the Chinese have used certain herbs to prevent common diseases. The ancient Chinese knew nothing of bacteria or viruses, yet some of these herbs were said to "strengthen the exterior", or the "shield". Modern scientific research is confirming that they were right. Thousands of years later, and sixty years after the discovery of penicillin, the study of herbs affecting the immune system is one of the hottest topics in pharmacological research. Can herbs really strengthen our resistance and help us lead healthier lives? Both the wisdom of centuries of observation, and the scrutiny of the scientific laboratory, support the view that they can.

Our immune system recognizes and destroys anything foreign to the body, including cells like bacteria and other microbes, and foreign particles including toxic compounds. This recognition and destruction is performed by cells in the circulatory and the lymphatic systems. These cells are produced in the bone marrow and lymphatic tissue (thymus, lymph nodes, spleen and tonsils) respectively. The cells begin their lives as "stem cells". These cells are so featureless that there is no way to determine what type of blood cell they will ultimately become. They may develop into any of a number of different kind of cells, for instance: red blood cells, various types of white blood cells, etc. These cells are then released into the blood stream and are carried to all parts of the body. There are essentially two types of cells, one of which is called "memory cells". Memory cells, as the name implies, remember specific foreign cells or chemicals to which they have been exposed, and react immediately when they are next exposed to those compounds. Drugs which effect the memory cells stimulate immunity only to one disease or antigen. Vaccines are an example of drugs which effect memory cells.

Most herbs for the immune system don't affect memory cells, but are general immune system stimulators (immunostimulants). They increase the activity of the immune system but are not specific to a particular disease or "antigen" (a protein against which immune cells act). Rather, they increase resistance by mobilizing "effector cells" which act against all foreign particles, rather than just one specific type (i.e. a measles virus).

Remarkably, since the discovery of penicillin, our scientists, in search of drugs against infectious disease, have looked only for chemicals which kill bacteria or viruses. Finally, they are coming to realize that it is possible to boost the immune system, which can then fight naturally against infectious agents, without the drawbacks of antibiotic therapy. While immune stimulants cannot replace antibiotics in some cases, they have proven far superior in others.

Here are a few of the best researched immune boosters available in natural food stores:


Chinese astragalus root, Astragalus membranaceus, is widely used throughout the Orient as a tonic food and medicinal plant. In Asia, this plant is sold as dried slices of root, six to twelve inch long. Research has shown that this root and its extracts are powerful stimulators of the immune system. In Asia the roots are frequently boiled, along with other herb ingredients--and frequently some chicken broth--to produce a tonic/medicinal soup. Astragalus has been used for thousands of years in China. First mentioned in the Divine Husbandman's Classic of the Materia Medica, an ancient Chinese medicinal text, astragalus is said to "tonify the Spleen, Blood and Qi", and is used for "wasting and thirsting syndrome". Some of the specific Chinese uses hint at a stimulant effect on the immune system. For example, it used as a tonic for the lungs, for frequent colds or shortness of breath. The Chinese also use it (internally) for chronic ulcerations and other persistent external infections.

Astragalus stimulates virtually every phase of immune system activity. It increases the number of "stem cells" in the marrow and lymph tissue, and stimulates their development into active immune cells which are released into the body. Research documenting this also demonstrated that astragalus could promote or trigger immune cells from the "resting" state into heightened activity. Another study on an astragalus-based Chinese remedy demonstrated "the tendency to stimulate immune response" without suppressive effects. Long-term use (for 35 days) heightened the activity of spleen cells. The remedy also decreased negative side effects of steroid therapy on the immune system. The author recommended using it in combination with steroid therapy "to alleviate the adverse effects" of the steroid.

Perhaps the best evidence to date for the powerful immunostimulant effects of astragalus come from the University of Texas Medical Center in Houston. There, scientists tested damaged immune system cells from cancer patients, compared against cells from the blood of normal human subjects. Astragalus extracts were able to completely restore the function of cancer patients' immune cells,,,. In some cases, the compromised cells were stimulated to greater activity than those from normal human subjects. The study concluded, "a complete immune restoration can be achieved by using a fractionated extract of Astragalus membranaceus, a traditional Chinese medicinal herb found to possess immune restorative activity in vitro".

Astragalus has also been found to stimulate the production of interferon, and increase its effects in fighting disease. The combined effect of interferon and astragalus root "resulted not only in decreased common cold incidence but also in shortening the course of illness... The average course of illness of the patients in the combined treatment group was 2.6 days as compared to 4.6 days in the control group." In the same study, the astragalus root was found to increase the life span of human cells in culture. The authors report no toxicity to human cells. "On the contrary, cell counts indicated that the vital cells in cultures treated with this drug for three weeks were markedly more numerous than those without treatment". The treated cells also became resistant to a common virus and astragalus promoted regeneration of cells in the bronchi of virus-infected mice.

As if this weren't impressive enough, another study probed the activity of macrophages, one of the major cells responsible for consuming invading microbes. The activity of the macrophages was significantly enhanced within six hours of treatment, and the enhancement persisted for at least seventy-two hours. The extract also significantly inhibited the growth of tumor cells in mice, especially when combined with the extract Ligustrum lucidum (privet). The authors remark that astragalus extract "may thus restore immunocompetence; potentially beneficial for cancer patients as well as AIDS patients".

Most consumers probably use astragalus to prevent and treat colds and other minor diseases. In the Chinese research mentioned above, astragalus reduced the incidence of common colds among users, and shortened the duration of colds by almost half.


Echinacea is a very popular American wildflower and garden plant, the purple coneflower. It's also one of America's most popular herbal products, also used to prevent and treat the common cold, influenza and infections. Echinacea is the best known and one of the most researched of immunostimulants.

Echinacea was among the most popular herbs used by Native American Indians. At least 14 tribes used Echinacea for a coughs, colds, sore throats, infections, toothaches, inflammations, tonsillitis, and snake bites, among other uses. It was used by the Dakotas as a veterinary medicine for their horses.

By the early Twentieth century, echinacea had become the best selling medicinal tincture in America, used for a variety of internal and external conditions. But by 1910 it had been dismissed as worthless by the AMA, although it continued to be used. Echinacea fell into disuse in this country in the 1930's. However, Europeans began growing and using echinacea, especially the Germans, and to this day have produced the best scientific documentation of its value. The extract's popularity in the U.S. grew rapidly during the 1980s, and the plant is now again among America's best-selling herb extracts.

The most common anecdotal reports about the use of ecinacea are from people who begin taking the extract at the first sign of a cold. Often to their surprise, they find the cold has disappeared, usually within twenty-four hours, and sometimes after taking the extract only once. Anecdotal evidence carries little weight in scientific circles, but plant drug researchers have conducted over 350 scientific studies about echinacea. Here's what some of those studies say about echinacea:

The most consistently proven effect of echinacea is in stimulating phagocytosis, or the consumption of invading organisms by white blood cells and lymphocytes. To prove this, scientists incubate human white blood cells, yeast cells and echinacea extract. They examine the blood cells microscopically and a count the numbers of yeast cells gobbled up by the blood cells. Extracts of echinacea can increase phagocytosis by 20-40%. Another test, called "the carbon clearance" test, measures the speed with which injected carbon particles are removed from the bloodstream of a mouse. The quicker the mouse can remove the injected foreign particles, the more its immune system has been stimulated. In this test too, echinacea extracts excel, confirming the fact that this remarkable plant increases the activity of immune system cells so they can more quickly eliminate invading organisms and foreign particles.

As with astragalus, echinacea causes an increase in the number of immune cells, further enhancing the overall activity of the immune system. Echinacea also stimulates the production of interferon as well as other important products of the immune system, including "Tumor Necrosis Factor", which is important to the body's response against cancer.

Echinacea also inhibits an enzyme (hyaluronidase), which is secreted by bacteria, and helps them gain access to healthy cells. Research in the early 1950's showed that echinacea could completely counteract the effect of this enzyme, and this could help prevent infection when used to treat wounds. While echinacea is usually used internally for the treatment of viruses and bacteria, it is being used more externally for the treatment of wounds. It also kills yeast and slows or stops the growth of bacteria, and helps to stimulate the growth of new tissue. It combats inflammation too, further supporting its use in the treatment of wounds.

Research in 1957, showed that an extract of echinacea caused a 22% reduction in inflammation among arthritis sufferers. That is only about half as effective as steroids, but steroids have serious side-effects. Steroids also strongly suppress the immune system, which makes them a poor choice for treating any condition in which infection is likely. Echinacea, on the other hand, is non-toxic, and adds immune-stimulating properties to its anti-inflammatory effect.

Most people use echinacea for warding off colds and influenza. Extracts, either alcoholic or non-alcoholic, are the most commonly used form, and the usual amount taken is one dropperful at a time (15-25 drops). This is taken at the first sign of a cold and repeated two or three times a day. European clinics do not use continuous doses of echinacea but rather alternate three days on and three days off. This is because some testing shows that the immune system in healthy subjects can only be stimulated briefly before returning to its normal state. After several days without stimulation, immunostimulants can again be effective.

Echinacea has an excellent safety record. After hundreds of years of use, no toxicity or side-effects have been reported except rare allergic reactions in sensitive individuals. The purple coneflower is a truly American contribution to world health care through herbs. This safe and effective immune stimulant was discovered and first used by the Native Americans and is now a major medicinal plant used throughout Europe and the U.S.

The Herb Research Foundation (HRF) is dedicated to returning safe natural remedies to prominence in modern health care. We conduct, support and encourage research and educational projects in the areas of health, conservation and international development.

Astragalus References:

Bensky, D. and Gamble, A., Chinese Herbal Medicine, 1986, Eastland Press.
Rou, Ma and Ren Fu-Xie, Journal of Traditional Chinese Medicine , 1983, 3(3) pp. 199-204.
Iwama, H, et al., 1986, Planta Medica, pp. 247-50.
Mavligit, G.M. et al., 1979, J. Immunology, 123, pp. 2185-88.
Sun, Y., Cancer, 52(1), 1983, 7/3, pp. 70-3.
Chu, D., et al., Clin. Immuno. and Immunopathology, 1987, 45, pp. 48-57.
Chu, D., et al., J. Clin. Lab. Immunol., 1988, 25, 125-9.
Yunde, H., Chinese Medical Journal, 1981, 94(1), pp. 35-40.
Lau, B. et al., Phytotherapy Research, 1989, 3(4), pp. 148-53.

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