The pharaohs considered them plants of immorality, the Aztecs believed them sacred, and the ancient Chinese reserved them for their emperors. Today science has discovered that mushrooms contain beta glucans and other polysaccharides to strengthen the immune system. Three important species are readily available as supplements (and two make tasty treats).

1 Maitake (Grifola frondosa) is a premier culinary and medicinal mushroom. While not as well known in this country, maitake is highly esteemed in the Far East, where it’s often used on a daily basis to balance bodily functions and protect against disease. “Maitake is increasingly being recognized as a potent source of polysaccharide compounds with dramatic health-promoting potential,” says Gabriel Cousens, MD. These mushrooms “have shown particular promise as immunomodulating agents and as an adjunct to cancer and HIV therapy. They may also provide some benefit in the treatment of hyperlipidemia, hypertension, and hepatitis.” Integrative physician Andrew Weil, MD, says maitake may be the most effective immune support of all mushrooms.

Recent research has focused on maitake extracts. For example, one such maitake fraction inhibits tumor cell adhesion of vascular endothelial cells in the lungs.

A specific glycoprotein extract, known as SX-fraction, improves glucose tolerance, making it an alternative approach to improving insulin sensitivity (a growing concern for overweight and obese Americans). Studies with animals and humans suggest that maitake SX-fraction helps ameliorate the symptoms of diabetes.

Clinical research with maitake D-fraction reports benefits for people with brain, breast, liver, lung, and prostate cancers. “The use of maitake D-fraction and maitake crude powder should be characterized as immunotherapy and as a complement to chemotherapy, radiotherapy, or surgery,” write Harry Preuss, MD, and Sensuke Konno, PhD. “Its use is completely safe,” they say.

2 Reishi (Ganoderma lucidum) is a legendary mushroom dating back 2,000 years. Traditionally Taoist monks used it “to promote a centered calmness, improve meditative practices, and attain a long and healthy life,” says herbalist Roy Upton. Because of its widespread use as a tonic herb, “modern Chinese physicians readily employ reishi mushrooms to support immune resistance in patients undergoing conventional chemotherapy and/or radiation treatment for various forms of cancer.”

Newer research finds reishi may protect against bladder cancer cell growth and possibly suppress invasive breast cancer cells. It works as an immunomodulator to stimulate cytokines, macrophages, and T cells. An antiviral agent, this mushroom may also be useful in herpes and HIV infections. “In the United States, reishi mushroom is most often recommended for its immune-supporting effects,” Upton says.

Human clinical trials suggest that this medicinal mushroom also inhibits platelet aggregation, making it useful in cardiovascular disease. “A number of studies have focused on the ability of reishi to protect the liver from chemical damage and enhance its detoxifying activity,” he adds. Korean research suggests this mushroom even has “radioprotective ability,” guarding against DNA damage from ultraviolet radiation. Reishi also has shown “marked positive effects on sleep and mental well-being,” Upton notes.

Reishi is among the safest of herbs—with no side effects reported in clinical literature. However, its extracts may contain allergens, so anyone with sensitivities to fungi and mushrooms should use it carefully

3 Shiitake (Lentinula edodes or Lentinus edodes) is another gourmet mushroom with potent health benefits. The Japanese first discovered its cancer-fighting powers when scientists began to investigate why people living in two remote mountainous regions had such low rates of this disease: The answer was eating lots of shiitakes. In vitro studies show that this mushroom inhibits proliferation of breast cancer cells, and other research suggests that it works via multiple pathways to fight cancer, diabetes, and high cholesterol. A natural antibiotic active against bacteria, fungi, and yeasts, shiitake helps prevent colds and appears to rein in the blood-vessel overgrowth implicated in macular degeneration.

Lentinan extracted from these mushrooms may stimulate the capacity of specialized blood cells to produce immune-supporting interleukin and tumor necrosis factor, which is how it may prevent the growth and spread of cancer. This extract is particularly useful when surgery is feasible for those with advanced stomach cancer, and lentinan has also increased survival time for lung cancer patients.

Another shiitake extract, active hexose correlated compound (AHCC) is an immune-enhancing supplement and adjunctive treatment for liver cancer. A Phase I trial finds it safe with only minimal side effects (bloating, diarrhea, fatigue, foot cramps, headache, and nausea) in 20 percent of patients tested.

While shiitake is very safe, it may cause temporary abdominal bloating and diarrhea in high doses. Anyone with bladder cancer should avoid raw shiitake, which contains a substance linked to that disease.