Can herbs help fight cancer?
As many as 88 percent of all cancer patients seek help from herbs and other alternative therapies. It's easy to see why. Certain herbal remedies appear to work -- after all, the potent anticancer drug taxol comes from the bark of the yew tree -- and compared with nauseating, painful, expensive, and sometimes ineffective conventional treatments, taking herbs or drinking medicinal teas may seem like an attractive option.
But remember that the Food and Drug Administration doesn't require testing for herbs and supplements as it does for conventional drugs, so it always pays to be cautious in the largely unregulated world of herbal medicines. Although some are clearly of value, other so-called cancer remedies are worthless, dangerous, or both. Always check with your doctor before trying a new herb, and consult people who have used it, if possible, to get some idea of what you're getting into.
Here's a look at what's known about the potential strengths, weaknesses, and side effects of some of the most popular herbal treatments for cancer.
This herb, also known as Huang ch'i, may help fight cancer by stimulating the immune system. When researchers at the University of Texas Medical Center mixed astragalus with the blood of cancer patients in a test tube, the function of cancer-killing cells called T lymphocytes improved by 260 percent. However, the American Cancer Society says there is no convincing scientific evidence that astragalus helps to fight cancer or mitigate the effects of chemotherapy.
The downside is that the herb can cause low blood pressure, dizziness, and fatigue, and overdoses can damage the immune system. When used orally in appropriate dosages, usually 9 to 30 grams a day, astragalus seems to be safe, according to the Natural Medicines Comprehensive Database.
Once touted as a safe, effective herbal treatment for prostate cancer, PC-SPES is actually serious medicine with equally serious side effects. Researchers from Robert Wood Johnson Medical School found that the herbal cocktail -- a combination of eight traditional Chinese herbs including saw palmetto, skullcap, licorice, and Panax pseudo-ginseng -- dramatically increased estrogen levels and decreased testosterone in eight cancer patients. This hormonal shift has the potential to slow the growth of prostate cancer (which is why many prostate cancer patients take estrogen), but it comes with a price. All eight patients reported breast tenderness and a loss of sex drive, and one patient developed a blood clot in his leg.
And while PC-SPES has been proven to shrink prostate tumors, it was taken off the market in February 2002 after it was found to contain traces of the prescription drug warfarin (a blood thinner). Because the PC-SPES was tainted with prescription drugs, it is unknown whether it was the PC-SPES, the prescription drugs, or a combination of the two that led to the results. Subsequent tests have found additional traces of strong drugs in PC-SPES, including an artificial form of estrogen and a pain reliever called indomethacin that may act against tumor cells. The National Center for Complementary and Alternative Medicine (NCCAM) plans to conduct new clinical trials of PC-SPES once it can guarantee a standard product.
Known by the scientific name of Uncaria tomentosa, this South American vine is an ancient treatment for arthritis, cancer, and other diseases. Cat's Claw remains popular among cancer patients despite the fact that the National Cancer Institute decided that the active ingredients in the herb weren't powerful enough to justify further studies. The herb is generally safe -- as long as you get the right kind. There are more than 30 plants that go by the name Cat's Claw, and some that are not Uncaria tomentosa end up in herbal remedies. They can cause gastric bleeding and other side effects, and won't deliver the mild benefits patients are seeking.
This herbal tea (a blend of Indian rhubarb, sheepshead sorrel, slippery elm, and burdock root) has been promoted as a cure for all cancers, but there's little evidence that it has any curative powers. Studies at both Memorial Sloan-Kettering and the National Cancer Institute found that the tea failed to slow the growth of tumors in lab animals. Furthermore, a Canadian study of 77 cancer patients taking the herbal treatment found that only eight improved or remained stable. The tea, when pure, causes few side effects except for occasional nausea, but it has been known to be contaminated with the poisonous belladonna root (which closely resembles burdock root). If you do buy Essiac, stick with a well-known supplier.
Purported to prevent certain cancers, green tea may also help slow the spread of the disease. Test-tube studies at Rutgers University found that compounds from green tea slowed the division of cancer cells from the lung and colon. Other studies have found that green tea stunts the growth of tumors in mice. But the results in human studies are contradictory. The National Cancer Institute notes that some studies suggest that green tea may be an effective cancer-fighter, while other studies found no benefit. The NCI is continuing to study what effect, if any, green tea has on cancer. In the meantime, drinking a few cups of the antioxidant-rich brew each day certainly won't do any harm, but don't overdo it -- some study subjects on high doses of green tea suffered nausea and diarrhea.
This extract from European mistletoe contains compounds called lectins which, at least in theory, can kill cancer cells. A review in the journal Phytomedicine reported that Iscador improved the survival of cancer patients in 10 out of 11 trials (although the best-designed study was the one that found no effect). In addition, a Swiss study showed that Iscador more than doubled the rate of DNA repair in 12 out of 14 breast cancer patients. Other studies have shown no benefit. In a 2004 randomized trial of melanoma patients spanning eight years, researchers found no increase in survival time between those who took Iscador and those who underwent interferon treatment. And according to the Journal of the American Dietetic Association, there is a serious risk of poisoning associated with Iscador, and it shouldn't be taken without a doctor's supervision.
This compound from the pits of apricots, peaches, and plums has not proven effective; taken orally, it sometimes proves to be more poisonous than conventional cancer treatments. In a multicenter study of 170 cancer patients, every subject showed tumor progression seven months after starting laetrile therapy. What's more, the compound can cause cyanide poisoning, especially when taken orally. Still commonly dispensed in Mexican cancer clinics, laetrile is illegal in most states and is not approved by the FDA for use in the United States.
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BotanicLab Pursues Investigation of "Compound" Found In PC SPES, Business Wire, Feb. 20, 2002.
Maggie Fox. Herbal prostate pills contain drugs. September 3, 2002. Reuters Limited.
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National Cancer Institute. Complementary and Alternative Medicine in Cancer Treatment: Questions and Answers. July 2004.
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National Cancer Institute. PC-SPPES Overview. May 2010.