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Red Clover, Soy and Other Phytoestrogens Pose No Heart or Cancer Risk


Women who have been worried about the safety of phytoestrogens like soy, red clover isoflavones, genistein, and others may breathe easier, according to a new meta-analysis of 92 trials. Researchers did not find a link between use of phytoestrogens and risk of heart problems or breast cancer, as some studies have suggested.

Phytoestrogens are chemical compounds found in plants that mimic the actions and functions of estrogen. Although they are thousands of times weaker than natural estrogen, they are present in the blood at levels thousands of times higher than natural estrogen.

The major phytoestrogen groups are isoflavones, flavones, coumestans, and lignans. Isoflavones are present in high concentrations in soybeans and soybean products, such as tofu and tempeh. A three-ounce piece of tofu, for example, contains about 23 milligrams of isoflavones. Phytoestrogens are also found in flax seed, sesame seed, multigrain breads, hummus, garlic, mung bean sprouts, black cohosh, dong quai, and red clover, among other foods and herbs.

In the current study, which was published in The American Journal of Medicine, the investigators evaluated data from 92 randomized, controlled trials, which encompassed 9,629 participants. Their analysis did not find any indications of serious adverse effects among women who took phytoestrogen treatment that included soy and red clover isoflavones and compounds such as genistein, naringenin, kaempferol, and various lignans such as enterolactone and enterodiol. Phytoestrogens are sometimes taken by women who want to avoid hormone replacement therapy but who want relief from menopausal symptoms.

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When the researchers compared the incidence of side effects between participants who took phytoestrogens with those who took placebo, they found it to be nearly the same: 36.7 percent in the phytoestrogen groups and 38 percent in the placebo groups. Side effects associated with synthetic hormone replacement therapy include an increased risk of

* blood clots
* dementia
* myocardial infarction
* stroke
* lung cancer
* ovarian cancer
* breast cancer

Most of these increased risks were discovered during the Women’s Health Initiative studies.

While the current study evaluated the safety of phytoestrogens and showed them to be a safe alternative to hormone replacement therapy, it did not address how effective they are in the treatment of menopausal symptoms. Numerous studies have been conducted that indicate how phytoestrogens can reduce symptoms such as hot flashes, cramping, and sleep disturbances associated with menopause.

Tempfer CB et al. The American Journal of Medicine 2009 Oct; 122(10): 939-46
Women’s Health Initiative studies