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Last Updated: Jun 30, 2008 - 11:14:37 AM |
Soy isoflavones may not raise markers for breast cancer in postmenopausal women and could protect them against the disease, suggests a new animal study published in the Jan. 15 issue of the journal "Cancer Research."
In the study, Charles Wood and colleagues from Wake Forest Univ. Baptist Medical Center gave eight different diets to 31 postmenopausal cynomolgus monkeys to see the effect of soy isoflavones on breast cancer risk.
The diets varied with soy isoflavones and estrogen. Isoflavones were used in different amounts: 0 mg, 60 mg (comparable to a typical Asian diet), 120 mg, and 240 mg isoflavones.
Estrogen was used at either a low or high level.
Researchers found isoflavones did not affect breast cancer markers in those receiving diets with low estrogen. Those receiving diets with zero or low isoflavones were more likely to have increased breast cell proliferation, a breast cancer marker.
For those using diets with high levels of estrogen and isoflavones, the effect of estrogen was blocked by the isoflavones.
The findings suggest that women at high risk of estrogen-dependent breast cancer may benefit from a diet rich in soy isoflavones.
Soy benefits are highly controversial. The major positive functions of soy isoflavones include relief of menopause symptoms, reduction of heart disease risk and cancer risk, prevention of prostate cancer and bone health prevention.
Adverse effects associated with consumption of large quantities of soy isoflavones observed in animal studies include reproductive effects, infertility, thyroid or liver disease.
Consumption of soy or soybean products is popular in Asian countries such as Japan and China. Chinese women are known to have a low rate of breast cancer, which is believed to be associated with dietary soy isoflavones.
The general consensus appears to be that dietary levels of isoflavones are safe and perhaps beneficial even though some adverse effects are linked with consumption of large quantities of soy isoflavones.
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