Soy compounds may protect from breast cancer

Reported by Susan Aldridge, PhD, medical journalist

A study in monkeys suggests that natural plant estrogens found in soy do not increase breast cancer markers.
Soy is rich in compounds known as phytoestrogens which mimic the effect of the female hormone estrogen. But some breast cancers grow faster in the presence of estrogen, so there has been concern over whether soy is safe from this point of view.

Researchers at Wake Forest University carried out a study in 31 postmenopausal monkeys, rotating them through eight different diets which varied as to their phytoestrogen and estrogen content. The four phytoestrogen concentrations were zero, 60 milligrams (equivalent to an Asian diet), 120 milligrams (the highest dose possible through diet alone) and 240 milligrams (diet plus supplementation). Estrogen doses were equivalent to low or high doses found in postmenopausal women.

The researchers looked for breast cancer cell proliferation and other breast cancer markers. None of the phytoestrogen levels increased the markers, although high estrogen did, as expected. The high phytoestrogen level tended to block the effects of estrogen in these experiments - suggesting that a diet high in soy might even be protective against breast cancer.

Source
Cancer Research 15th January 2006

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