Influence of menopause on cancer risk
Menopause is often linked with an increased risk of cancer, because post-menopausal women are more likely to develop cancer than pre-menopausal women. But aging is more likely to be the cause of this increased risk. The age when the woman reaches menopause may have an effect on cancer risk. Uterine and breast cancers are affected by the lifetime exposure to estrogen. Because estrogen level drops after menopause the lifetime exposure to estrogen is lower in women who experience menopause early in their live. Not only does an early menopause reduce the risk of uterine and breast cancer, but it also lowers the risk of ovarian cancer, which is directly link to the number of ovulations.
Hormone replacement therapy
Hormone replacement therapy is still often used as a treatment for relieving menopause symptoms
such as hot flashes and vaginal dryness, as well as reducing the risk of osteoporosis and atherosclerosis. But this therapy increases the risk of breast cancer. On the other hand, pre-menopausal women with breast cancer who are treated with tamoxifen may experience an early menopause.
Isoflavones and cancer risk
Does the intake of isoflavones increases cancer risk in women? Because isoflavones are structurally similar to estrogen many have theorized that they may increase breast and uterine cancer risk. Even many doctors recommend women to be reduce the intake of soy or isoflavones, under the motto "better be safe than sorry". Scientific evidence is often conflicting but most studies show that isoflavones do not increase cancer risk, some studies even demonstrate a beneficial effect. One study concluded that isoflavones exposure at levels consistent with historical Asian soyfood intake does not result in adverse stimulatory effects on breast tissue (1), whereas another prospective study suggested that approximately 10 mg of isoflavones per day, obtained in a standard serving of tofu, may have lasting beneficial effects against breast cancer development (2).
(1) Soy isoflavones, estrogen therapy, and breast cancer risk: analysis and commentary. Nutr J. 2008 Jun 3;7:17.
(2) Soy intake and breast cancer risk in Singapore Chinese Health Study. Br J Cancer. 2008 Jul 8;99(1):196-200.