Soy isoflavones and breast cancer/puberty timing
By Jimmy Downs
Saturday Oct 6, 2012 (foodconsumer.org) -- A new review in Revista Medica de Chile suggests that eating soy food or taking soy isoflavones supplements at a right time may help prevent breast cancer.
L. Valladares of Universidad de Chile in Santiago, Chile and colleagues conducted the review and found associations between intake of soy isoflavones and risk of breast cancer at women's different physiological phases.
Soy isoflavones, dietary or supplemental, reduces risk of breast cancer, according to epidemiological studies, by competing with estrogen for estrogen receptors, which are involved in the development of hormone positive tumors.
Estrogen, a female sex hormone, is known to be a breast cancer promoter. A woman who has a longer exposure period are at a higher risk for the cancer, compared with those who have a shorter period of exposure. High levels of estrogen can also be a risk factor.
Because of the role estrogen plays in the development of breast cancer, early puberty, late menopause and hormone replacement therapy can increase risk for breast cancer where late puberty can reduce the risk.
The authors say that epidemiological studies have shown consumption of isoflavones was associated with lower incidence of breast cancer. However, human intervention studies have shown soy isoflavones can have either a promoting and inhibiting effect on breast cancer in pre- and postmenopausal women.
When soy isoflavones are used at the time an individual has a higher level of estrogen like in premenopausal women, particularly at very young ages, soy isoflavones, which have a weaker estrogenic activity compared to estrogen, can function as antagonists for estrogen receptors to reduce the risk of breast cancer.
When soy isoflavones are used at the time an individual has a lower level of estrogen like in postmenopausal women, soy isoflavones can act as agonists for the estrogen receptors to boost estroegnic effects on breast cancer development.
Intake of soy isoflavones prior to puberty can lower serum levels of estrogen and delay onset of puberty, which will reduce a woman's cumulative exposure to estrogen in their lifetime and the risk of breast cancer.
According to a scientist who once worked at Harvard, phytoestrogenic compounds or environmental pollutants that are estrogenic have much weaker estrogenic activity, compared to synthetic or natural estrogen.
Breast cancer is expected in more than 230,000 women in the United States in 2012 and the disease and its complications are expected to kill about 37,000 women in the the same year and the same country, according to the National Cancer Institute.
Breast cancer can be prevented in many cases. Two major risk factors according to an authoritative organization include hormone replacement therapy and medical radiation used in medical diagnostics and cancer treatment.
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