Drinking milk linked to cancer in women

September 17, 2002 in Cancer Prevention, Nutrition Topics in the News, Women's Health

Drinking milk linked to cancer in women

Drinking milk may raise blood levels of a cancer-promoting hormone in women, according to two recent studies. And taking hormone replacement therapy (HRT) or having multiple children appears to reduce levels of the hormone.

However, the researchers say it is premature to recommend that women avoid milk products, since it is not clear whether milk, or a particular component of milk, is the culprit. Similarly, more research is needed into the effects of HRT on cancer risk, since a large study recently found that taking HRT increased the risk of breast cancer.

The data on more than 1,000 women analyzed in both reports was drawn from the U.S. Nurses' Health Study, the longest national health study conducted in women. One report found that levels of insulin-like growth factor-1 (IGF-1), a hormone that can raise cancer risk when levels are too high, fell as the number of pregnancies increased. Women who had been through at least four pregnancies had IGF-1 levels that were 14% lower on average than their peers who had fewer children.

Pregnancy is known to decrease a woman's risk of breast and colon cancer, and the study--the first to report an association between the number of times a woman has given birth and IGF-1 levels--suggests a possible mechanism behind this effect.

A second study found that IGF-1 levels rose in tandem with women's intake of protein, especially from milk. There was no association between IGF-1 levels and vegetable protein intake. Yogurt, cheese and ice cream also had no association with the hormone.

Taken together, the study findings suggest a link between lifestyle factors and levels of a hormone associated with cancer risk.

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