Milk and Human Health

Prostate cancer

The best evidence linking prostate cancer to milk consumption appears to be that for aggressive and fatal prostate cancers, but not prostate cancer in general. The relative risk of such cancers in men who consume milk is 2-3 times that of the general population, whose absolute risk is about 2-3% of dying from the disease over a lifetime. The fact that calcium consumption seems more strongly linked to such cancers than milk itself suggests that calcium may play a specific role, says Edward Giovannucci, who has studied milk consumption and prostate cancer.

Breast cancer

Scientists had hypothesized that breast cancer and milk consumption would be related, either because of IGF-1 or estradiol in milk and the hormonal sensitivity of many breast cancers. However, epidemiologic studies have shown no relationship between the two.

Osteoporosis

Multiple studies have shown that dairy consumption decreases the risk of osteoporotic fractures. Studies have also shown, however, that calcium supplementation can have the same effect.

Acne

When Clement Adebamowo and his colleagues looked at the children of those enrolled in the Nurses' Health Study, they found higher rates of acne among girls who consumed milk. They were at a loss for an explanation for their findings until they began looking at testosterone, which would presumably have less of a dramatic effect in boys because of endogenous production.

Twinning

Long Island Jewish Medical Center obstetrician/gynecologist Gary Steinman has published studies finding that women who consume dairy are up to five times more likely to give birth to twins as those who don't. "The key ingredient seems to be IGF," which sensitizes the ovaries to gonadotropin and leads to double ovulation, says Steinman. He suggests that women who are trying to get pregnant switch to soy milk.

Colon cancer

Cohort studies have suggested a protective effect against colorectal cancer for milk, perhaps decreasing the risk by about 15%. A randomized, controlled trial of dairy products supports that idea, although case control studies have not confirmed the results.

Heart disease

Results are conflicting. On the one hand, dairy intake, perhaps because of its high protein content, may decrease the risk of metabolic syndrome, ischemic heart disease, and stroke. On the other, it may increase LDL cholesterol levels. Fermented milk seems to lower cholesterol and blood pressure in those with hypertension.