The risk of breast cancer is dramatically increased by consumption of animal products and reduced by vegetable products, sunlight and vitamin D, according to William B. Grant, PhD, an independent researcher who studies dietary and environmental links to chronic diseases.

The study of breast cancer mortality rates and dietary factors for 35 countries, published in the journal Cancer, shows evidence that diet is the most important risk factor for breast cancer.

The fraction of daily calories derived from animal products shows a strong link to increased mortality from breast cancer, while the fraction derived from vegetable products shows an equally strong correlation with a decreased mortality, according to Grant.

Some previous studies have shown a link between dietary fat and the incidence of breast cancer, while other types of cancer studies do not show this effect. Grant claims the increase is because those females living in countries with high-fat diets eat a higher fraction of animal products, drink more alcohol, and eat less fish than women living in countries with low-fat diets.

Over the course of their lives, the women on high-fat diets produce more estrogen and more insulin-like growth factor, both known to be strong factors linked to an increased risk of breast cancer, with alcohol increasing the effects of estrogen.

Grant's study also shows that exposure to ultraviolet-B radiation from the sun, which produces vitamin D, reduces the mortality from breast cancer. The mortality rates from breast cancer in the southwestern U.S. are only half of what they are in the northeast, and, in Europe, breast cancer mortality rates increase with increasing latitude.

The most cost-effective way to reduce breast cancer mortality rates for adult women is likely by obtaining sufficient ultraviolet-B radiation without burning and the use of vitamin D supplements, especially in winter in the northeast U.S. and northern Europe, according to Grant.

Other Sources: Cancer, W.B. Grant