A unique study of breast cancer mortality rates and dietary factors for 35 countries published January 1 in the journal Cancer presents strong evidence that diet is the most important risk factor for breast cancer.
Specifically, the data from the study shows that the fraction of daily calories derived from animal products exhibits a very strong correlation with increased mortality by this cancer, while the fraction derived from vegetable products shows an equally strong correlation with a decreased mortality.
This new study finally solves the mystery of why almost all such correlation type studies find a very strong link between dietary fat and the incidence of breast cancer, while other types of cancer studies, such as those involving case-control or the examination of cohorts do not show this effect.
The increase is due to the fact that those females living in countries with high-fat diets generally eat a higher fraction of animal products, drink more alcoholic beverages, and eat less fish (a source of vitamin D) than those women living in countries with low-fat diets.
Thus, over their lifetime, they produce more estrogen- and more insulin-like growth factor (IGF-1). Both of these compounds are known to be strong factors associated with increased risk of breast cancer, and alcohol increases the effects of estrogen.
The study also confirms surprising and important results about the relationship between the mortality from breast cancer and ultraviolet-B (UV-B) radiation, the type of sunlight that produces vitamin D (and is also associated with tanning and skin cancer).
The results clearly show that exposure to UV-B actually reduces the mortality from breast cancer quite substantially.
For example, breast cancer mortality rates in the southwestern part of the U.S. are only half what they are in the northeast, and, in Europe, the breast cancer mortality rates are found to increase with increasing latitude as long as corrections are made for diet.
Thus, the most cost-effective way to reduce breast cancer mortality rates for adult women in the U.S. and Europe is likely by sufficient UV-B radiation without burning and the use of vitamin D supplements, especially in winter in the NE U.S. and northern Europe.
The study was conducted by William B. Grant, Ph.D., an independent research scientist who studies dietary and environmental links to chronic diseases.
Using correlation analyses based on the sophisticated tools developed to study the effects of atmospheric pollution, Dr. Grant, in 1997, published the first paper linking a high-fat, high-caloric diet to the development of Alzheimer's disease. (W.B. Grant, Dietary links to Alzheimer's disease. Alzheimer's Disease Review 2, 42-55, 1997; available online at this URL.)
(Reference: W.B. Grant, An ecologic study of dietary and solar UV-B links to breast cancer mortality rates. Cancer, 94, 272-281, Jan. 1, 2002.)
[Contact: William B. Grant Ph.D. ]