This very large study of the effects of diet on the incidence of breast cancer was just published today in The Journal of the American Medical Association and has received much media attention, including this article in the Los Angeles Times. The study is important because of its size (over 48,000 women were studied) and because it was one of the few studies of the effects of dietary change that actually involved randomizing women into the low fat or the standard diet group. This randomization makes the results much more reliable than studies in which the subjects decide themselves what to eat.
The results showed the same incidence of breast cancer in both groups of women. Approximately one in every 230 women in each group developed breast cancer.
Some are interpreting the study with caution, warning that the women in the low-fat diet group may have still had too much fat in their diets to decrease their risks, but if that’s the case, it’s probably not realistic to expect women to lower their dietary fat much further. The other possible interpretation is the obvious one: that there is no link between dietary fat and breast cancer.
Links between diet and cancer incidence have always been speculative, and in other diseases like heart disease and obesity dietary fat is being found to be less important than total calories consumed and exercise. Unfortunately, breast cancer prevention remains elusive, and the best we can do at this point is early detection.