Additional questions were asked with more prompting to see whether the numbers improved. When subjects were asked to consider dietary steps specifically, rather than mammograms or any other factor, the number citing reducing intake of fat or meat, or increasing intake of vegetables, fruit, fiber, or vegetarian meals increased to 37 percent in 1991 and to 52 percent in 1995. This increase is significant, although these figures still pale in comparison with the number of Americans who are aware of the links between diet and heart disease. Again, differences in response rates by age, race, income, and education were apparent. Countries where fattier diets are consumed have much higher breast cancer rates, presumably because fat in foods increases the amount of estrogen in the blood.
Fiber reduces estrogen levels.
Federal cancer authorities hold that the evidence linking diet and breast cancer is strong and publish limited informational materials for the public. However, mammography and self-examination have been much more aggressively promoted by governmental agencies and private groups. The survey did not address the possibility that some women were aware of theories linking diet and breast cancer but did not believe the evidence. A large study of nurses conducted by Harvard University, for example, failed to detect any relationship between dietary fat and breast cancer, a result that has been attributed to the fact that the subjects in that study did not vary greatly in their dietary habits. International comparisons and case-control studies show an important role for diet in breast cancer.