High Fiber
Does eating a high-fiber diet help prevent breast cancer?
This is not known. The combined evidence from over a dozen large research studies says "probably not." But a definitive conclusion has not been reached. Whole-grain breads and cereals may reduce the risk of cancers of the digestive system. Several studies have looked for a similar protective effect for breast cancer, but none has been found.
The data on fiber intake are unclear because the studies done on the correlation between fiber and breast cancer have some limitations. The average American woman eats 12 grams of fiber a day. Some experts have theorized that an increase to 30 or 35 grams of fiber a day might lower the risk of breast cancer by as much as 15% over a 10-year period. The evidence from the largest research studies does not show that this will happen, but it doesn't rule it out, either. So few American women eat this much fiber that it hasn't been possible to find enough of them to determine if their rate of breast cancer differs from that of the average woman.
Is there evidence that a high-fiber diet might reduce the risk of breast cancer?
Evidence does exist that implies a beneficial relationship between a high-fiber diet and breast cancer. But the data in some studies are not definitive -- quite possibly because the diets of the populations being studied have changed over the past 20 years. This is an important point because the small changes in individual breast cells (proliferative breast disease) that increase the future risk of breast cancer occur among women in their thirties and forties. However, the importance of fiber to health became widely known only 20, or so, years ago. Therefore, women who are now getting breast cancer (those in their fifties and sixties) would not have been eating a high fiber diet at the time that the cell changes first occurred.
One Australian study reported that women who eat the most fiber are more likely to have a biopsy diagnosis of nonproliferative breast disease (the type that is not associated with breast cancer) than proliferative breast disease. Would eating more fiber before menopause lead to less breast cancer after menopause? No one really knows. Eating a high fiber diet does reduce the risk of cardiovascular disease and decreases a variety of digestive problems.
