In the 1960s, researchers first described a correlation between fiber and colon cancer after observing groups in Africa who ate a lot of fiber and presented low incidence rates of colon cancer. The researchers suggested that the correlation may be attributed to the fact that fiber moves stool more quickly out of the bowel. Intuitively, the theory made sense, said Giovannucci, but experts didn't conduct prospective epidemiological studies until the last 10 years. Folate intake may prove much more important than fiber in reducing colon cancer risk, he said. If tumors in the colon form, aspirin seems to arrest their growth rate, said Giovannucci.
Cells produce compounds called prostaglandins that promote cell division in the colon.
Aspirin may inhibit prostaglandins so that the cell division slows or stops, but to achieve the effect, people most likely would have to start taking the aspirin at age 40 and not stop. Giovannucci said that a steady diet of aspirin can cause unpleasant and dangerous side effects in some people such as bleeding in the stomach. Some people may prefer aspirin over a colonoscopy. He added that the hypothesis is not proven, but animal studies offer compelling support. March is National Colorectal Cancer Awareness Month.