More recently, a randomized controlled trial was done by Dr. Richard Sampliner, a gastroenterologist and professor of medicine at the University of Arizona, Tucson, and his colleagues comparing the effect of a wheat bran supplement with a placebo on the recurrence of polyps. Again the fibre intake in the supplemented group was well below the amount eaten in India and Africa. The recurrence over a three-year period of observation was not reduced by wheat fibre but a careful look at the paper suggested males only seemed to have less polyp recurrence. These studies are difficult to interpret because the fibre intake levels do not reach that taken by populations with a low risk of cancer. Furthermore, polyp formation occurs over a period of years and the period of observation was probably too short.
Red meat has iron which increases oxidative stress in the bowel.
The majority of the iron in red meat is not absorbed and accumulates in the colon which therefore receives most of the oxidative stress. Methylation of DNA modifies the expression of genes. It is now recognized that hypomethylation of genes known to suppress cell proliferation reduces the action of these genes. Colon cancer is associated with reduced activity of tumour suppressor genes, and folate is important in methylating these genes and maintaining tumour suppression. There is increasing evidence that high folate intakes reduces the risk of colon cancer.