Giving fibre supplements to patients with a history of growths in their colon may actually increase rather than reduce the problem. Many doctors believe that most colorectal cancer develop out of polyps, or adenomas, which grow on the wall of the bowel.
However, the latest research, conducted in France, Denmark, Italy and Germany, suggests that new adenomas are actually more likely to grow in patients given this fibre supplementation. In 456 patients with a history of polyps, roughly a third each were given extra fibre, extra calcium, or nothing at all.
Three years later, the patients were given a second colonoscopy to see if any new polyps had appeared. In the group given no supplements, 36 out of 178 had new polyps, while 58 out of 198 in the fibre group had new growths. However, in those given calcium supplementation, only 28 out of 176 had new polyps.
In particular, high consumption of red meat is associated with a higher risk of developing this form of cancer. Some other studies have suggested that eating vegetables, whole-grain cereals and calcium have a protective effect. Dr Tim Key, expert on diet and cancer with Imperial Cancer Research Fund, said: "Colorectal adenomas are growths in the large intestine which are not cancerous, but some adenomas do eventually grow and turn into cancers. The recommendation remains that healthy diets should be high in vegetables, fruits and cereals." He added: "This trial has no clear implications for the development of colorectal cancer, because most adenomas do not turn into cancers."