Although a high-fibre diet has long been known to be good for the gut and has been thought to be protective against bowel cancer, the study, published on the British Medical Journal website, is among the first to quantify the benefit.
The analysis of 25 studies, involving almost two million participants, found for every 10 gram increase in total dietary fibre, the risk of bowel cancer dropped by 10 per cent.
Experts recommend that adults should eat between18 and 24 grams of fibrea day, but the average intake in Britain is only about 15 grams. That figure also masks wide variations between those who eat a lot of fibre and a little.
The researchers, from Imperial College London and the Danish Cancer Society, concluded that "a high intake of dietary fibre, particularly from cereal and whole grains, is associated with a reduced risk of colorectal cancer".
Whole grain foods include brown and wholemeal breads, cereals, oatmeal, brown rice and porridge.
Most foods only contain a little fibre so getting enough can be difficult. Muesli, for instance, only contains about three grams per 50 gram serving.
Bowel cancer kills about 16,000 people in Britain a year, more than breast or prostate cancer.