Leading scientists say there is more evidence than ever before that fibre-rich foods prevent bowel cancer.
Following analysis of the most up-to-date research on the disease, experts said there is now “convincing” evidence that foods containing fibre can offer protection.
This is stronger than a 2007 conclusion that dietary fibre “probably” cuts the risk of the disease.
New evidence includes research that says three servings a day of cereal fibre and wholegrains reduces the risk.
The World Cancer Research Fund, which commissioned experts from Imperial College London to look at the data, said it recommended people eat a plant-based diet including fibre-rich foods such as wholegrains, fruits, vegetables and pulses such as beans.
Scientists also analysed new data on the risk of bowel cancer from red and processed meat, which adds weight to the view these are a “convincing” cause of the disease.
The WCRF and the American Institute for Cancer Research recommend people eat no more than 500g (cooked weight) of red meat a week. This is the equivalent of about five or six medium portions of roast beef, lamb or pork. They say people should avoid processed meat.
Meanwhile, the latest analysis said milk, calcium and garlic probably protect against bowel cancer, but the evidence on whether sugar, cheese or foods containing animal fats cause the disease is limited. There is also a repeated warning that alcohol is a known cause of bowel cancer in men and is a probable cause in women. And there is increased evidence that exercise cuts the risk of bowel cancer, but being fat – including around the abdomen – raises the risk.
The report is part of the WCRF’s Continuous Update Project and updates the bowel cancer findings in its 2007 report: Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective.
Overall, the new analysis adds 263 new papers on bowel cancer to the 749 that were studied as part of the 2007 report.
Professor Alan Jackson, chair of the CUP expert panel, said: “Our review has found strong evidence that many cases of bowel cancer are not inevitable and that people can significantly reduce their risk by making changes to their diet and lifestyle.
“Because our judgments are based on more evidence than ever before, it means the public can be confident that this represents the best advice available on preventing bowel cancer.
“There has been a lot of debate over the last few years about the strength of evidence that red and processed meat increase risk of cancer.
“We hope our review can help give clarity to those people who are still confused about the strength of the evidence.”
Deborah Alsina, chief executive officer of Bowel Cancer UK, said: “The report significantly adds to the available evidence into the increased risk of bowel cancer from eating too much red and processed meat; and strengthens the evidence of how eating food with fibre in it protects people against the disease.
“We share the WCRF’s recommendations of the amount of red meat people should eat and agree that processed meat should best be avoided.
“We also recommend that people eat more fibre as part of a healthy diet and look forward to hearing more evidence of its potential role in helping to prevent the disease.”