Most authoritative ever report on bowel cancer and diet: Links with meat and fibre confirmed

(Medical Xpress) -- The most authoritative ever report on bowel cancer risk has confirmed that red and processed meat increase risk of the disease and concluded that the evidence that foods containing fibre protect against bowel cancer has become stronger.

The report, released as part of World Cancer Research Fund/American Institute for Cancer Research’s (WCRF/AICR) groundbreaking Continuous Update Project (CUP), has examined the links between bowel cancer risk and diet, physical activity and weight, and updated the bowel cancer findings of the WCRF/AICR’s 2007 Expert Report, Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective.

A systematic review of the evidence was carried out by WCRF/AICR-funded scientists at Imperial College London, who added 263 new papers on bowel cancer to the 749 that were analysed as part of the 2007 Report. An independent Expert Panel then reviewed the results and made judgements.

For red and processed meat, findings of 10 new studies were added to the 14 studies analysed as part of the 2007 Report. The Panel confirmed that there is convincing evidence that both red and processed meat increase bowel cancer risk.

WCRF/AICR recommends that people limit consumption to 500g (cooked weight) of red meat a week - roughly the equivalent of five or six medium portions of roast beef, lamb or pork - and avoid processed meat.

The Expert Panel behind the CUP’s judgements also concluded that the evidence that foods containing dietary fibre reduce bowel cancer risk has become stronger since the publication of the 2007 report. They considered the evidence sufficient to strengthen the conclusion that foods containing fibre protect against bowel cancer from “probable” to “convincing”.

The analysis for fibre included adding seven more studies to the existing eight from the 2007 Report, and the result was that the evidence became much more consistent.

This strengthens WCRF/AICR’s recommendation for people to consume a plant-based diet including foods containing fibre, such as wholegrains, fruits, vegetables and pulses such as beans.

The Panel also confirmed that the evidence published since 2007 did not change the judgements that there is convincing evidence that being physically active reduces risk of bowel cancer and that excess body fat – especially around the waist – remains a convincing cause of bowel cancer. There is also convincing evidence that alcohol consumption increases bowel cancer risk in men and it also probably increases risk in women.

Professor Alan Jackson, Chair of the WCRF/AICR Continuous Update Project (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 judgements 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.

“On meat, the clear message that comes out of our report is that red and processed meat increase risk of bowel cancer and that people who want to reduce their risk should consider cutting down the amount they eat.”

Teresa Nightingale, General Manager of WCRF, said: “Many people feel confused about cancer prevention because it can seem like a new study is published every week that suggests that a new substance either causes or prevents cancer.

“But the CUP takes the latest scientific findings and adds them to the existing body of evidence in a way that ensures our advice takes the latest research into account. This means people can be confident that our recommendations are up-to-date as well as being the most evidence-based information on cancer prevention available anywhere in the world.

“This latest report shows that there is enough evidence to recommend that people can reduce their bowel cancer risk by consuming less red and processed meat and alcohol, having more foods containing fibre, and by maintaining a healthy weight and being regularly physically active. This report confirms that bowel cancer is one of the most preventable types of cancer and we estimate that about 43 per cent of bowel cancers cases in the UK could be prevented through these sorts of changes. That is about 17,000 cases every year.”