Diet and cancer are directly linked, with alcohol and red and processed meats posing particular risks, according to the World Cancer Research Fund's (WCRF) study released this week.
A panel of world-renowned scientists looked at 7,000 studies published since the 1960s. Entitled Food, Nutrition, Physical Activity, and the Prevention of Cancer, the report includes 10 recommendations on how to prevent cancer.
One of the major conclusions drawn is that red and processed meat cause colorectal cancer. This is based on results that show, on average, people who ate the most red or processed meat had about a 30 per cent increased cancer risk compared with those who ate the least.
The report recommends processed meats be eaten sparingly and suggests an average intake of no more than 500g each week of red meat. According to the British Medical Journal, the current average intake in Britain is about 970g a week in men and about 500g a week in women.
Deputy chief medical officer, Dr Fiona Adshead, who is in charge of delivering on the UK government's obesity target, said: "We want to see the positive work by the food industry continued with more and more retailers and manufacturers adopting the traffic light model to make it easier for people to make the right food choices.
"There is no single solution to tackle obesity and it cannot be tackled by government action alone. We will only succeed if the problem is recognized, owned and addressed at every level and every part of society."
The report has sparked a reaction from the food industry all over the world. Julian Hunt, director of communications at the UK's Food and Drink Federation, said that balance is the key to a healthy lifestyle.
"This report confirms what most of us already knew: the secret of a healthy lifestyle is to enjoy a balanced diet, coupled with moderate amounts of exercise," he said.
"The food and drink industry has long been committed to playing a positive role in improving the health of the nation, focusing on those areas where we can make the biggest difference. Our industry is now widely recognised as leading the world when it comes to reformulating products."
However he said the problem has to be dealt with across the board, with industry, government, and individuals making changes. He concluded: "While our work is making a significant contribution to the UK's health agenda, the report is a timely reminder that government, and others, need to do much more."
The American Meat Institute (AMI) has called the WCRF panel recommendations on meat consumption "extreme" and "unfounded". The institute said the advice to limit red and processed meats reflected their anti-meat bias.
AMI foundation vice president of Scientific Affairs Randy Huffman, said: "No health groups should be dispensing clear-cut recommendations on specific foods when studies continue to contradict each other time after time…Given the complexities and conflicting research findings, it is inconceivable that WCRF could draw definitive conclusions and make such precise recommendations about specific food categories."
He referred to a study on red meat and colon cancer carried out by the Harvard School of Public Health in 2004 involving 725,000 men and women, which showed no relationship between the two.
The WCRF report includes other recommendations and notably that maintaining a healthy weight is one of the most important things you can do to prevent cancer.
Prof Sir Michael Marmot, chair of the WCRF panel said: "We are recommending that people aim to be as lean as possible within the health range, and that they should avoid weight gain throughout adulthood. This might sound difficult, but this is what science is telling us more clearly that ever before."
Other findings in the report include stronger evidence that alcohol is a cause of cancer and that dietary supplements are not recommended for cancer prevention.
It also identifies several foods and nutrients for which evidence exists on preventing cancer. For example, foods rich in folate may reduce the risk for cancer of the pancreas, and diets rich in calcium may reduce the risk for colorectal cancer.
Mothers are advised to breastfeed exclusively for six months and to continue with complementary breastfeeding after that. As well as convincing evidence that this protects the mother against breast cancer, there is also probable evidence that it protects the child against obesity in later life.