Taking dietary supplements does nothing to protect people from cancer, according to a major new report published yesterday.
The report from the World Cancer Research Fund, which reviewed about 7,000 studies from across the globe on the link between diet and cancer, found that taking high dose dietary supplements of some nutrients could in fact increase one's risk of getting different cancers.
The studies were reviewed by a panel of 21 world-renowned scientists who concluded that maintaining a healthy weight is one of the most important things people can do to prevent cancer.
The panel made 10 key recommendations, the main one being that people should remain as lean as possible and avoid weight gain throughout adulthood. Physical activity should be part of everyday life as it helped to lower cancer risk, recommending 30 minutes of vigorous activity a day.
The report also recommends people should limit consumption of energy-dense foods such as treats and avoid sugary drinks. They should eat at least five portions of fruit and vegetables a day and limit intake of red meats and avoid processed meats. They should also limit salt intake.
In addition, the report recommends men limit alcohol intake to two drinks a day and women limit it to one drink a day.
The panel of experts said there was now convincing evidence that body fat is a cause of at least six cancers including bowel and post-menopausal breast cancer, as well as cancer of the oesophagus, pancreas, womb and kidney.
The report said there was convincing evidence that processed meats including ham and bacon increase the risk of bowel cancer. "People who consume them are advised to do so sparingly," it said.
It also said the evidence that red meat was a cause of bowel cancer was stronger than ever. "People should not eat any more than 500g of red meat (cooked weight) a week," it said.
It also advises mothers to breastfeed exclusively for six months and to continue with complementary breastfeeding after that. "This is because of convincing evidence that breastfeeding protects the mother against breast cancer and probable evidence that it protects the child against obesity later in life."
Prof David Shuker from the Open University in Britain was one of the panel of 21 experts which reviewed the data.
There had been a great deal of publicity around obesity but the fact was that putting on weight could increase your cancer risk, even if you were still within the healthy range. People should remember to eat a balanced diet, he advised, but they should also avoid being underweight.
The 7,000 studies were conducted at nine academic institutions across the world in places such as the US, Britain, the Netherlands, and Italy.
Norma Cronin, health promotion manager with the Irish Cancer Society, said the message from the report was clear that any increase in weight could increase one's risk of cancer. One shouldn't forget, however, that tobacco was still the most important preventable cause of cancer.
About 23,000 people in the Republic develop cancer each year.
Martin Higgins, chief executive of safefood, the Food Safety Promotion Board, said more than half of the meat consumed on the island of Ireland was processed. "Given the new evidence in this report, safefood advises that processed meats should be consumed sparingly," he said.
Meanwhile a separate survey published yesterday found more than a third of Irish people believed lung cancer patients brought the disease on themselves. The findings of the TNS-mrbi survey were published to mark the start of World Lung Cancer Awareness Month.