Strong evidence that a vegetarian diet does protect against all types of cancer emerged from a 12-year British study of more than 11,000 adults. It is the first time that researchers have been able to isolate diet in vegetarians as the most important factor in reducing the cancer risk, having set aside smoking, being overweight or social and financial differences in the subjects.
The same research shows that vegetarians may also have slightly less risk of developing heart disease, but it is not clear if diet alone is responsible.
Dr Margaret Thorogood, senior research fellow in the Department of Public Health at the London School of Hygiene and Tropical Medicine, who led the research, said she had been surprised by the 40 per cent finding, based on analysis of 404 deaths (94 from heart disease and 164 from cancer). She said that her initial interest had been the effects of diet on heart disease. 'But together they are the major killers in this country.'
'With just over 400 deaths, the numbers are too small to discover which cancers may be the most affected.' Her guess was that cancer of the large bowel and breast cancer could emerge as the strongest associations.
The non-meat eaters were made up of 5,728 who did not eat meat or fish or ate these foods less than once a week, vegans who ate no meat, fish, eggs or dairy products, and 387 fish eaters. For the study, published tomorrow in the British Medical Journal, non-meat eaters were recruited through advertisements in Vegetarian Society publications and newspapers. They were asked to introduce a similar meat-eating friend willing to join the control group. A total of 6,115 non-meat eaters and 5,015 controls were recruited between 1980 and 1984.
Dr Thorogood said earlier studies had shown lower death rates in vegetarians but had often used non-meat eaters recruited through religious organisations or other specialist groups, or had not eliminated possible confounding factors produced from a generally 'healthier' lifestyle. American studies have been based on Seventh Day Adventists whose lifestyle tends to be more ascetic.
Dr Thorogood is herself a 'light' meat-eater and her daughter is vegetarian, but she did not advocate that people should stop eating meat.
'I don't think one epidemiological study is strong enough for that. I think people should follow the advice being given currently, to reduce their fat intake and increase the amount of fresh fruit and vegetables they eat,' she said. Now she would like to know which types of vegetarian diet offer the most protection and she hoped to investigate both questions in the future. She also said she wanted to study the diet diaries which were kept by half of the people who died.
Dr Alan Long, honorary research advisor to Vega, a vegetarian research group and a participant in the study, is vegan and is matched with a dentist. He said: 'There may be some bias in that the study population tended to be from a higher social position. But the findings are significant because they get closer to ordinary people in this country than any other study has done.'