Eating too much food high in fat, such as butter, milk and meat, could put women at a higher risk of breast cancer, according to a paper published today.
Scientists writing in the Lancet medical journal say that the link has until now been hidden by the imprecise way in which scientists collect information on what people eat. Past studies have shown no evidence that women who eat more biscuits, cakes, burgers or other high fat foods are more prone to get breast cancer than others whose fat intake is low.
The new research discovered, however, that women who eat 90g of fat per day have twice the risk of developing breast cancer of those who eat less than 40g of fat per day. 90g of fat is roughly equivalent to two beefburgers, one small packet of crisps, a large bar of milk chocolate and one and a half digestive biscuits.
"Our study shows there is an emerging link between eating too much fatty food and increasing the risk of breast cancer," say Sheila Bingham from the Medical Research Council's Dunn Human nutrition unit in Cambridge and colleagues.
"The effect seems to be related particularly to saturated fat found mostly in high fat milk, butter, meat and some cereals such as biscuits and cakes. We believe that, in the past, finding links between breast cancer and fat intake has been hampered by imprecise research methods which appear to have obscured a link between the two."
It is not easy for scientists to be sure what people are eating, they say. Researchers studying diet have traditionally given out food frequency question naires, asking how often their subjects eat particular kinds of foods.
These have invariably shown no increased cancer risk from eating more or particular types of fatty food.
But studies in animals and comparisons between countries where fat consumption is high, as it is in the UK, and those where it is low, as it is in underdeveloped countries, suggest there is a link between fat and breast cancer. Dr Bingham's team determined to find out whether the information being collected in nutritional studies was flawed.
They analysed data provided by a major piece of research called the European Prospective Investigation of Cancer and Nutrition (EPIC). Between 1993 and 1997, 25,630 men and women in Norfolk aged between 45 and 74 were enrolled. They had a health examination, filled in food frequency questionnaires and completed a seven-day food diary.
The data from the questionnaires showed no link between fat intake and cancer. When the scientists analysed the food diaries, however, and calculated the true amount of fat consumed each day, a link emerged. "We believe that the comprehensive food diaries that our Norfolk participants completed give a more accurate picture of eating habits compared to other methods," said Dr Bingham.
Dr Lesley Walker, Director of Science Information at Cancer Research UK, said: "Studying the link between diet and cancer is a complex business.
"The EPIC study continues to uncover more information about how the two can be connected. This research highlights the importance of eating sensibly to reduce cancer risk."
