A diet high in fat is not by itself likely to cause breast cancer, suggests a study in the Journal of Epidemiology and Community Health. But it is likely to deplete the body of an essential nutrient, a factor that is probably responsible for most cases of the disease, concludes the research.

The author examined all the relevant epidemiological and biological data in support of current evidence about breast cancer, the main cause of which is still unknown. Other factors, such as obesity, first motherhood over the age of 30, childlessness, and radiation, account for only a small proportion of cases, and are probably secondary to the factors that determine risk, he says.

Genes are not the answer, because there is a low prevalence of family history and women with similar genetic profiles develop the disease at different rates when they move to other countries. The data do not incriminate pollution or infection as the causes. While oestrogen is implicated in the development of the disease, the published evidence points to its promoter rather than causal role. But there is evidence for dietary factors, especially fat, says the author.

Although a causative factor is yet to be identified, the hypothesis that best fits the epidemiological data, concludes the author, is that dietary fat depletes breast tissue of an essential factor that normally protects against the development of the disease. This works in tandem with age and the effects of oestrogen.

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BMJ Specialty Journals
17-Oct-2000