The recent death of vegetarian Linda McCartney has highlighted the issue of vegetarianism and breast cancer. Numerous studies have found that a vegetarian diet protects against breast cancer one showing a 50 per cent decline in premenopausal breast cancer among vegetarians (Cancer, 1989; 64: 582-90; Br J Cancer, 194; 70: 129-32; Am J Epidemiol, 1988; 127: 440-53.).
However, one little publicised finding of Thorogood's 1996 study (see p 2) was an increase in the death rate from breast cancer among vegetarian women, which the authors were unable to explain. Although the presumption is that the lower fat intake of vegetarians accounts for low levels of breast cancer, a pooled analysis of studies of fat intake and the risk of breast cancer showed no association (N Eng J Med, 1996; 334: 356-61).
In a recent article, Professor Tom Sanders, Department of Nutrition and Dietetics, King's College, London, quotes two studies which dispute the claim that vegetarian women are less likely to be victims of breast cancer (Nutri Bull, 1998; 23: 88-93). One showed an excess of breast cancer among members of the Vegetarian Society. In the other, Dr Tim Key of the Imperial Cancer Research Fund reported a significant increase in the risk of breast cancer in vegetarian health food shop consumers, compared with those who eat meat. Key is also quoted as saying that studies into Seventh Day Adventists do not support the idea that vegetarianism reduces the risk of breast cancer at best, says Key, there is no difference between Adventists and the rest of the population. Published evidence is, in short, contradictory. To draw firm conclusions, researchers need to control for other factors, such as the number of children a woman has and breastfeeding, which protect against breast cancer, and such clear risk factors as hormone consumption, in the form of HRT or the Pill.