Eating Meat Can Cause Cancer - the Meat Cancer Link
Meat and fat
Figures for food consumption and cancer incidence and mortality rates in different countries show fairly close correlations between the consumption of fat and, to a less extent, the consumption of meat and the incidence of several types of cancer. The correlations are closest for breast cancer and cancer of the large bowel and are less strong for cancers of the endometrium, pancreas, and prostate. When, however, attempts are made to associate the consumption of either type of food with the disease in individuals within a country the evidence is commonly conflicting. This could be because the international correlations are misleading, indicating only that the risks are correlated with something that is correlated with fat and meat consumption (for example some other aspect of a high gross national product), but it
could be partly because of the inaccuracy of dietary histories and partly because people in developed countries, and particularly in North America, eat such similar diets. Overviews of the published data, however, do suggest that a high consumption of fat is associated with a high risk of colorectal cancer, but the claim that a high consumption of fat (or of particular types of fat) is associated with high risks of breast and endometrial cancer after the menopause, other than by providing a high calorie diet leading to obesity, is controversial.
Overnutrition
That overnutrition could affect the incidence of cancer was first suggested by Tannenbaum's experiments on mice during the Second World War. These showed that the incidence of spontaneous tumours of the lung and breast and of a variety of tumours produced experimentally could be halved by moderately restricting the intake of food without modifying the proportions of the individual constituents. This protective effect has subsequently been demonstrated repeatedly, but has attracted little attention (perhaps because reports of such results emphasized the benefits of restriction rather than the harm of overeating). It is now clear, however, that what is considered normal nutrition in developed countries increases the risk of breast cancer (by bringing forward menarche and increasing body size) and possibly also that
of testis cancer. With greater consumption obesity (that is a BMI greater than 25 kg/m 2) has been estimated to be responsible for 5 per cent of all incident cases in Europe and 10 per cent of all cancer deaths in non-smokers in the United States (Peto, 2001): most notably cancer of the breast in women after the menopause and cancers of the endometrium, large bowel, pancreas, gallbladder, prostate, and kidney and myelomatosis. For some of these increases, the explanation is obvious: namely, those of the two female cancers, which in postmenopausal women are attributable to the formation of oestrogen from androstenedione in adipose tissue while the increased risk of gallbladder cancer may be due to a greater secretion of bile salts. For others, the explanation is obscure. |