RISK FACTORS FOR BREAST CANCER: GENETIC PREDISPOSITION, GEOGRAPHIC DIFFERENCES AND DIET
Genetic predisposition
Some 5 per cent of breast cancers are related to an abnormal gene. Although this gene is rarely implicated in postmenopausal women who develop breast cancer, it is much more commonly present in pre-menopausal women with this disease, particularly in those under the age of 30.
Your risk of developing breast cancer is higher if you have a close relative with pre-menopausal breast cancer than if an affected relative is older than 50. The risk increases if you have two relatives with pre-menopausal breast cancer or one with the disease in both breasts.
The breast cancer family gene which has been identified is found not only in families with cancer of the breasts, but also in those with ovarian and colon cancer. Families with this gene should be given specialist advice and counseling at clinics run by geneticists or breast surgeons.
Geographic differences
Breast cancer is about eight times more common in Northern Europe, North America and Australia than it is in parts of Asia and Africa. However, women who move from low-risk countries, such as Japan, to high-risk countries such as North America, show a sometimes immediate increase in risk – certainly within one or two generations. Although this does not rule out the possibility of a genetic predisposition, it does seem to indicate an important role for some factor(s) in the environment.
Some dietary factor(s) may play a part in the increase in risk. Although it is not known how these exert their effects, it may be that they influence hormone synthesis or metabolism.
Many foods contain hormones or hormone analogues, either naturally or otherwise. For example, milk is a hormone-derived substance, as, therefore, are butter and cheese etc. Chickens and pigs are often injected with hormones which may be present in the meat from these animals. The early oral contraceptive pill was made from hormones naturally present in the sweet potato. Ginseng also contains naturally occurring oestrogen. These are just a few examples.
There is evidence to suggest an association between diet and various cancers, including cancer of the breast, although this is not conclusive and some studies have failed to find any such link.
Other studies suggest that a diet high in fat and in animal protein, common in most countries in the more affluent West, may be a significant factor in the development of this disease, although there is as yet no conclusive proof of this. Although the Japanese are now a well-nourished nation, they do not eat a large amount of animal fat, and, as mentioned above, do not have a high incidence of breast cancer when living in their own country.
It is also possible, but unproven, that vitamins A and C, found in dark green and yellow vegetables and in fruit, may have a protective effect.
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Tags: Cancer