IN THE PREVENTION OF CANCER
People who eat vegetarian or near vegetarian diets have the lowest rates of cancer in the world. A vegetarian diet comes closest to the dietary guidelines for reduction of cancer set forth by the National Cancer Institute of USA which estimates that one third of all cancer deaths in USA and eight out of ten of all cancers are related to diet. According to some estimates about 30%-40% of cancers in men and up to 60% of cancers in women are due to dietary factors (Bayer and Gragam, 1984).
Surveys have revealed that Asians and Africans have much lower incidence of breast cancer than Europeans and Americans who consume Western type diets. There is evidence to show that vegetarian diets protest against breast cancer because -
i. Vegetarians have lower levels of blood oestrogens hormones that raise the risk of breast cancer (B.K. Armstrong et al 1990).
ii. Vegetarians begin menstruation somewhat later than average and there is a longer time between periods. Dietary fat shortens the menstrual cycle while fibre increases it (Cassidy et al 1990)
iii. Soyafood consumption can block the activity of oestrogens and soya beans contain chemicals called isoflavones which act against cancer.
In Haryana it has been observed that daily consumption of green and yellow vegetables rich in beta carotene, vit C, calcium and dietary fibre lowers the risk of cancer. There has been shown a strong relationship between animal protein intake and breast cancer (Graham et al, American Journal of Epidemiology, 1991).
Colon cancer
Diet is more strongly linked to colon cancer than to any other type of cancer and vegetarians are less liable to get this disease. (Journal of National Cancer Institute, Vol. 30:1983).
In vegetarians unlike in meat eaters colon cells are much less active (The more the colon cells divide the greater the risk of cancer). Secondary bile acids which are carcinogenic are more in omnivores compared to vegetarians. Vegetarians have fewer of the bacteria that convert the harmless bile acids into ones that are carcinogenic compared to non vegetarians.
Vegetarians have lower levels of faecal enzymes that enhance the absorption of carcinogens (VG Aries et al, J. Pathology Vol. 103:1972).
Oesphagus and stomach
Although tobacco and alcohol intake are major risk factors for oesophageal cancer, low intake of vitamin A and C are also associated with increased risk of this cancer. Lack of consumption of fruits and vegetables has been linked to cancer of oral cavity. Vegetarians have higher blood levels of betacarotene which is thought to protect against cancer. Polyphenols prevent cancer of oesophagus and stomach and non vegetarian diets contain powerful carcinogens such as nitrosamines. Vitamin C found in fruit juices inhibit these carcinogens.
Cancer of prostrate
Among the men in the USA cancer of prostrate is the second most common malignancy and this cancer is not common among Seventh Day Adventist men as compared to general population, suggesting that vegetarianism is the protective factor (American Journal of Clinical Nutrition, 1994). High fibre intake decreases the risk of prostrate cancer and high fat intake raises the risk (cancer, Vol. 58, 1986)
Other cancers
Low fat diets have been shown to reduce the occurrence of non-melanoma skin cancer.
In a Japanese study of 122,000 people, meat intake increased the lung cancer risk in people who smoked. Higher blood levels of beta carotene is thought to protect against lung cancer.
Cancer of tests and ovaries have been found to be more common among people who consume large quantities of fat.
High consumption of soya-based products, dried fruit, beans, lentils (dhal) and peas has been associated with lower risk of cancer of the pancreas. Risk of bladder cancer is associated with high meat intake (American Journal of Clinical Nutrition, 1994).
There is evidence, to show that 'increasing use of meat, poultry or fish is associated with increased risk estimates for gliomas (cancer of brain).' This increased risk is especially apparent for consumption of pork products as many pork products are cured with sodium-nitrite (P.K. Mills et al, Neuroepidemiology Vol. 8, 1989).
Cancer protection diet includes less fat and more fruit especially citrus fruits, increased intake of vegetables especially those rich in carotene, and dark green vegetables such as cabbage, spinach and cauliflower, increased intake of whole grain cereals and less of salt, cured, smoked and pickled food. Consumption of fibre should be increased. Animal protein should be substituted by vegetable proteins.
Written by: Dr. D.P. Atukorale, Lanka Lake House
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