|International Vegetarian Union (IVU)|
Diet and Cancer
The first global report on diet and cancer, published in September 1997 by the World Cancer Research Fund in association with the American Institute for Cancer Research, is a hugely impressive document. Food, Nutrition and the Prevention of Cancer: a global perspective is a 650 page report prepared by an international panel of 15 scientists from nine countries, supported by over 100 reviewers, who assessed more than 4,000 studies of diet and cancer.
The report estimates that dietary change could reduce global cancer incidence by 30 to 40 per cent, equivalent to three to four million cases per year worldwide. Together with a cessation of smoking this means that 60 to 70 per cent of cancers are preventable.
Most of the report consists of an assessment of the links between a wide range of foods and drinks, nutrients, methods of food processing and storage, body size and level of physical activity, and each of eighteen common cancers. For factors judged to either increase or decrease the risk of a given cancer the strength of the association is classified as "convincing", "probable" or "possible". In general, plant foods reduce the risk of cancer. For example, vegetables reduce the risk of cancer of the mouth and pharynx, oesophagus, lung, stomach, colon and rectum (convincing), larynx, pancreas, breast and bladder (probable), liver, ovary, endometrium, cervix, prostate, thyroid and kidney (possible). Similarly, fruits reduce the risk of cancer of the mouth and pharynx, oesophagus, lung and stomach (convincing), larynx, pancreas, breast and bladder (probable), ovary, endometrium, cervix and thyroid (possible). In contrast, alcohol, meat, dietary fats and obesity increase the risk of various cancers. Meat, for example, probably increases the risk of colorectal cancer, and possibly in creases the risk of cancers of the pancreas, breast, prostate and kidney.
Studies of vegetarians show that they have a decreased incidence of cancer in general and at several specific sites after allowing for the effects of other lifestyle factors such as smoking and amount of exercise. These benefits are due not only to the exclusion of meat, but also to the inclusion of a greater quantity and variety of plant foods containing a wide range of cancer preventive substances.
The panel make a total of fourteen dietary recommendations aimed at both policymakers and individuals. For example, individuals are advised to:
-- Choose predominantly plantbased diets rich in a variety of vegetables and fruits, pulses (legumes) and minimally processed starchy staple foods (Rec. 1)
-- Maintain a reasonable body weight (body mass index, a measure of relative weight calculated by dividing your weight in kilograms by the square of your height in metres, should be between 18.5 and 25 kg/m 2 ) (Rec. 2)
-- Take an hour’s brisk walk or similar exercise daily, and also exercise vigourously for at least one hour per week if occupational activity is low or moderate (Rec. 3)
-- Eat 400-800 grams (15-30 ounces) or five or more portions (servings) a day of a variety of vegetables and fruits, all year round (Rec. 4)
-- Eat 600-800 grams (20-30 ounces) or more than seven portions (servings) a day of a variety of cereals (grains), pulses (legumes), roots, tubers and plantains. Prefer minimally processed foods. Limit consumption of refined sugar (Rec. 5)
-- Limit alcoholic drinks, if consumed at all, to less than two drinks a day for men and one for women (Rec. 6)
-- Limit intake of red meat, if consumed at all, to less than 80 grams (3 ounces) daily (Rec. 7)
-- Limit consumption of fatty foods, particularly those of animal origin (Rec. 8)
-- Limit consumption of salted foods and the use of cooking and table salt (Rec. 9)
Other recommendations relate to the storage and preservation of food (Rec. 10 & 11), the monitoring and enforcement of safety limits for food additives, pesticide residues and other chemical contaminants in food (Rec. 12), the avoidance of charred food (Rec. 13), and the use of dietary supplements which are judged to be “probably unnecessary, and possibly unhelpful, for reducing cancer risk” (Rec. 14). Individuals are also advised to neither smoke nor chew tobacco.
The report is not a vegetarian manifesto, but it clearly identifies a diet based on plant foods as the best for cancer prevention. A lowfat vegetarian or vegan diet, allied to physical exercise, maintenance of a reasonable body weight and the avoidance of tobacco, represents a lifestyle perfectly in line with the recommendations of this landmark publication.
Paul Appleby, Oxford Vegetarians, c/o 57 Sharland
Close, Grove, Wantage OX12 OAF, UK,
You can order a copy of 'Food , Nutricion and the Prevention of Cancer: A Global Perspective' at the special discount rate of $35 (including shipping and handling) at: American Institute for Cancer Research, 1759 RStreet NW, Po Box 97167, Washington DC 20090-7167, USA