Diverse Influences of Dietary Factors on Cancer in Asia


The major environmental risk factors for cancer are carcinogen and co-carcinogen exposure in tobacco,insufficient exercise and above all an unhealthy diet. What we eat or do not eat is exceedingly important indetermining what cancers or other chronic disease we may suffer from. Carcinogens may be integral contaminantsof the diet, like nitrosamines in some situations and aflatoxins, or may be generated by cooking processes, as isknown to be the case for heterocyclic amine pyrolysis products. Examples of co-carcinogenic agents may includegrit in bread products, salt in pickles or betel in chewing quids. Dietary insufficiencies, for example of zinc, mayalso act to increase sensitivity to genetic damage, for example. Influence on metabolism of carcinogens, likeinduction of phase II enzymes like glutathione S transferases, further directly impacts on carcinogenicity.Antioxidants in fruits and vegetables are typical examples of protective agents acting in this way. In addition wehave dietary fibre which can decrease carcinogen exposure through accelerating passage of faeces through thegut. Other types of fibre, the soluble forms, can act to decrease uptake of glucose and thus suppress insulinexposure, an important factor for colon cancer. Natural anti-inflammatory agents like N-3 fatty acids in fishoffer another example of preventive factors in the diet. Individual dietary components, like isoflavones in soyproducts, can interfere with hormone function to exert a beneficial action, as on the breast. Other compoundsmay act via stimulation of the immune system like lactoferrin and betaglucans. Perhaps the most importantinfluence of diet on cancer, however, in a world of increasing comfort and ease of access to foodstuffs, is throughover-eating and consequent obesity. Given the importance of diet to all our lives, we need to focus on all possibleinteractive effects in providing an evidence base to guide our choices regarding what we should eat in Asia.