Diet Nutrition And Cancer Historical Perspectives

It is abundantly clear that diet and nutrition are important contributors to carcinogen-esis, both in humans and laboratory animals (6-10). Evidence documenting the critical role of nutrition in cancer risk began to accumulate after the separate disciplines of carcinogenesis and experimental nutrition were established in the first half of this century. During this period, the essential nutrients were identified, requirements of rodents and humans were defined, and human deficiency syndromes corrected in industrialized nations. Purified nutrients and components of foods were characterized for the preparation of carefully controlled experimental diets in laboratory animals. Scientists proceeded to examine the effects of specific nutrients on tumorigenesis in the rapidly expanding l ist of newly characterized rodent cancer models that were originally based on carcinogens found in the environment, such as the workplace. The meticulous studies from the laboratories of Tannenbaum (11-13), Boutwell (14), and McCay, during the 1930s and 1940s (15), characterized the important roles of fat and energy intake, as well as many other nutrients, in the genesis of experimental cancers (13). Although the relevance of the observations from rodent models to human cancer was frequently discussed and debated, the epidemiologic methodology needed to investigate nutrition and cancer hypotheses in humans would not be refined for several decades.

The development of food availability data and dietary surveys coupled with statistics on cancer incidence and mortality in many nations around the globe provided the first examples of provocative associations between human cancer risk and dietary intake (6-10). The observations that human cancers exhibit 10- to over 100-fold variations in incidence among different geographic and cultural areas suggested to some investigators that diet and nutrition was a critical etiologic factor. This concept was greatly strengthened when studies of migrant populations from low-risk areas to high-risk areas frequently showed dramatic increases in cancer incidence, suggesting that environment and lifestyle, not genetics, plays the major role in the origins of most common cancers (1618). Variations in dietary patterns and the intake of specific nutrients were among the factors most frequently found to change in migrant populations experiencing increases in several malignancies, especially those of the gastrointestinal tract, breast, and prostate (6-10). The continuing refinement of food-frequency questionnaires for the assessment of individual food selection and consumption patterns has led to the rapid proliferation of case-control studies and several large prospective cohort studies that are providing important data concerning diet, nutrition, and cancer risk (7,19). As we move toward the end of the century, several national and international organizations have prepared diet and nutritional guidelines for the prevention of cancer, based upon the accumulated fund of knowledge (7,20,21). In contrast to the public health approach, investigators are beginning to target high-risk subgroups for rigorous intervention studies, based upon nutrition and chemoprevention (22,23). Most investigators agree that the field of nutrition and cancer is only beginning to mature. New investigators are trained within the area of nutrition and cancer to extend knowledge via diverse studies, ranging from epidemiology to molecular biology. Although many associations between diet and cancer risk have been described, the mechanisms that underlay these relationships are typically unknown. The critical role of tumor angiogenesis in the cancer cascade suggests that these processes may be a target for diet and nutritional interventions.

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