As early as the 1930s, experiments on laboratory animals revealed that diet can considerably influence the process of cancer causation and development (carcinogenesis) (Tannenbaum 1942a, 1942b; Tannenbaum and Silverstone 1953). It was several decades later, however, that the first epidemiological studies appeared to indicate that diet could play a role in human cancer. A key conference held in 1975, entitled “Nutrition in the Causation of Cancer,” summarized the existing knowledge and hypotheses (Wynder, Peters, and Vivona 1975). From that moment, research in experimental systems, including animal models and epidemiological studies, increased rapidly, providing extensive information on the impact of nutritional traditions and specific macro- and micronutrients on several types of cancer. Considerable progress had already been made in several underlying sciences. For example, advances had been achieved in understanding the mechanisms of action of nutrients, the process of carcinogenesis, and the classification of carcinogens according to their mode of action (Kroes 1979;Weisburger and Williams 1991).

In particular, epidemiological studies on the international variations in incidence rates for certain cancers pointed to the existence of one or more exogenous factors that could be controlled. Observational studies had been conducted with migrants from countries with lower incidence rates to countries with higher incidence rates. A rapid increase from the lower to the higher incidence in those migrants supported the suggestion that environmental causes, and especially prevailing dietary habits, may influence the development of a number of neoplasms.