Evidence-based nutrition

Abstract

What are the objectives of an ideal diet? Are they to prolong life or maximize quality adjusted life expectancy? Does this focus on individuals or on the population at large, taking equity and resources into account? What about externalities that should take into account cultural heritage, protection of the environment and macroeconomic considerations? Few people have the experience, expertise and knowledge to adequately address these questions. It is only feasible to argue that there are two approaches in order to establish the proper diet, with the limited objective of longevity. Contrary to the assertions of several influential groups, there is no such thing as a 'positive health', and longevity can only be defined as the inverse of mortality from all causes. The crucial questions are: do we need to study the proper diet to reduce incidence of and mortality from particular common diseases and then find the common elements in these various diets in order to construct de novo the ideal diet (bottom up approach)? Alternatively, is it better to harvest the experience of various cultures whose diets appear to protect against premature morbidity and mortality (top down approach)? The first approach would rely on associations between food groups, foods and nutrients on the one hand and the incidence of specific diseases on the other, whereas the second would evaluate and quantify the effects of 'natural' diets on longevity. The first approach has been largely followed by mainstream nutritional epidemiologists, whereas the second has been advocated by a few international experts.