Dietary guidelines: The shape of things to come

Abstract

In his forward to the report by the American Society for Clinical Nutrition on Evidence Relating Six Dietary Factors to the Nation's Health, Assistant Secretary for Health and Surgeon General Julius Richmond brought the reason for this report and the types of government action that would be expected to follow into clear focus. He said: Individuals have the right to make informed choices and the government has the responsibility to provide the best data for making good dietary (1). This same thrust of governmental responsibility for helping the American people making prudent dietary decisions was also the focus for the Nutritional Components of the Surgeon General's report on Prevention (2), issued by Secretary Califano and Surgeon General Richmond in July 1979. In its approach to the problems of diet and disease, the panel of the American Society for Clinical Nutrition developed an important approach to a systematic analysis of the data (3). For each of the consensus papers which it delivered, this panel focused on several questions about the kinds of information which could be used to analyze the problem in hand. These included: 1 The kinds of evidence relating the nutrient in question to a specifiC disease 2 The quality and strength of this evidence favoring this relationship 3 The risks and benefits of reducing the intake of the given dietary constituent. Three kinds of evidence were evaluated. The fust came from epidemiological studies in which populations were compared. The second kind of evidence was from animal experiments; and the third kind, from human controlled studies. Several criteria for the quality of this data were examined in each of the reports presented. The consistency of the data among various population groups was regularly examined. The consistency among individuals within a given population was also evaluated. The quality of autopsy data, if available, was reviewed, and the strength of the various correlations was analyzed. What kinds of correlations were there? Was the association between a dietary event and the disease an independent one, or were there other associations which might account for the observed differences? What was the temporal association between dietary factors and the occurrence of the disease? What was the effect of a new exposure to the dietary factor? Did removal of the dietary event make a difference in the disease incidence? Were there any animal models which help in explaining the data? Was there an available biological explanation for it? Finally, the risks of removing dietary components on the population were discussed and reviewed.