A trawl through the current nutrition literature

Abstract

There seems little doubt that it has become exceedingly difficult in recent years for expert groups to agree on the form and content of their recommendations concerning dietary requirements of nutrients. In the United States the responsible bodies are the Food and Nutrition Board, the Institute of Medicine, and the National academies in Washington, DC. On previous occasions a single monograph covered all micro- and macronutrients at the same time. The Institute of Medicine is in the process of publishing a series of documents, five of which have been published in recent years and several more are promised in the near future.1‐5 It might be easy to miss one or more of them. Things are made much more complicated this time by major changes in terminology. The familiar recommended dietary allowance(RDA) is not being used in a general sense but has been retained for specific use; in an overall sense, RDA has been replaced by the dietary reference intake. Another complicating feature is the use of four kinds of dietary reference intake: RDA, adequate intake, tolerable upper-intake level, and estimated average requirement. RDA and adequate intake are mutually exclusive. RDA is defined as “the average daily dietary intake level that is sufficient to meet the nutrient requirement of nearly all (97‐98%) healthy individuals in a particular life stage and gender group.” Adequate intake is “a recommended intake value based on observed or experimentally determined approximations or estimates of nutrient intake by a group (or groups) of healthy people that are assumed to be adequate— used when a RDA cannot be determined.” The tolerable upperintake level is self-explanatory: “the highest level of daily nutrient that is likely to pose no risk of adverse health effects for almost all individuals in the general population.” Estimated average requirement is “a daily nutrient intake value that is estimated to meet the requirement of half of the healthy individuals in a life stage and gender group.” The estimated average requirement is used “to examine the probability that usual intake is inadequate” for an individual and “to estimate the prevalence of inadequate intakes within a group” for a group. The grouping of nutrients in particular documents is quite unhelpful. Selections of some vitamins and minerals are mixed together. Vitamin A and carotenoids are found in different documents. Close examination of the text for a particular nutrient of interest, vitamin A in my case, shows a number of inadequacies and suggests that these are widespread. In Table 5 in the review by Trumbo et al.,6 under adverse effects for vitamin A, only terato