Nutritional Adequacy in Dietary Restriction

Abstract

An objective of long-term dietary restriction studies involving laboratory animal species is to decrease calorie or nutrient consumption without imposing energy or nutrient deficiencies. In nutritional terms, these animals are to be provided adequate nutrition to meet their maintenance requirements. Most frequently, this objective is achieved by offering test animals a fixed percentage of the amount of diet consumed by ad libitum-fed control animals. The use of this procedure has provided a considerable amount of data showing beneficial effects of dietary restriction (McCay et al. 1935; Masoro 1988; Weindruch and Walford 1988). However, this method of restricting energy or nutrient consumption, without consideration of the quantitative minimum nutrient requirements, may result in animals receiving less than adequate nutrition. Factors contributing to potential deficiencies when animals are fed at near maintenance levels are the inherent variations in dietary nutrient concentrations between production lots of a diet and difference in nutrient requirements due to genotype. The well-being of animals is at risk when their energy or nutrient consumption is below maintenance requirements, even for short periods; consequently, data collected during these periods may be compromised. The objectives of this presentation are to review the status of the nutrient requirements for maintenance of the laboratory animal species most frequently used in dietary restriction studies and to discuss procedures that may be used to insure that they receive adequate maintenance level nutrition.