ABSTRACT
It is generally accepted that intakes moderately above the recommended allowances are optimal for the well-being of an organism. However, a number of studies performed on animals have demonstrated that longevity was increased when the intakes of certain nutrients were lower than the recommended allowances. Similarly, very high intakes of some nutrients have been reported to shorten life span. 1 Furthermore, little information is available regarding the influence of nutritional status at one period in life on the remaining periods. In the past, emphasis has been placed primarily on the establishment of the nutritional requirements of young growing animals. Few efforts have been made to determine whether changes occur in nutritional requirements following growth cessation. Many age changes in physiological functions may result in increased nutritional needs in later life. For example, cellular loss and decrements in biochemical systems such as active transport may impair absorption in the elderly. In addition, the greater displacement from basal levels and the slow rate of return following various challenges such as glucose administration may increase metabolic demands and, therefore, nutritional requirements. Finally, age-associated decreases in hormonal secretions may result in reduced efficiency of the metabolism of specific nutrients. Therefore, an attempt will be made to review the pertinent literature on (1) the effect of age on nutritional requirements after the cessation of growth and (2) the effect of nutrition on life span. This information may provide useful knowledge for the optimal nutrition of the aged and for an understanding of the basic mechanisms of biological aging. Studies concerned with the first problem area have been carried out principally with human subjects, whereas those concerned with the second have been performed with animals.
