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Nutritional Requirements Throughout the Life Cycle

We all need essential amino acids, carbohydrate, essential fatty acids, and 28 vitamins and minerals to sustain life and health. However, nutritional needs vary from one life stage to another. During intrauterine development, infancy, and childhood, for example, recommended intakes of macronutrients and most micronutrients are higher relative to body size, compared with those during adulthood. In elderly persons, some nutrient needs (eg, vitamin D) increase, while others (eg, energy, iron) are reduced.

The National Academy of Sciences has published recommendations for Dietary Reference Intakes (DRI)1 that are specific for the various stages of life. It should be noted, however, that the DRIs are not designed for individuals who are either chronically ill or who are at high risk for illness due to age, genetic, or lifestyle factors (eg, smoking, alcohol intake, strenuous exercise). Clinicians must make their own judgments regarding nutrient requirements in such cases based on available information (see table).

In this chapter, we will examine nutrient needs throughout the life cycle. Two major themes emerge:

First, the predominant nutritional problem in developed countries is overnutrition. It has led to unprecedented epidemics of obesity and chronic diseases. Clinicians can assist patients in making the dietary shifts necessary to prevent overnutrition and its sequelae.

Second, a renewed emphasis on vegetables, fruits, whole grains, and legumes can help prevent weight problems and chronic illnesses, including cardiovascular disease,2 diabetes,3 and cancer,4 among others.5 Plant–based diets meet or exceed recommended intakes of most nutrients, and have the advantage of being lower in total fat, saturated fat, and cholesterol than typical American diets,6 with measurable health benefits.7


Nutritional Requirements Throughout the Life Cycle: Adolescence and Adulthood >>