The aging process as a modifier of metabolism.

Because elderly adults have distinct metabolic characteristics that alter various nutrient requirements, simple extrapolations of nutrient requirements for younger adults are not warranted. Gastrointestinal function is well preserved with aging regarding the digestion and absorption of macronutrients, but the aging gastrointestinal tract becomes less efficient in absorbing vitamin B-12, vitamin D, and calcium. The new dietary reference intakes considered recent studies in aging adults and concluded that the recommended dietary allowances (RDAs) should be 1200 mg and 15 microg for calcium and vitamin D, respectively, for persons over the age of 70 y. The new RDAs for riboflavin, niacin, thiamine, folate, vitamin B-6, and vitamin B-12 are not different for persons in the oldest age category (>70 y) than for those aged 51-70 y. Because this is a quickly advancing field, it will be important to closely follow new research on nutrient requirements and aging over the next several years.