Vitamin requirements: an updated review

Nutrition Research Newsletter, July-August, 1993

In this major review in the American Journal of Clinical Nutrition, Robert M Russell of the USDA Human Nutrition Research Center on Aging at Tufts University, Boston, and Paolo M Suter of University Hospital, Zurich, discuss recent literature on the vitamin requirements of elderly people. The review is an update of a similar article published in 1987.

Since 1987, the body of knowledge in the area of vitamins and aging has "increased hugely." A new set of US Recommended Dietary Allowances (RDAs) has also been published. "Although the 1989 edition of the RDAs still combines all older adults into a [greater than or equal to 51-year-old age category, we believe it will be the last edition to do so. Nutritional and dietary knowledge of elderly people has expanded enough in the last decade to justify RDAs for 50-70 and [greater than or equal to]70-year-old categories, at least for several vitamins."

Vitamin A: No change was made in the RDAs for vitamin A in 1989 (1000 [mu]g RE for men, 800 for women). Results from a major European survey indicate that the current RDAs are more than ample. Concerns have been raised that the margin of safety for preformed vitamin A intake may be reduced in older people. The current RDAs do not take into account possible disease-preventing effects of [beta]-carotene and other carotenoids. "For preventing vitamin A deficiency in elderly people, the present RDAs are more than adequate and in our opinion are set too high."

Vitamin D: No change was made in the RDAs for vitamin D in 1989 (15 [mu]g/day for both men and women). Many age-related changes in vitamin D synthesis and metabolism have been reported. The present RDA for vitamin D is too low to maintain steady serum parathyroid hormone concentrations and bone health. Elderly people who are not exposed to sunlight should receive a low-dose vitamin D supplement (10 [mu]g/day).

Thiamin: No change was made in the RDAs for thiamin in 1989 (10 mg [alpha]-tocopherol equivalents for men and 8 for women). Thiamin deficiency is prevalent in some elderly populations, particularly among institutionalized or poor people. However, the deficiency is due primarily to poor intake rather than increased need. The 1989 RDAs for thiamin appear to be appropriate for elderly people.

Riboflavin: No change was made in the RDAs for riboflavin in 1989. A graded repletion study has shown that the riboflavin requirements of elderly people are only slightly lower than the current RDAs. Exercise may cause additional loss of riboflavin in elderly people. The RDAs for riboflavin for older adults " appear to have little margin for error and probably should be raised to the amounts recommended for younger adults [1.7 mg/day for men and 1.3 for women]."

Vitamin [B.sub.6]: The 1989 RDA committee reduced the vitamin [B.sub.6] RDA for older adults from 2.2 to 2.0 mg for men and from 2.0 to 1.6 mg for women. This change was inappropriate. There is substantial evidence indicating that vitamin [B.sub.6] requirements are affected by age, and the current RDAs probably do not meet the vitamin B6 needs of practically all healthy elderly people.

Vitamin [B.sub.12]: The 1989 RDA committee reduced the vitamin [B.sub.12] RDA for older adults from 3.0 to 2.0 [mu]g for men and from 3.0 to 1.6 [mu]g for women. This change "seems imprudent." Currently, there is concern about how to define the lower limit of the normal range for blood vitamin [B.sub.12] levels. Elderly patients may have neuropsychiatric disorders caused by vitamin [B.sub.12] deficiency even though they are not anemic and have blood vitamin [B.sub.12] concentrations in the "normal" range. Elderly people have a high prevalence of atrophic gastritis, a condition that can affect vitamin [B.sub.12] Metabolism. Until more data are available, an RDA of 3.0 [mu]g would be safer than the current lower values.

Folate: In their earlier review of the literature in 1987, the authors stated that the 1980 RDA for folate could be lowered without any risk of increasing the prevalence of folate deficiency among the elderly. The 1989 RDA committee did lower the folate RDA for older adults, from 400 [mu]g to 200 [mu]g for men and 180 [mu]g for women. The reviewers believe that the new RDAs, for folate are appropriate.

Vitamin C: No change was made in the RDAs for vitamin C in 1989, set at 60 mg/day for men and women. Epidemiologic evidence is beginning to suggest that high vitamin C intakes may be associated with reduced risks of senile cataract and certain cancers and may be linked with higher levels of high-density-lipoprotein cholesterol. However, it has not yet been established whether specific disease processes can be prevented or modified by amounts of vitamin C achievable through normal diets. "Until such evidence is at hand, there are no strong arguments to change the present RDAs for vitamin C."

Other Vitamins: The data are insufficient to make any statements about the requirement for vitamin K in elderly people. The current RDA for niacin appears to be justified. No new information is available on pantothenic acid or biotin.