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DRI DIETARY REFERENCE INTAKES FOR Vitamin C, Vitamin E, Selenium, and Carotenoids
individuals, it prompted the suggestion that impaired intestinal absorption may be an important causative factor in low blood concentrations of vitamin C in the elderly.
However, other studies, both cross-sectional and longitudinal, of apparently healthy, well-nourished elderly populations in the United States have not found evidence of a greater incidence of vitamin C deficiency among the elderly compared to young adults and no decrease in plasma ascorbate with advancing age (Garry et al., 1982, 1987; Jacob et al., 1988). Measurement of plasma, leukocyte, and urine ascorbate concentrations in a series of studies in elderly and young men and women showed no differences due to age (Blanchard, 1991a; Blanchard et al., 1989, 1990a,b). These studies included pharmacokinetic measures related to vitamin C absorption, depletion, repletion, and renal clearance. Consistent with these findings, a later study that measured maximal renal tubular reabsorption and excretion thresholds of ascorbic acid in apparently healthy elderly and young adults found no differences in renal handling of the vitamin between the two groups (Oreopoulos et al., 1993).
Older age groups, both men and women, have decreased lean body mass compared to younger individuals and thus, potentially a lower requirement for vitamin C. However, the vitamin C requirement of the elderly may be increased due to the oxidative stress of inflammatory and infectious conditions often found in this population (Cheng et al., 1985). As previously discussed, older adults have similar or lower plasma ascorbate concentrations than young adults. Therefore, the estimated requirement for vitamin C for individuals 51 years and older will remain the same as that of the younger adult.
Vitamin C EAR and RDA Summary, Ages 51 Years and Older
In summary, no consistent differences in the absorption or metabolism of ascorbic acid due to aging have been demonstrated at median vitamin C intakes. This suggests that the reports of low blood vitamin C concentrations in elderly populations may be due to poor dietary intakes, chronic disease or debilitation, or other factors, rather than an effect of aging per se. Therefore, for the older adults, no additional vitamin C allowance beyond that of younger adults is warranted.