25(OH)D Serum levels decline with age earlier in women than in men and less efficiently prevent compensatory hyperparathyroidism in older adults.

BACKGROUND: Although a host of factors are known to influence 25-hydroxyvitamin D [25(OH)D] serum levels, few studies addressed the distinctive sex-specific influence of aging, and the age-specific relationship of parathyroid hormone (PTH) with 25(OH)D. The aims of this research were to evaluate changes of 25(OH)D and PTH levels with age in a large population-based sample of men and women and to test the hypothesis that 25(OH)D serum concentrations needed to offset age-associated hyperparathyroidism are significantly higher in older than in younger persons. METHODS: In 1107 participants of the InCHIANTI (Invecchiare in Chianti, i.e., Aging in the Chianti area) study, we collected information on dietary intake, daylight exposure, and disability, and measured renal function and serum 25(OH)D and PTH. RESULTS: In women, the age-related decline of 25(OH)D was already evident shortly after age 50, whereas in men it started only after age 70 and was substantially less steep. Age, daylight exposure, winter season, and disability were independent predictors of low 25(OH)D levels. For any given level of 25(OH)D, PTH levels were progressively and consistently higher in older than in younger participants. CONCLUSIONS: These findings suggest that the age-associated fall of serum 25(OH)D starts earlier in women than in men and that higher levels of 25(OH)D are required in older compared to younger persons to avoid the age-associated compensatory hyperparathyroidism.

Marked decrease in plasma antioxidants in aged osteoporotic women: results of a cross-sectional study.

Although recent epidemiological studies found a positive correlation between dietary vitamin C intake and bone mineral density, data on plasma levels of vitamin C or other antioxidants in osteoporotic subjects are scanty. The aim of this study was to evaluate whether antioxidant defenses are decreased in elderly osteoporotic women and, if this is the case, to understand whether osteoporosis is a condition characterized by increased oxidative stress. To answer these questions, plasma vitamins C, E, and A; uric acid; and the enzymatic activities of superoxide dismutase in plasma and erythrocytes and of glutathione peroxidase in plasma were measured in 75 subjects with osteoporosis and 75 controls. Dietary and endogenous antioxidants were consistently lower in osteoporotic than in control subjects. On the other hand, plasma levels of malondialdehyde, a byproduct of lipid peroxidation, did not differ between groups. Our results reveal that antioxidant defenses are markedly decreased in osteoporotic women. The mechanisms underlying antioxidant depletion and its relevance to the pathogenesis of osteoporosis deserve further investigation.