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Vitamin D status of older South Africans
K E Charlton1, D Labadarios, C J Lombard
1HSRC/UCT Centre for Gerontology, University of Cape Town.
Objective:
To determine the vitamin D status of older coloured' South Africans who had not sustained a fracture.
Design:
Cross-sectional analytic study.
Methods:
A random sample of 200 non-institutionalised subjects in Cape Town aged > or = 65 years was drawn using a two-stage cluster design. Trained fieldworkers interviewed subjects to obtain demographic, dietary and lifestyle data, to draw fasting blood samples for the analysis of serum 25-hydroxyvitamin D (25(OH)D) and other biochemical parameters, and to take anthropometric measurements.
Results:
Seventeen per cent of the subjects (95% CI: 11.4-22.6%) had serum 25(OH)D levels in the deficient range for the elderly (< 10 ng/ml); 7.5% (95% CI: 3.6-11.4%) had concentrations in the moderately severe range of deficiency (< 8 ng/ml). Sixty-three per cent of the subjects had raised serum alkaline phosphatase concentrations. Regression modelling showed neither a sex difference in 25(OH)D levels nor a sex-age interaction; however, a negative association with age was found (r = -0.18; P < 0.05). Mean oral vitamin D intake was low (3.6 (SD = 2.7) micrograms and 2.8 (SD = 1.7) micrograms for men and women, respectively), but no association between dietary vitamin D intake and serum 25(OH)D was found.
Conclusions:
The prevalence of suboptimal vitamin D status was high. However, the interpretation of the data, with regard to bone health, is limited by the cross-sectional design of the study. Further investigation is required to determine the potential benefits of intervention in this age group.