Sunlight increases serum 25(OH) vitamin D concentration whereas 1,25(OH)2D3 is unaffected. Results from a general population study in Göteborg, Sweden (The WHO MONICA Project).

ABSTRACT

OBJECTIVE: To determine serum 25-hydroxyvitamin D3 [25(OH)D3] and its 1-hydroxylated metabolite [1,25(OH)2D3] and relate them to anthropometric data, life-style habits, blood pressure and selected biochemical analytes. DESIGN: Random population samples of men and women. SETTING: Göteborg, Sweden, population size 450,000 inhabitants. The study was performed within the framework of the WHO MONICA Project. SUBJECTS: 2000 randomly selected subjects were invited to the main MONICA screening. Out of those 1421 (71%) participated. Fifty individuals in each of four age-groups, 25-64 years, were selected at random for the present analyses (184 men and 198 women). RESULTS: The concentration of 25(OH)D3 was similar in both sexes whereas 1,25(OH)2D3 concentration was higher in women than in men (P = 0.01). 25(OH)D3 correlated positively to sun exposure, physical activity and negatively to intact parathyroid hormone (PTH) in both sexes, and also negatively to blood pressure in men. The remaining significant relationship for 25(OH)D3, when age and sun exposure were taken into account in multivariate analyses, was a negative correlation to intact PTH in both sexes. 1,25(OH)2D3 correlated positively to intact PTH in both men and women, negatively to height in men, positively to fibrinogen in men and positively to psychological stress and osteocalcin in women. When all variables were included in multivariate analyses 1,25(OH)2D3 concentration correlated negatively to age and positively to intact PTH and osteocalcin in both sexes together. CONCLUSIONS: Sunlight was the only external factor that influenced 25(OH)D3 concentration whereas 1,25(OH)2D3 was unaffected by sun exposure. 1,25(OH)2D3 was not related to environmental or life style factors but declined by age and correlated positively to intact PTH and osteocalcin. SPONSORSHIP Grants from the Swedish Medical Research Council and the Swedish Heart and Lung Foundation.