80 percent of vitamin D from sun rather than from food
Sunlight and dietary contributions to the seasonal vitamin D status of cohorts of healthy postmenopausal women living at northerly latitudes: a major cause for concern?
Osteoporos Int () (2010)
H M Macdonald, A Mavroeidi, W D Fraser, A L Darling, A J Black, L Aucott, F O'Neill, K Hart, J L Berry, S A Lanham-New and D M Reid
University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK, h.macdonald@abdn.ac.uk.
We assessed sunlight and dietary contributions to vitamin D status in British postmenopausal women. Our true longitudinal 25-hydroxyvitamin D (25(OH)D) measurements varied seasonally, being lower in the north compared to the south and lower in Asian women. Sunlight exposure in summer and spring provided 80% total annual intake of vitamin D.
INTRODUCTION: Vitamin D deficiency is highlighted as a potential problem for countries at high latitude, but there are few true longitudinal, seasonal data to allow regional comparisons. We aimed to directly compare seasonal variation in vitamin D status (25(OH)D) in postmenopausal women at two northerly latitudes and to assess the relative contributions of sunlight exposure and diet.
METHODS: Vitamin D status was assessed in 518 postmenopausal women (age 55-70 years) in a two-centre cohort study with serum collected at fixed three-monthly intervals from summer 2006 for immunoassay measurement of 25(OH)D and parathyroid hormone. At 57° N (Aberdeen, Scotland, UK), there were 338 Caucasian women; at 51° N (Surrey, South of England, UK), there were 144 Caucasian women and 35 Asian women. UVB exposure (polysulphone film badges) and dietary vitamin D intakes (food diaries) were also estimated.
RESULTS: Caucasian women had lower 25(OH)D (p?80% total annual intake.**
CONCLUSIONS: These longitudinal data show significant regional and ethnic differences in UVB exposure and vitamin D status for postmenopausal women at northerly latitudes. The numbers of women who are vitamin D deficient is a major concern and public health problem. DOI: 10.1007/s00198-010-1467-z * PMID: 21085934