Effects of Above Average Summer Sun Exposure on Serum 25-Hydroxyvitamin D and Calcium Absorption
Open Access
- 1 November 2002
- journal article
- other
- Published by The Endocrine Society in Journal of Clinical Endocrinology & Metabolism
- Vol. 87 (11), 4952-4956
- https://doi.org/10.1210/jc.2002-020636
Abstract
The purpose of this study was to examine the effects of summer sun exposure on serum 25-hydroxyvitamin D [25(OH)D], calcium absorption fraction, and urinary calcium excretion. Subjects were 30 healthy men who had just completed a summer season of extended outdoor activity (e.g. landscaping, construction work, farming, or recreation). Twenty-six subjects completed both visits: after summer sun exposure and again approximately 175 d later, after winter sun deprivation. We characterized each subject’s sun exposure by locale, schedule, and usual attire. At both visits we measured serum 25(OH)D, fasting urinary calcium to creatinine ratio, and calcium absorption fraction. Median serum 25(OH)D decreased from 122 nmol/liter in late summer to 74 nmol/liter in late winter. The median seasonal difference of 49 nmol/liter (interquartile range, 29–67) was highly significant (P < 0.0001). However, we found only a trivial, nonsignificant seasonal difference in calcium absorption fraction and no change in fasting urinary calcium to creatinine ratio. Findings from earlier work indicate that our subjects’ sun exposure was equivalent in 25(OH)D production to extended oral dosing with 70 μg/d vitamin D3 (interquartile range, 41–96) or, equivalently, 2800 IU/d (interquartile range, 1640–3840). Despite this input, at the late winter visit, 25(OH)D was less than 50 nmol/liter in 3 subjects and less than 75 nmol/liter in 15 subjects.Keywords
This publication has 18 references indexed in Scilit:
- Plasma calcidiol, season, and serum parathyroid hormone concentrations in healthy elderly men and womenThe American Journal of Clinical Nutrition, 1997
- Environmental factors that influence the cutaneous production of vitamin DThe American Journal of Clinical Nutrition, 1995
- Elderly women in northern New England exhibit seasonal changes in bone mineral density and calciotropic hormonesBone and Mineral, 1994
- Seasonal variation in bone metabolism in young healthy subjectsCalcified Tissue International, 1991
- Calcium absorption in women: Relationships to Calcium intake, Estrogen status, and ageJournal of Bone and Mineral Research, 1989
- Influence of Season and Latitude on the Cutaneous Synthesis of Vitamin D3: Exposure to Winter Sunlight in Boston and Edmonton Will Not Promote Vitamin D3Synthesis in Human Skin*Journal of Clinical Endocrinology & Metabolism, 1988
- Estimating True Fractional Calcium AbsorptionAnnals of Internal Medicine, 1988
- PROPHYLAXIS AGAINST VITAMIN D DEFICIENCY IN THE ELDERLY BY REGULAR SUNLIGHT EXPOSUREAge and Ageing, 1986
- Estimation of True Calcium AbsorptionAnnals of Internal Medicine, 1985
- COMPARISON OF ORAL 25-HYDROXYCHOLECALCIFEROL, VITAMIN D, AND ULTRAVIOLET LIGHT AS DETERMINANTS OF CIRCULATING 25-HYDROXYVITAMIN DThe Lancet, 1977