Vitamin D-binding protein, vitamin D status and serum bioavailable 25(OH)D of young Asian Indian males working in outdoor and indoor environments.
J Bone Miner Metab. 2017 Mar;35(2):177-184. doi: 10.1007/s00774-016-0739-x. Epub 2016 Jan 30.
Goswami R1, Saha S2, Sreenivas V3, Singh N4, Lakshmy R5.
Study of New Delhi workers in Aug-Sept
VitaminDWiki suspects that the men had dark skins and wore t-shirts or regular shirts
More vitamin D per hour can be expected if:
- Lighter skin
- Less clothing (see life-guards)
- Less air pollution
- Only consider hours in the middle of the day
(when there is UVB to make Vitamin D)
Suspect indoor workers could also get a similar level of Vitamin D if one of the following
- Take a 30 minute sunbreak daily at lunchtime while wearing a |shirt which passes 50% of the UVB rays
(Do not start with full 30 minutes in the summer - which will cause sunbrun - start slowly)
- Take a Vitamin D supplement - pehaps just one capsule every 2 weeks
Urban Asian Indians generally have low serum 25(OH)D. Information on serum bioavailable 25(OH)D and the effect of prolonged sun-exposure in them is not known. We assessed serum 25(OH)D and bioavailable 25(OH)D in males with varying durations of sun-exposure in Delhi during August-September. Serum 25(OH)D, vitamin D-binding protein (DBP), bioavailable 25(OH)D, free 25(OH)D index, iPTH, ionized calcium and sun-index were assessed in
- mixed outdoor-indoor and
- indoor workers (n = 88, 32 and 74, respectively).
The mean sun-index (12.0 ± 6.25, 4.3 ± 2.20 and 0.7 ± 0.62, respectively; P < 0.001) was highest outdoors and lowest indoors. Serum 25(OH)D (29.0 ± 8.61, 19.1 ± 5.73 and 10.9 ± 4.19 ng/ml, respectively; P < 0.001), bioavailable 25(OH)D and free 25(OH)D index were maximum in outdoor workers followed by mixed-exposure and indoor workers.
Their mean serum DBP levels (241.2 ± 88.77, 239.3 ± 83.40 and 216.6 ± 63.93 µg/ml, respectively; P = 0.12) were comparable.
Mean serum iPTH was significantly lower in outdoor than indoor workers and showed inverse correlations with serum 25(OH)D, bioavailable 25(OH)D and free 25(OH)D index (r = -0.401, -0.269 and -0.236, respectively; P < 0.001 in all).
Daily dietary-calorie intake was higher and calcium lower in outdoor than indoor workers.
On regression analysis, sun-exposure was the only significant variable, increasing serum 25(OH)D by 2.03 ng/ml per hour of sun-exposure (95 % confidence interval 1.77-2.28; P < 0.001). Outdoor workers with prolonged sun-exposure were vitamin D-sufficient, with higher serum bioavailable 25(OH)D than the indoor workers during summer. Use of serum DBP levels did not affect the interpretation of their vitamin D status.
PMID: 26832389 DOI: 10.1007/s00774-016-0739-x