Each hour of outdoor work in India increased vitamin D levels by 2 nanograms

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

Vitamin D

Outdoor 29 ng

Indoor 11 ng

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 1. 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) 1. Take a Vitamin D supplement - pehaps just one capsule every 2 weeks 1. See also VitaminDWiki * Most S. Calif lifeguards have good level of vitamin D (above 40 ng) - Aug 2016 * Little Vitamin D generated by face and hands - June 2015 * Why India's vitamin D deficiency is grim - 40 pages Feb 2014 * Indoor workers have lower vitamin D levels than outdoor workers, unless lead smelter – June 2017 * Vitamin D level of outdoor workers in India was only 18 ng– May 2019 * High levels of Vitamin D and low rates of skin cancer among commercial fishermen – July 2019 * Large variability in response to UV (more than response to oral Vitamin D) – March 2016 * Dark-skinned hunter-gatherers may generate 2,000 IU of vitamin D daily - June 2016

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

outdoor,
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