Insights in Nutrition and Metabolism

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Optimal cutaneous vitamin D synthesis: Balance between beneficial and harmful health effects of solar UV-B

September 15-16, 2017 | Dallas, USA

Janusz W Krzyscin

Institute of Geophysics, Poland

Scientific Tracks Abstracts : Insights Nutr Metab


Statement of the Problem: Early humans, before migration out of East Africa (~100,000 years ago), lived in surroundings abundant in solar radiation, and to this day, traditionally living Hadza people in Tanzania have vitamin D levels of ~115 nmol/L. Migration to other continents induced loss of skin pigmentation to keep the same vitamin D3 production as it was previously in East Africa. Thus, the level of 115 nmol/L could serve as the measure of optimal vitamin D status that was formed during millennia of human evolution. It represents a target for contemporary humans usually having a vitamin D deficit. Methodology & Theoretical Orientation: Krzyścin et al. (2016) modeled vitamin D doses received by the Hadza adults during typical life activities and found that the daily vitamin D3 synthesis due to solar exposures was equivalent to ~2000 IU of vitamin D3 taken orally. To assess safety of sunbathing to get such high doses by people with different skin phototypes, we propose to calculate a health risk factor (HRF), i.e. a number of the optimal vitamin D doses attained during maximal allowed duration of sunbathing yielding exposure of 1 Minimal Erythemal Dose. Findings: It appears that HRF is independent on skin phototypes. The optimal vitamin D dose is obtained safely, i.e. without erythema, for HRF>1. Such conditions usually happen around sunny noon in spring/summer for people exposing ~30% of the whole body. Conclusion & Significance: Analyses of HRF time series for several midlatitudinal sites show that young adults (~20 yr.) could obtain optimal vitamin D3 doses equivalent to 2000 IU vitamin D3 taken orally for only 2-3 months per year. Such vitamin D3 supplementation seems to be necessary over the whole year for persons >59 yr. but it may be reduced to ~1000 IU in spring/summer for outdoor active persons.


Janusz W Krzyścin has been involved in modelling surface UV radiation for almost 30 years. He has developed a model for serum 25(OH) vitamin D changes due to solar exposure and elaborated theory for antipsoriatic heliotherapy to be carried out in any country. He proposed a method of improving vitamin D3 status by using UV transparent garment made of fine linen that is especially important for persons exposing limited skin area due to cultural/religious reasons. He is a leader of team producing free smartphone apps for planning and monitoring healthy sunbathing.

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