Vitamin D produced by hands and face is 8X more than elsewhere

Created July 2018

The Impact of UV-dose, Body Surface Area Exposed and Other Factors on Cutaneous Vitamin D Synthesis Measured as Serum 25(OH)D Concentration: Systematic Review and Meta-analysis.

Anticancer Res. 2018 Feb;38(2):1165-1171, 10.21873/anticanres.12336

The face and hands produced 8X more vitamin D than other parts of the body     They are much more likely to have access to the sun than other parts of the body It appears that there is a limit as to how much vitamin D can be produced at a time     per hour? per portion or day?, per day?   Study does not appear to discuss questions 1) Does increase UVA decrease the amount of Vitamin D generated? 2) Does UVA actually decrease existing levels of Vitamin D? 3) Is more Vitamin D generated when starting at a low vitamin D level (Spring)? 4) Is the amount of vitamin D generated a function of amount of body cholesterol? 5) Is the amount of Vitamin D generated a function of skin temperature? 6) Why is there a range of 5X in the amount of vitamin D generated between people?     even after accounting for skin color, obesity, and initial Vitamin D levels --- 1. See also VitaminDWiki * Overview UV and vitamin D * 3.3 X more likely to be Vitamin D deficient if wear long-sleeves – Oct 2022 * UVA causes skin cancer, perhaps UVB (Vitamin D) prevents skin cancer – Jan 2017 * More UV and vitamin D, less infectious disease – Jan 2017 * Vitamin D production after UVB exposure – A comparison of exposed skin regions – Feb 2015 * Sumilar conclusion was reached by the later study on this page 1. Noontime sun and D category starts with {include} --- Cited by 27 studies as of Oct 2022

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Jager N1,2, Schöpe J1,3, Wagenpfeil S1,3, Bocionek P4, Saternus R1,2, Vogt T1,2, Reichrath J5,2.

1 Center for Clinical and Experimental Photodermatology, The Saarland University Hospital, Homburg, Germany.

2 Department of Dermatology, The Saarland University Hospital, Homburg, Germany.

3 Institute for Medical Biometry, Epidemiology and Medical Informatics, Saarland University, Homburg, Germany.

4 Jörg Wolff Foundation, Stuttgart, Germany.

5 Center for Clinical and Experimental Photodermatology, The Saarland University Hospital, Homburg, Germany Joerg.reichrath@uks.eu.

BACKGROUND/AIM:

To optimize public health campaigns concerning UV exposure, it is important to characterize factors that influence UV-induced cutaneous vitamin D production. This systematic review and meta-analysis investigated the impact of different individual and environmental factors including exposed body surface area (BSA) , UVB dose and vitamin D status, on serum 25(OH)D concentration.

MATERIALS AND METHODS:

In accordance with Preferred Reporting Items for Systematic Reviews and Meta-analyses, and Meta-analysis of Observational Studies in Epidemiology guidelines, a systematic literature search was conducted (MEDLINE; 01/1960-07/2016) investigating the impact of these factors on vitamin D status after artificial UV exposure as main outcome measure. Summary mean differences [and 95% confidence interval (CI)] were derived from random-effects meta-analysis to account for possible heterogeneity across studies. Meta-regression was conducted to account for impact of UVB dose, baseline 25(OH)D level and BSA.

RESULTS:

We identified 15 studies, with an estimated mean 25(OH)D rise per standard erythema dose (SED) of 0.19 nmol/l (95% CI 0.11-0.26 nmol/l). Results from meta-regression suggest a significant impact of UV dose and baseline 25(OH)D concentration on serum 25(OH)D level (p<0.01). Single UVB doses between 0.75 and 3 SED resulted in the highest rise of serum 25(OH)D per dose unit. BSA exposed had a smaller, non-proportional, not significant impact. Partial BSA exposure resulted in relatively higher rise compared to whole-body exposure (e.g. exposure of face and hands caused an 8-fold higher rise of serum 25(OH)D concentration/SED/1% BSA compared to whole-body exposure). Our findings support previous reports, estimating that the half-life of serum 25(OH)D varies depending on different factors.

CONCLUSION:

Our results indicate that partial BSA exposure (e.g. 10%) with moderate UV doses (e.g. 1 SED) is effective in generating or maintaining a healthy vitamin D status. However, due to limitations that include possible confounding factors such as skin type, which could not be considered, these findings should be interpreted with caution.

Tags: Sun UV