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

Vitamin D Life

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

See also Vitamin D Life

Noontime sun and D category starts with

Noontime sun and D has 301 items

see also
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Overview UV and vitamin D
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Which Is Worse - Avoiding Sunlight or Vitamin D Deficiency – April 2019
Have We Gotten Sunscreen Totally Wrong - Jan 2019
The Greatest Public Health Mistake of the 20th Century (sunscreen block Vitamin D) - 2017
Sunshine provides more than Vitamin D
5 Amazing Properties of Sunlight You've Never Heard About
Vitamin D and Sun conference – Germany June 2017
Embrace the Sun – benefits of the sun throughout the day and year – book June 2018

PDF is available free at Sci-Hub   10.21873/anticanres.12336

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 at uks.eu.

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.

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.

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.

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.

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