Spring sunshine in snowy Finland normalized Vitamin D levels to 36 nanograms – 2017

Created March 2018

The effect of vernal solar UV radiation on serum 25-hydroxyvitamin D concentration depends on the baseline level: observations from a high latitude in Finland.

Int J Circumpolar Health. 2017;76(1):1272790. doi: 10.1080/22423982.2016.1272790.

Karppinen T1,2,3, Ala-Houhala M2, Ylianttila L4, Kautiainen H5,6,7, Lakkala K8, Hannula HR8, Turunen E9, Viljakainen H10, Reunala T1, Snellman E1,2.

Summary, observations and questions by Vitamin D Life* 12 hours outdoors with face and hands exposed (7% of body area)* Baseline average Vitamin D levels = 36 ng * due probably to sun, tanning bed, fatty fish, and/or supplements* UV Index varied from 1.2 to 2.7* Vitamin D levels were raised if < 36 ng* Vitamin D levels were reduce if > 36 ng1. Well known that UVB increases Vitamin D and that UVA decreases Vitamin D1. Might UVA/UVB ratio change with amount of snow reflectivity (albedo)?1. Might the 36 ng normalization level change at different times of the year?---* UVA causes skin cancer, perhaps UVB (Vitamin D) prevents skin cancer – Jan 2017* UVA decreased vitamin D levels (again) – July 2013* UVA decreased serum levels of vitamin D - RCT Oct 2012* UVB produced 8X more vitamin D as solar UV – July 2012* No UVA to decrease the levels* 2 cents of vitamin D far better than sunbathing for 30 minutes daily – Nov 2017* Suspect: 12 cents of Vitamin D would increase more than 12 hours in snowy Finland--- 1. UV and D starts with{include}

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Humans obtain vitamin D from conversion of 7-dehydrocholesterol in the skin by ultraviolet B (UVB) radiation or from dietary sources. As the radiation level is insufficient in winter, vitamin D deficiency is common at higher latitudes. We assessed whether vernal solar UVB radiation at latitudes 61°N and 67°N in Finland has an impact on serum 25-hydroxyvitamin D [S-25(OH)D] concentrations.

Twenty-seven healthy volunteers participated in outdoor activities in snow-covered terrain for 4-10 days in March or April, with their face and hands sun-exposed. The personal UVB doses and S-25(OH)D levels were monitored. A mean UVB dose of 11.8 standard erythema doses (SED) was received during an average of 12.3 outdoor hours.

The mean S-25(OH)D concentration in subjects with a baseline concentration

  • below 90.0 nmol/L (n=13) increased significantly,
    • by 6.0 nmol/L from an initial mean of 62.4 nmol/L (p<0.001),

whereas in those with a basal concentration

  • above 90.0 nmol/L (n=12) it decreased significantly,
    • by 6.7 nmol/L from a mean of 116.9 nmol/L (p<0.01).

To conclude, only 7% of total body surface area was exposed to vernal sunlight and this was capable of increasing S-25(OH)D levels in subjects with a baseline level below 90 nmol/L but not in those with higher levels.

PMID: 28452681 PMCID: PMC5328343 DOI: 10.1080/22423982.2016.1272790

Tags: Sun UV