Association between quantitative measures of skin color and plasma 25-hydroxyvitamin D.
We examined the relationship between vitamin D and skin color measured by reflectance colorimetry at an exposed and un-exposed site in 321 people. Exposed but not unexposed skin color was associated with better vitamin D status. Sun-exposure was more important than natural skin color in determining vitamin D status in our population.


BACKGROUND
Vitamin D is obtained through UV synthesis in the skin where melanin limits its synthesis. Ethnicity is often used as a proxy for skin color, but skin color varies considerably. The relation between quantitative measures of skin color and plasma 25-hydroxyvitamin D (25OHD) concentration has not been well described.


METHODS
The aim of this study was to determine the association between constitutive (natural) and sun-induced skin color and 25OHD in a group of Pacific People (n = 87) and Europeans (n = 255) living in NZ (46 degrees S) in summer. Plasma 25OHD was determined and sun-induced (outer fore-arm) and constitutive (upper inner-arm) measured by reflectance colorimetry.


RESULTS
Mean (SD) 25OHD was significantly higher in Europeans than Pacific People, 88 (31) nmol/L vs. 75 (34) nmol/L, respectively. Based on constitutive skin color, 35% of participants were very light, 45% light, 16% intermediate, 4% tanned, and 0% brown or dark. Skin color at the forearm but not constitutive skin color was a significant predictor of 25OHD. Each 10 degrees lower skin color value at the forearm (more tanning) was associated with a 5 nmol/L higher 25OHD (P < 0.001).


CONCLUSIONS
Tanning but not natural skin color was an important determinant of 25OHD. Further study is needed in a population with a higher proportion of darker skin people.
Rockell
J E P
JE
Department of Human Nutrition, University of Otago, Dunedin, New Zealand.
Skeaff
C M
CM
Williams
S M
SM
Green
T J
TJ
D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D003124:Colorimetry / Q000379:methods; D012880:Skin Pigmentation / Q000502:physiology / Q000528:radiation effects; D013472:Sunlight; D055107:Suntan / Q000502:physiology; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood; D000095188:Pacific Island People; D044465:White People
C104450:25-hydroxyvitamin D; D014807:Vitamin D