Skin Color Change in Caucasian Postmenopausal Women Predicts Summer-Winter Change in 25-Hydroxyvitamin D: Findings from the ANSAViD Cohort Study

Context: UV radiation is responsible for vitamin D synthesis and skin tanning. Longitudinal data relating skin color to vitamin D status are lacking. Objective: Our objective was to determine whether seasonal facial skin color changes are related to changes in 25-hydroxyvitamin D [25(OH) D]. Design and Setting: We conducted a prospective observational cohort study (Aberdeen Nutrition Sunlight and Vitamin D) with five visits over 15 months, starting spring 2006 with an additional visit in spring 2008 at a university medical research center in Scotland, 57 degrees N. Participants: Participants included 314 Caucasian postmenopausal women, age 60-65 yr. Main Outcome Measures: Facial skin color was assessed by skin reflectance and expressed as the individual typology angle (ITA) (higher number indicates paler skin). 25(OH) D was measured by immunoassay. Results: Most women (43%) reported Fitzpatrick skin type III (always burns, always tans), 32% type II, and 25% type I (always burns, never tans). Overall, mean (SD) ITA in degrees were 36.6 (7.7), 38.2 (6.5), and 42.8 (5.3), respectively, for summer, autumn, and winter (P < 0.001). Linear regression showed that a 5 degrees summer-winter change in ITA, was associated with a 15 nmol/liter change in 25(OH) D (P < 0.001) but did not predict winter 25(OH)D. Reported sunscreen use was associated with higher 25(OH) D. Mean (SD) 25(OH) D (nanomoles per liter) but not skin color was lower for the top body mass index quartile (Q4) compared with the other quartiles (summer: Q1, 57.1(19.9); Q4, 49.7 (20.4); P = 0.010). Conclusions: Skin color change between summer and winter predicts seasonal 25(OH) D change. Low vitamin D status in obese women was not due to reduced sun exposure, suggesting that increased requirements or inaccessibility of vitamin D stores may be responsible. (J Clin Endocrinol Metab 96: 1677-1686, 2011)