Sun Exposure, Vitamin D Intake and Vitamin D Status in Davis, CA.

Abstract

The contribution of sun exposure to vitamin D status is difficult to assess. The objective of our study was to measure the contribution of sun exposure, dietary intake and level of skin pigmentation to vitamin D status as measured by serum 25OH vitamin D (25OHD). Our study was conducted with 4 cohorts of healthy young adults each followed for 7â8 wks in the Fall, Winter, Spring and Summer (2006â07) in Davis, CA (38.55 N). Subjects had a wide range of sun‐exposure behavior and skin pigmentation. A total of 72 subjects (â¼18 per season) enrolled and completed the study. Skin pigmentation was measured using a reflectance spectrophotometer. Dietary vitamin D intake was assessed by food records. Sun exposure was assessed using UVB dosimeter badges and questionnaires. Serum 25OHD was measured by LC‐MS. Multiple linear regression analysis was used to predict serum 25OHD using continuous variables for sun exposure (UVB dosimeter), skin pigmentation and diet, and dummy variables for cohort. Sun exposure, skin pigmentation and diet were all significant predictors of serum 25OHD (p < 0.05). These results show that the contribution of these variables to vitamin D status can be assessed using simple methods in free‐living adults. These methods may help nutritionists make more accurate individualized recommendations for vitamin D intake based on skin pigmentation and sun behavior.