Sunlight exposed body surface area is associated with serum 25-hydroxyvitamin D (25(OH)D) level in pregnant Minangkabau women, Indonesia

BACKGROUND: Vitamin D deficiency is highly prevalent in women, and living in a tropical country with a year-round abundance of sunlight as the primary source of vitamin D does not seem to guarantee adequate serum 25(OH)D. While living in the tropics, Minangkabau women are known to dress specifically according to their culture. This study was aimed to elucidate the association of sunlight exposed body surface area with serum 25(OH)D in pregnant Minangkabau women of Indonesia. METHODS: We performed a cross-sectional study on 88 Minangkabau women in late pregnancy. Lifestyle data were collected using a questionnaire, and dietary intake of vitamin D was calculated from 24-h food recall. The skin pigmentation type was determined by the Fitzpatrick scale, and the body surface area exposed to sunlight was estimated. Serum 25(OH)D was quantified by ELISA method. Serum 25(OH)D differences according to the duration of sunlight exposure, skin pigmentation type, and sunscreen use were statistically analyzed by ANOVA. The correlation of sunlight exposed body surface area and serum 25(OH)D was analyzed by Spearman’s correlation. RESULTS: Nearly half of the subjects (n = 40; 45.5%) were deficient in vitamin D (< 20 ng/ml) with serum 25(OH)D level 23.0 ± 10.0 ng/ml (mean ± SD) and the estimated daily intake of vitamin D was 5.6 ± 3.9 μg/1000 kcal/day (mean ± SD). The median percentage of body area exposed to sunlight was 15.8%. There were no differences in serum 25(OH)D levels according to sunlight exposure time, skin pigmentation type, and sunscreen use. The percentage of body area exposed to sunlight was positively correlated with serum 25(OH)D level (Spearman’s ρ = 0.403; p < 0.001). CONCLUSIONS: Vitamin D deficiency is prevalent in pregnant Minangkabau women. Since increasing body surface area exposed to sunlight may not be culturally acceptable, vitamin D supplementation needs to be considered in this population.