Vitamin D deficiency and insufficiency in Hawaii: Levels and sources of serum vitamin D in older adults

Objective: To examine the major sources of vitamin D [25-hydroxyvitamin D (25(OH)D)] and evaluate their collective role on rates of vitamin D deficiency/insufficiency among older adults. Methods: Cross-sectional analysis of the relationship between serum 25(OH)D levels and sources of vitamin D (self-reported and objectively validated sun exposure, supplementation, food including fortified sources). Study subjects were part of the Hawaii Longitudinal Study of Personality and Health who completed a clinic visit between 55 and 65 years (M = 59.6) and food frequency questionnaire, and provided serum to assay 25(OH)D (n = 223). Results: Although mean serum 25(OH)D levels were overall sufficient (34.3 ng/ml, [SD = 10.9]), over one-third of participants (38%) had vitamin D deficiency/insufficiency (<30 ng/ml). Asians were the most likely to be insufficient and Filipinos were the least likely (43% vs. 11%, respectively). Overall, supplement use and sun exposure were both associated with higher 25(OH)D levels and lower risk of vitamin D deficiency/insufficiency. Moreover, Vitamin D sources varied by race/ethnic groups. In multivariate models, higher body mass index, being Asian or Native Hawaiian/Pacific Islander, low supplement use, and low sun exposure were associated with higher risk for vitamin D deficiency/insufficiency (<30 ng/ml). Conclusions: Over 1/3 of the older adult sample was vitamin D deficient/insufficient, despite most of the participants living in a tropical climate with year-round access to sun as a vitamin D source. Sun exposure and supplement use, but not food intake, explained differences in vitamin D deficiency/insufficiency in this population.