Vitamin D and Depressive Symptoms in Women During the Winter: A Pilot Study
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Background: More than half of all women do not meet daily vitamin D nutrient intake recommendations, and research indicates that vitamin D supplementation during the winter may decrease depressive symptoms. Objectives: To examine the relationship of vitamin D supplementation and depressive symptoms in women living in a northern climate during the winter months. Method: In a quasi-experimental pilot study, nine women with serum vitamin D levels (as measured by 25 OR vitamin D) below 40 nanograms/milliliter (ng/mL) were administered the Beck Depression Inventory II (BDI-II). After eight weeks of vitamin D3 supplementation, six of these women completed the BDI-II and had their serum 25 OR vitamin D levels re-assessed. Results: The baseline and follow-up mean 25 OR vitamin D levels for the sub sample of six women were 21.8 ng/mL (SD = 8.33, range = 14-37) and 48.2 (SD=20.01, range 29-84) respectively (t = -4.11, p = .009). The baseline and follow-up mean BDI-II scores were 31.8 (SD = 4.79, range = 26-40) and 21.2 (SD = 11.07, range = 8-37) respectively (t = 3.37, p = .02). Vitamin D supplementation was associated with an increase in the serum D levels by an average of about 27 ng/mL, and was associated with a decline (demonstrating a negative correlation) in the BDI-II scores of an average of about 10 points. Vitamin D levels above 40 ng/mL at the end of the study were associated with BDI-II scores of 14 or less, a level indicative of minimal depressive symptoms. Discussion: This pilot study suggests that supplenlental vitamin D3 improves serum 25 OR vitamin D levels and reduces depressive symptoms. Adequately powered clinical trials are needed to better evaluate these relationships.