On the other side of the coin, Vitamin D has been shown to lower the secretion of melatonin which theoretically interferes with sleep. This is a small study but is noteworthy: https://www.ncbi.nlm.nih.gov/pubmed/23665342
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On the other side of the coin, Vitamin D has been shown to lower the secretion of melatonin which theoretically interferes with sleep. This is a small study but is noteworthy: https://www.ncbi.nlm.nih.gov/pubmed/23665342