Low levels of 25-hydroxyvitamin D are associated with a number of detrimental health effects. These include immune dysfunction, cardiovascular disease, cancer and mood disorders. Blood levels of 25-hydroxyvitamin D are directly related to the dietary intake of vitamin D, or the amount of sun exposure, which is also a source of vitamin D. Studies have investigated the effects of high doses of vitamin D supplements on the mood of individuals with low levels of 25-hydroxyvitamin D. In particular, the researchers were interested in the effects of the vitamin D on depression and anxiety. The subjects received 40,000 IU of vitamin D per week (equivalent to 5714 IU per day) for 6 months. The results of the study showed that subjects with the lowest level of 25-hydroxyvitamin D at the start of the study had a significantly greater risk of depression. However, the vitamin D supplements did not improve the mood of the subjects over the course of the study compared to the placebo, suggesting the supplement was not effective.
It is unclear why vitamin D supplements were not effective at improving the mood of the subjects compared to a placebo, particularly as the supplements were effective at raising blood levels of vitamin 25-hydroxyvitamin D. More studies will be needed to investigate possible confounding variables and to determine if vitamin D supplements are beneficial to mood. Certainly sunlight does appear to elevate both mood and vitamin D status, suggesting that perhaps the sun is a better source of vitamin D than the diet.
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