Recently, a colleague asked me a handful of questions regarding BLT. I thought I would share my response.
Has there been any research on Vitamin D deficiency and SAD? It seems that depression is such a common diagnosis, and now Vitamin D deficiency is also being recognized as a widespread problem. I'm just wondering if there is an association between lack of sunlight leading to Vitamin D deficiency and SAD? What do you think?
There is definitely a connection between lack of sunlight and vitamin D deficiency. Vitamin D is produced by sunlight touching bare skin and converting 7-dehydrocholesterol (provitamin-D3) to cholecalciferol (vitamin D3). For the most part, it has been shown that lower vitamin D levels are found in people with depression. In general, however, vitamin D supplementation has not shown to be effective in treating depression. The pathophysiology of SAD is not fully understood; however, it is recognized that those with SAD tend to have deficient levels of vitamin D.
At first, it seems that Vitamin D and BLT would be closely related because the production of vitamin D requires sun-to-skin exposure. Actually, vitamin D requires exposure to ultraviolet wavelengths and BLT normally uses light which filters out ultraviolet light.
Interestingly, I have read one article comparing BLT to vitamin D supplementation. This study actually used a light box which included ultraviolet wave lengths (280-320nm) that are needed for the skin to produce vitamin D. This study found that the group receiving vitamin de supplementation (100,000 ID/day) actually reported lower depression than the group receiving BLT. Of note, this is the only study I have found with these results and the BLT group was only receiving 2,500 lux light (as compared to the recommended 10,000 lux). Also, the vitamin D group was receiving 100,000 IU which is a lot more than the recommended 4,000 IU.
In sum, I think that there is a connection between vitamin D and SAD... whether that be through modulation of the sleep-wake cycle or due to a direction connection between vitamin D and depression. My understanding is that vitamin D supplementation is not an adequate treatment for depression, although I think it should always be an option for patients with milder depression who might be interested in a naturopathic modality.