Vitamin D and Mood

Many people, especially those living in colder climates, can relate to the experience of feeling blue during the winter months, when the days are short and the sun is hiding behind rain clouds. It makes sense that this experience can be attributed, in part, to less exposure to the sunshine vitamin, vitamin D[1], but there is also some research that suggests a relationship between low vitamin D and depression that isn’t related to the seasons.[2],[3] While vitamin D has many functions in the body, from immune support to bone health, this article will focus on how vitamin D levels influence mood.

Vitamin D is unusual because it requires sunlight to be activated, and food sources are not plentiful. Vitamin D is naturally found in salmon, sardines, tuna, eggs, and shiitake mushrooms. In addition, it is often added to fortified milk, and can be taken as an oral supplement. Even though the food sources listed are commonly consumed, people living in Canada, likely have low vitamin D levels, unless they are supplementing. The weather isn’t warm enough for long enough, to get adequate skin exposure to sunlight.[4] This is especially true for people of colour, as melanin tempers vitamin D absorption.[5]

It is fascinating that the UVB rays from sunlight stimulate the production of vitamin D precursors in the skin, which then undergo chemical reactions in the liver and kidneys, respectively, to become the active vitamin D. The active vitamin circulates through the bloodstream, where it can exert its various effects on the body. Receptors for vitamin D have been found in the human brain, which suggest that vitamin D plays in a role in brain functioning.[6] The fact that vitamin D is active in the brain helps to explain its role in seasonal affective disorder (SAD) and depression. SAD is considered under the umbrella of depressive disorders, but it follows a typical seasonal pattern. While depression and SAD would present with similar symptoms, SAD worsens in the fall and winter and improves in the spring and summer.

Intuitively, it makes sense that low vitamin D would be found in those with SAD, and in fact, this is supported by research. A number of studies have found lower vitamin D levels in those struggling with SAD.[7], [8] There are likely other factors present besides just low vitamin D, as not everyone who is at risk of deficiency struggles with SAD, but supplementation remains a potential treatment option to help alleviate the winter blues. The same finding was noticed in studies on the relationship between vitamin D and depression. One study evaluated for depression using self-reports and diagnostic interviews in older adults, and found that those with depression had lower vitamin D levels.[9] Another study that examined a population of young women, living in the Pacific Northwest, had similar findings.[10] In addition, this study found that higher levels of vitamin D in the fall, explained lower levels of depressive symptoms, which gives credence to the assertion that SAD is related to low vitamin D.[11]

So far, the studies mentioned have explored whether low vitamin D status is related to low mood. The next step is to understand whether supplementing with vitamin D actually improves symptoms of depression. One study examined the effect of vitamin D supplementation in those with diagnosed major depressive disorder, and found that supplementation daily over an 8-week period was associated with improved symptoms of depression.[12] Another study gave vitamin D injections to people with depression and low vitamin D, and found improvement in depressive symptoms following correction of vitamin D deficiency.[13] While these findings are encouraging, vitamin D alone may not be able to give someone enough relief from depression; however, one study found that in people with major depressive disorder, vitamin D given with the anti-depressant medication fluoxetine had better results when compared to just fluoxetine alone.[14]

In conclusion, there is evidence that supports the idea that low vitamin D is related to depression, and correcting the deficiency improves symptoms of depression. Vitamin D levels can be tested in the blood, and naturopathic doctors are able to requisition this blood work. Knowing your vitamin D level can help ascertain appropriate vitamin D dosing, and establish parameters for monitoring levels as you supplement, to insure that you are always taking a safe dose. It may be prudent to supplement until you achieve an optimal level of vitamin D, and then maintain that level through food and safe sun exposure. It is important to realize that vitamin D deficiency is just one potential contributing factor to low mood. If supplementing with this vitamin does not noticeably improve your symptoms, further investigation and additional treatment interventions are warranted.  

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[1] Melrose S. Seasonal affective disorder: an overview of assessment and treatment approaches. Depress Res Treat. 2015.

[2] Witte J. G. et al. Depression is associated with decreased 25-hydroxyvitamin D and increased parathyroid hormone levels in older adults. Arch Gen Psychiatry. 65 (5): 508-512. 2008.

[3] Kerr D. C. R. Associations between vitamin D levels and depressive symptoms in healthy young adult women. Psychiatry Res. 227 (1): 46-51. 2015.

[4] Nair R. et al. Vitamin D: the “sunshine” vitamin. J Pharmacol Pharmacother. 3(2): 118-126. 2012.

[5] Stewart A. E. Possible contributions of skin pigmentation and vitamin D in a polyfactorial model of seasonal affective disorder. Medical Hypotheses. 83 (5): 517-525. 2014.

[6] Eyles D. W. et al. Distribution of the vitamin D receptor and 1a-hydroxylase in human brain. Journal of Chemical Neuroanatomy. 29(1): 21-30. 2005.

[7] Melrose S. Seasonal affective disorder: an overview of assessment and treatment approaches. Depress Res Treat. 2015.

[8] Stewart A. E. Possible contributions of skin pigmentation and vitamin D in a polyfactorial model of seasonal affective disorder. Medical Hypotheses. 83 (5): 517-525. 2014.

[9] Witte J. G. et al. Depression is associated with decreased 25-hydroxyvitamin D and increased parathyroid hormone levels in older adults. Arch Gen Psychiatry. 65 (5): 508-512. 2008.

[10] Kerr D. C. R. Associations between vitamin D levels and depressive symptoms in healthy young adult women. Psychiatry Res. 227 (1): 46-51. 2015.

[11] Ibid.

[12] Sepehrmanesh Z. et al. Vitamin D supplementation affects the Beck Depression Inventory, insulin resistance, and biomarkers of oxidative stress in patients with major depressive disorder: a randomized controlled clinical trial. The Journal of Nutrition. 146(2): 243-248, 2016.

[13] Mozaffari-Khosravi H. et al. The effect of 2 different single injections of high dose vitamin D on improving the depression in depressed patients with vitamin D deficiency: a randomized control trial. Journal of Clinical Psychopharmacology. 33 (3): 378-385, 2013.

[14] Khoraminya N. et al. Therapeutic effects of vitamin D as adjunctive therapy to fluoxetine in patients with major depressive disorder. Australian and New Zealand Journal of Psychiatry. 47(3): 271-275, 2012.