The Surprising Connection Between Vitamin D Deficiency and Depression
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In the world of vitamins, there’s one that has long basked in the radiant spotlight of sunshine. For decades, when we thought of Vitamin D, we envisioned sun-soaked days at the beach, tanning salons, and the critical prevention of rickets in children. But beneath this sun-kissed surface lies a fascinating, multifaceted story.
First some basics… Vitamin D is a fat-soluble vitamin, which means that excess amounts can be stored in the fat cells of the body and used later when the body needs it. There are not many foods that naturally contain vitamin D (oily fish, such as sardines, herring, tuna, mackerel, salmon, cod liver oil, egg yolks, shiitake mushrooms, liver or organ meats). As a result, synthesis by the skin after ultraviolet-B (UVB) radiation is the main route to obtaining vitamin D, accounting for 90% of vitamin D replenishment. 1
A common misconception is that vitamin D is absorbed straight from the sun through our skin into the body, but the process is more complicated than that. In the epidermal cells of your skin is a cholesterol-like precursor (7-dehydrocholesterol) which is converted by UVB radiation into pre-vitamin D. This pre-vitamin D is then converted into vitamin D3, which is biologically inactive. It then needs to be in its activated form via enzymes in the liver and then again through the kidneys.1 As this process is not the focus of this article, I won’t bore you with the details.
We have known for a while that severe vitamin D deficiency can cause rickets in infants or children, and osteomalacia in adults. This is because vitamin D is essential for calcium homeostasis and bone metabolism. More recent studies have found that vitamin D has associations with energy homeostasis, and the regulation of the immune and endocrine systems as well as cancer, cardiovascular disease, diabetes, autoimmune diseases, and depression.1,2,3
Severe vitamin D deficiency is no longer nearly as common as it used to be with estimates of only 13% of the European population found to be severely deficient.2 The prevalence of subclinical vitamin D deficiency in both developed and developing countries is significantly larger, with estimates of up to 1 billion individuals worldwide, where ~40% of Europeans are vitamin D deficient.2,3
There are several reasons validating the association between vitamin D and depression. These include an increased region-specific expression of vitamin D receptors in brain areas involved in mood regulation and the fact that vitamin D has neuroprotective properties (anti-inflammatory effects). Additionally, vitamin D regulates the hypothalamic-pituitary-adrenal axis, which controls the production of neurotransmitters such as epinephrine, norepinephrine, and dopamine.4, 5 A range of different studies have been done to test this association and all of them found that depressed individuals had lower levels of vitamin D compared to controls, and those individuals that had the lowest vitamin D levels had the highest risk of developing depression. 4
Upon testing the relationship between chronic kidney disease (CKD) and depression, it was found that the prevalence of depression was higher in CKD patients than in the general population and was significantly higher in CKD patients with a vitamin D deficiency. They also showed that vitamin D deficiency significant independent predictor of depression after adjusting.6 Additional research found that individuals with a vitamin D deficiency were 75% more likely to develop depression than individuals with adequate levels.5
Akpınar and others (2022) reviewed a large variety of studies testing the association between depression and vitamin D and found an inverse relationship between plasma Vitamin D and depression symptoms and major depressive disorder. It was concluded that individuals with high vitamin D levels were less likely to develop depressive symptoms/depression. 5
Although there have been many studies highlighting the association between vitamin D and depression, it is not as clear-cut as we would like it to be. There needs to be larger, more rigorous trials performed to answer the question of whether vitamin D can benefit subjects with subsyndromal depression and syndromal major depression. In other words, it needs to be determined whether vitamin D will only be able to benefit those who have symptoms of depression but are not severe enough to meet the criteria for a depression diagnosis, or whether it could also benefit those who meet the criteria to be diagnosed with depression.
More research is required before we can prescribe vitamin D to every person with depressive symptoms and it most likely will not be a cure for depression. However, there is a clear relationship between depression and vitamin D, and vitamin D plays several other important roles in the body. So, in the meantime, make sure to spend some time in the sun (safely), in your cozzie with your favourite book to ensure you are not vitamin D deficient!
- Chang SW, Lee HC. 2019.Vitamin D and health – The missing vitamin in humans. Pediatrics & Neonatology. 60(3):237–44. Available here.
- Amrein K, Scherkl M, Hoffmann M, et al. 2020. Vitamin D deficiency 2.0: An update on the current status worldwide. European Journal of Clinical Nutrition, 74(11):1–16. Available here.
- Sizar O, Khare S, Goyal A. 2022. Vitamin D deficiency. In: StatPearls. StatPearls Publishing, Treasure Island (FL). Available here.
- Menon V, Kar S, Suthar N. 2020. Vitamin D and depression: A critical appraisal of the evidence and future directions. Indian Journal of Psychological Medicine, 42(1):11. Available here.
- Akpınar Ş, Karadağ MG. 2022. Is Vitamin D important in anxiety or depression? What is the truth? Current Nutrition Reports, 13;11:675–681. Available here.
- Jhee JH, Kim H, Park S, et al. 2017. Vitamin D deficiency is significantly associated with depression in patients with chronic kidney disease. PLOS ONE, 12(2):e0171009. Available here.