Discover what emerging research tells us about the relationship between vitamin D and depression.
Vitamin D has long been known to be essential when it comes to keeping bones strong and boosting the immune system, but is there a link between vitamin D and depression? While the research findings are mixed, there’s a growing body of evidence that suggests a possible relationship between low circulating vitamin D levels in the blood and depression.
If you have depression, you’re not alone. Approximately 8.4% of U.S. adults experienced a major depressive episode in 2020, according to the National Institute for Mental Health. It can affect aspects of everyday life, from social interactions to sleep.
While treatments like talking therapies and medication are well established, the potential role of vitamin D is attracting attention. To help you understand more about the link between vitamin D and depression, we’ve sifted through the latest research to bring you everything you need to know about the role of vitamin D, the signs of vitamin D deficiency and depression, and practical steps to reach your vitamin D needs — including the best vitamin D supplement.
First, let’s get under the surface of how vitamin D works. When UV rays from the sun hit the skin, they stimulate vitamin D production. This is why it’s called the ‘sunshine vitamin’.
According to the Office of Dietary Supplements(opens in new tab), before the body can use it, vitamin D has to be activated. The liver converts it into calcidiol, which in turn becomes calcitriol in the kidneys.
“Vitamin D provides strength to bones, teeth and tissues by absorbing calcium and phosphorus in the body,” says says Sue-Ellen Anderson-Haynes(opens in new tab), registered dietitian nutritionist and national spokesperson for the Academy of Nutrition and Dietetics. “It also regulates the amount of calcium in the blood.
“Vitamin D also plays a role in the immune system. Research shows that low vitamin D levels are associated with increased infection and autoimmune disease.”
Research findings have sparked interest in the link between vitamin D and depression. “Recent studies show that low vitamin D levels are often seen in those diagnosed with clinical depression — there is an inverse relationship,” explains Anderson-Haynes.
One review, published in the British Journal of Psychiatry(opens in new tab), examined data from over 30 000 participants and found that people with depression tended to have lower vitamin D levels. While we don’t fully understand the nature of the link between vitamin D and depression, there are several possible explanations, though none have been proven.
One potential theory is that vitamin D deficiency causes depression. If that were the case, you would expect supplementation to alleviate symptoms. But studies show mixed results. One review, published in CNS Drugs(opens in new tab), found that supplementation with vitamin D eased symptoms in people with depression, with the impact being more pronounced in people with major depressive disorder. However, another study in BMC Research Notes(opens in new tab) found vitamin D made no significant difference compared to a placebo.
Another review(opens in new tab) pointed out that the relationship could work the opposite way. People with depression may be at increased risk of vitamin D deficiency because they are more likely to withdraw from social activity and spend less time outside.
There are other theories about the link between vitamin D and depression. One review, published in the Indian Journal of Psychological Medicine(opens in new tab), notes there are many vitamin D receptors in brain areas known to play a role in mood. These include the prefrontal and cingulate cortices. In addition, vitamin D regulates the hypothalamic-pituitary-adrenal axis, which influences mood.
The same review(opens in new tab) suggests another hypothesis that could be related to the immune system. Depression is correlated with higher levels of chronic inflammation, which happens when the immune response is triggered unnecessarily. Meanwhile, vitamin D is known to support immunity and have anti-inflammatory effects.
To complicate matters, the symptoms of vitamin D deficiency and depression have a degree of overlap.
According to the National Institute of Mental Health(opens in new tab), symptoms of depression include:
- Persistent sad or anxious mood
- Feelings of hopelessness
- Decreased energy and fatigue
- Aches or pains without a clear physical cause that do not ease with treatment
- Loss of interest or pleasure in hobbies and activities
- Thoughts of death or suicide