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Vitamin D supplements reduce depressive symptoms in adults - new meta-analysis

by University of Eastern Finland

Vitamin D - Credit Unsplash CC0 / Public Domain

An extensive meta-analysis suggests that vitamin D supplementation may alleviate depressive symptoms in adults with depression. Conducted by an international team of researchers, the meta-analysis includes dozens of studies from around the world.


Low Vitamin D levels have been consistently 'linked with' impaired immunity, poor heart health, and weak bones and teeth - and also with many different mental conditions, including ADHD, autism, dementia, and depression.  However, association studies alone do not provide definitive evidence for cause-and-effect. 

This new evidence that Vitamin D supplementation can reduce depressive symptoms is therefore important, because it comes from a systematic review of randomised, double-blind, placebo-controlled trials, which can demonstrate causality.

The authors have provided a comprehensive and detailed review (which is open-access) - highlighting the many difficulties in conducting clinical trials of Vitamin D supplementation in general, and for 'depression' in particular. As ever, further research is still needed.

Meanwhile, however, Vitamin D insufficiency - if not severe deficiency - now affects most of the UK population in autumn and winter, if not all year round, particularly people with darker skins and/or indoor lifetyles. Bright sunlight is the main natural source, as very few foods provide Vitamin D (fish and liver are the richest dietary sources). 

Supplementation is therefore recommended for most people - but only at 10 mcg/day (400 IU) in the UK - far lower than the doses shown to be effective against depression in this review, which were 50 mcg/day (2000 IU) or more.  (The Upper safe level is 100mcg, or 4000 IU) 

And it's also worth flagging that one very serious limitation of almost all trials of Vitamin D to date - for any indication - is their failure to consider magnesium status, as: 

This is important - as most people's diets fail to provided recommended dietary intakes of magnesium. And deficiencies of this nutrient have repeatedly been linked with depression, anxiety and related conditions.

For more details of this new research, see:

See also:

And for more information on Vitamin D, please see the following lists, which are regularly updated:

Depressive symptoms cause a significant disease burden worldwide. The therapeutic efficacy of current antidepressants is often insufficient, which is why further ways to alleviate the symptoms of depression have been sought, for example, from nutritional research.

Vitamin D is believed to regulate central nervous system functions the disturbances of which have been associated with depression.

In addition, cross-sectional studies have observed an association between depressive symptoms and vitamin D deficiency. However, previous meta-analyses on the effects of vitamin D supplementation on depression have been inconclusive. In a meta-analysis, results from several different studies are combined and analyzed statistically.

The new meta-analysis on the association of vitamin D supplementation with depression is the largest one published so far, including results from 41 studies from around the world.

These studies have investigated the efficacy of vitamin D in alleviating depressive symptoms in adults by randomized placebo-controlled trials in different populations. The studies included those carried out in patients with depression, in the general population, and in people with various physical conditions.

The results of the meta-analysis show that vitamin D supplementation is more effective than a placebo in alleviating depressive symptoms in people with depression. There were major differences in the vitamin D doses used, but typically the vitamin D supplement was 50–100 micrograms per day.

"Despite the broad scope of this meta-analysis, the certainty of evidence remains low due to the heterogeneity of the populations studied and the due to the risk of bias associated with a large number of studies," Doctoral Researcher and lead author Tuomas Mikola of the Institute of Clinical Medicine at the University of Eastern Finland says. The meta-analysis is part of Mikola's Ph.D. thesis.

"These findings will encourage new, high-level clinical trials in patients with depression in order to shed more light on the possible role of vitamin D supplementation in the treatment of depression," Mikola concludes.

The meta-analysis was published in Critical Reviews in Food Science and Nutrition and carried out in international collaboration between Finnish, Australian and U.S. researchers.