Meta-analysis suggests vitamin D may be effective for depression

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Vitamin D was a hot topic at the start of the COVID-19 pandemic. This vitamin contributes to the proper functioning of the innate immune system, and infected individuals typically had lower levels of vitamin D than the rest of the population. It also plays an important role in calcium and phosphorus absorption, bone mineralization, and muscle function. A new study today suggests that vitamin D supplements may improve symptoms in people with depression.

Vitamin D is synthesized directly in the skin by exposure to UVB sunlight from cholesterol derivatives naturally present in the body. But this source is very variable depending on the regions of the world that are more or less sunny. Fortunately, dietary supplements supplement this intake: fatty fish, eggs, meats, mushrooms, and fortified dairy products are good sources of vitamin D. The recommended intake for adults is 15 micrograms per day. In fact, many people are deficient in vitamin D, especially in our latitudes and especially in older people – the ability to absorb and synthesize vitamin D decreases with age.

In recent years, several studies have shown that there may be a link between vitamin D deficiency and depression, a common mental disorder that affects 5% of adults worldwide, according to the World Health Organization. Symptoms of depression (gloomy mood, loss of pleasure or interest in activities, difficulty concentrating, loss of self-esteem, sleep disturbances, negative thoughts, etc.) have a severe impact on the daily life of affected people and constitute a significant burden of the disease. Antidepressants can be effective, but sometimes they are not enough. As a result, other avenues of treatment are being sought, especially in the field of nutrition.

Over 40 studies reviewed

Studies have shown that biologically active vitamin D, the nuclear vitamin D receptor, and enzymes that activate and metabolize vitamin D are present in brain neurons, glial cells, and macrophages. Therefore, it has been suggested that it may play a role in the regulation of central nervous system functions that are associated with depression. This hypothesis has been supported by several cross-sectional studies that have shown an association between depressive symptoms and vitamin D deficiency.

However, meta-analyses conducted so far on the effects of vitamin D supplementation on mental health have been inconclusive—most have not provided any evidence of any beneficial effect. Researchers from the University of Eastern Finland have revisited this issue. They conducted a new meta-analysis of past studies by analyzing the results of 41 studies from around the world. All were randomized, placebo-controlled trials in different adult populations.

The results of this new meta-analysis show that vitamin D supplementation is more effective than placebo in relieving symptoms of depression in people with depression. There was great variation in the doses of vitamin D used, but vitamin D supplementation was typically 50 to 100 micrograms per day. “Despite high heterogeneity, vitamin D supplementation ≥2000 IU/day appears to reduce depressive symptoms,” the team concluded. However, the results must be qualified.

Potential efficacy in major depressive disorder

The 41 studies reviewed included more than 53,000 people, the majority (84%) were women with or without depression; participants received vitamin D or a placebo. Sample sizes varied greatly (from n=42 to n=36282). Similarly, the duration of interventions ranged from five days to five years, and single doses of vitamin D ranged from 400 to 500,000 IU (and on an intervention day from 400 IU to about 14,000 IU).

Analyzes show that vitamin D supplements appear to reduce symptoms of depression, especially in people diagnosed with major depressive disorder and in women with perinatal depression. Also, the effect of supplements appears to be greater when supplements are taken for a short period of time (less than 12 weeks). In terms of dosage, supplementation below 4000 IU/day had a weak to moderate effect; moreover, the effect was greater. In addition, supplementation had a small to moderate effect when people had low (≤ 50 nmol/L) to sufficient (> 50 nmol/L) serum vitamin D levels at the start of the experiment.

“Our results show that vitamin D supplementation has a beneficial effect on people with major depressive disorder, as well as people with milder, clinically significant depressive symptoms,” the team concludes. Even if their meta-analysis includes a very large number of people, the researchers are still cautious about their results: they emphasize that the evidence for an association between vitamin D and depression remains fragile due to the heterogeneity of the studied populations and the risk of bias associated with a large number of studies.

Nevertheless, this meta-analysis confirms the potential therapeutic utility of vitamin D in psychiatry, especially in cases of major depressive disorder and perinatal depression. “These results will stimulate new high-level clinical trials in patients with depression to better understand the possible role of vitamin D supplementation in the treatment of depression,” concludes Tuomas Mikola, research fellow at the Institute of Clinical Medicine at the University of Eastern Finland. and lead author of the meta-analysis.

T. Mykola et al., Critical Reviews in Food Science and Nutrition.

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