Vitamin D caused a lot of talk at the start of the pandemic. COVID-19. This vitamin contributes to the proper functioning of the innate immune system and infected people generally displayed lower vitamin D levels than the rest of the population. It also plays a major role in calcium and phosphorus absorption, bone mineralization and muscle function. A new study today suggests that vitamin D supplementation may relieve symptoms in people with depression.
Vitamin D is synthesized directly, in the skin, via exposure to solar UVB rays, from cholesterol derivatives naturally present in the body. But this source is very variable according to the regions of the world, which are more or less sunny. Fortunately, food supplements this intake: fatty fish, eggs, meat, mushrooms and fortified dairy products are good sources of vitamin D. For adults, an intake of 15 micrograms per day is recommended. In fact, many people have a vitamin D deficiency, especially in our latitudes and especially in the elderly — the ability to absorb and synthesize vitamin D decreases with age.
In recent years, several studies have suggested 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 heavy impact on the daily life of people affected and constitute a significant burden of disease. Antidepressant drugs can be effective, but are sometimes insufficient. As a result, other avenues of treatment are being sought, particularly on the nutrition side.
More than 40 studies reviewed
Studies have shown that biologically active vitamin D, the nuclear vitamin D receptor, and vitamin D activating and metabolizing enzymes 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, disturbances of which have been 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 — the majority of them have provided no evidence of any positive effect. Researchers from the University of Eastern Finland have once again looked into the matter. They engaged in a new meta-analysis of past studies, sifting through the results of 41 studies conducted 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 a placebo in relieving depressive symptoms in people with depression. There were major differences in the doses of vitamin D used, but the vitamin D supplement was generally 50 to 100 micrograms per day. ” Despite high heterogeneity, vitamin D supplementation ≥ 2,000 IU/day appears to reduce depressive symptoms “, concluded the team. However, the results are to be qualified.
Potential efficacy in major depressive disorder
The 41 studies reviewed involved more than 53,000 individuals, most (84%) being women, with or without depression; participants were supplemented with vitamin D or were on placebo. Sample sizes varied greatly (from n=42 to n=36282). Similarly, the duration of the interventions varied between five days and five years, and the single doses of vitamin D varied from 400 to 500,000 IU (and, calculated per day of intervention, from 400 IU to approximately 14,000 IU).
Analyzes suggest that vitamin D supplementation appears to reduce depressive symptoms, particularly in people diagnosed with major depressive disorder and in women with perinatal depression, the team said. Also, the effect of supplementation appears to be greater when supplements are taken for a short duration (less than 12 weeks). In terms of dosage, supplements below 4,000 IU/day had a weak to moderate effect; beyond that, the effect was greater. Additionally, supplementation had only 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 suggest that vitamin D supplementation has beneficial effects in people with major depressive disorder, as well as those with milder, clinically significant depressive symptoms. », summarizes the team. Even if their meta-analysis includes a very large number of individuals, the researchers remain cautious about the results obtained: they emphasize that the evidence for an association between vitamin D and depression remains fragile due to the heterogeneity of the populations studied and the risk of bias associated with a large number of studies.
This meta-analysis nevertheless confirms the potential therapeutic usefulness of vitamin D in psychiatry, particularly in cases of major depressive disorder and perinatal depression. ” These findings will encourage further high-level clinical trials in patients with depression to better understand the possible role of vitamin D supplementation in the treatment of depression. », conclusion Tuomas Mikolaa researcher at the Institute of Clinical Medicine at the University of Eastern Finland and lead author of the meta-analysis.