🧠 Why your vitamin D levels could change your mood

Could our daily mood be influenced by a simple nutrient that our body produces in sunlight? While depression affects millions of people worldwide, researchers are exploring unexpected avenues to understand the mechanisms that govern our mental well-being. This scientific quest now leads us to question the role of a very particular vitamin, present in our body but whose effects on our psyche remain mysterious.

A comprehensive analysis published in Biomolecules and Biomedicine reveals that adults with reduced vitamin D levels are more likely to suffer from depression, particularly when blood concentrations fall below a certain threshold. However, scientists clarify that this correlation does not necessarily mean that vitamin D deficiency directly causes depression. This important distinction opens the door to questions about the nature of the relationship between our nutritional status and our mental health.


From a biological perspective, the link between vitamin D and mood appears coherent. This vitamin acts in brain areas involved in emotion regulation, where its receptors are particularly numerous. Its active form contributes to proper functioning of communication between neurons, reduces nerve inflammation and helps maintain mineral balance in cells. These biological mechanisms are precisely those found to be disrupted in depressed individuals.

The research team examined sixty-six observational studies from thirty-one different countries, selected from over eight thousand scientific publications. Faced with the diversity of vitamin D measurement methods and depression assessment tools used in these studies, the researchers opted for a narrative synthesis rather than a classic meta-analysis. This approach allowed them to account for the methodological specificities of each study while identifying general trends.

The results show that in nearly fifty cross-sectional studies, low vitamin D levels consistently correspond to higher depression scores. The critical threshold appears to be around very low concentrations, where the association with depressive symptoms becomes particularly marked. Some analyses suggest these links could be more pronounced in women, indicating potentially different effects depending on sex.

Prospective studies, which follow participants over time, present a more nuanced picture. Some research conducted with elderly or community populations indicates that people deficient in vitamin D at the start of the study more frequently develop depressive symptoms later. However, other large studies, including biobank data, did not detect a significant link between vitamin D status and the onset of major depression.

The researchers emphasize the need for more rigorous studies, with repeated vitamin D measurements and objective data on sun exposure. Vlad Dionisie, professor at Carol Davila University of Medicine and Pharmacy, recommends a pragmatic approach: checking vitamin D status in depressed patients and correcting proven deficiencies, while continuing research to determine whether supplementation can truly prevent depression.

How vitamin D functions in the body

Vitamin D is unique among vitamins because our body can synthesize it naturally when our skin is exposed to sunlight. This skin production represents the main source of vitamin D for most people, although some foods like fatty fish, eggs and fortified dairy products can also provide it. Once produced or absorbed, vitamin D undergoes two successive transformations in the liver then kidneys to become active.

This active form of vitamin D acts like a hormone in our body, binding to specific receptors present in many tissues. Its most well-known role concerns bone health, as it promotes calcium and phosphorus absorption at the intestinal level. Without sufficient vitamin D, our body cannot properly use dietary calcium, which can weaken bone structure and increase fracture risk.

Beyond its action on the skeleton, vitamin D influences many other physiological systems. It modulates immune system functioning, participates in blood pressure regulation and intervenes in cell growth. These multiple effects explain why a deficiency can manifest through varied symptoms, ranging from persistent fatigue to increased susceptibility to infections.

Vitamin D concentration in an individual (vitamin D status) varies considerably according to season, geographic latitude, age and lifestyle habits. Elderly people, people with dark skin, those who get little sun exposure or who systematically use sunscreen have an increased risk of deficiency. Blood measurement of 25-hydroxyvitamin D remains the best indicator for assessing an individual's vitamin status.