Can vitamin D supplements help improve depression?

A new study published in Critical Reviews of Food Science and Nutrition has investigated vitamin D's effectiveness in reducing symptoms of depression in comparison to a placebo. A decrease in symptoms of depression was noticed, with low certainty, when Vitamin D supplements were administered in a dose equal to or more than 2,000 individual units (IU)  per day. 

Effect of Vitamin D Supplements on Symptoms

The study included 41 randomized controlled trials consisting of 53,235 test subjects. A small to moderate effect on symptoms of depression due to vitamin D supplementation was discovered. People with baseline vitamin D levels less than 50 nanomoles per liter (nmol/L) displayed a greater effect as compared to those with higher levels. Additionally, while doses up to 2,000 IU had a small to moderate effect, daily doses greater than 4,000 IU had a more significant impact. Furthermore, a greater response was seen when supplementation was taken for less than 12 weeks rather than for greater durations. 

Impact on Depressive Conditions

Conclusively, a positive impact was seen in 1,116 people suffering from clinical depression and on 407 subjects with perinatal depression. Moreover, a statistically significant positive effect was determined in patients who consumed antidepressants in combination with vitamin D supplements. Although, it was discovered that placebos had a favorable outcome when it came to a subgroup of healthy individuals who were not diagnosed with clinical depression. Also, the supplements had no significant impact on Seasonal Defective Disorder or symptoms of depression in older subjects. The investigators also admitted that the results were not certain because there was a risk of bias in 36.6% of the cases.

Underlying Mechanisms

It is still unknown how exactly vitamin D affects mental health. There is evidence to suggest that it influences the immune system and its consequent inflammation. Some studies have suggested that increased inflammation may be linked to mental health disorders and reducing it may be therapeutic. However, more studies need to be conducted before it can be recommended clinically, especially concerning what dose and for whom is it most beneficial. 

Influence on Depression Treatment

Currently, there is not enough evidence to use vitamin D supplements as an alternative depression treatment. However, it can be given to people who are already receiving other forms of treatment for depression.