Some studies have suggested that lower levels of certain nutrients, such as omega-3 polyunsaturated fatty acids, folic acid, vitamin D, or selenium, are linked to higher levels of depressive symptoms. According to two studies that tested combinations of ingredients with purported antidepressive effects, dietary supplements don’t help prevent major depressive disorder (MDD) in people at high risk for it or reduce symptoms in those who have it.
In a 2019 study in the Journal of the American Medical Association, 1,025 overweight or obese people with depressive symptoms but no recent MDD episode were given supplements containing omega-3 fats, selenium, folic acid, and vitamin D or a placebo; half also took part in food-related behavioral counseling. After a year, neither the supplements nor the therapy, alone or in combination, reduced the likelihood of MDD episodes compared to the placebo.
And in a 2019 Australian study in the Journal of Affective Disorders, 158 people with MDD took a nutraceutical formula (omega-3s, SAM-e, 5-HTP, zinc, and folic acid) or a placebo, in addition to their customary medication. After eight weeks, the supplement group was less likely to have an improvement in depressive symptoms or to experience remission than the placebo group.