Vitamin D
Studies show [23] that people with depression tend to have lower levels of vitamin D in their bodies than people without it. There is also a correlation between the severity of depression and the severity of a depressed person’s vitamin D deficiency.
Researchers believe [24] that vitamin D consumption may help treat depression in several ways, such as by regulating mood and reducing inflammation. A recent review of studies [25] found that vitamin D supplements improved the condition of people with major depression.
Another study [26] found that injecting vitamin D deficient people with a single 300,000 IU dose of vitamin D improved their depressive symptoms.