Nutrition has been implicated as one of the causes and risk factors for depression, and accordingly, one approach to depression involves the use of nutritional supplements or changes in diet. A study of older adults found that poor nutrition was a strong predictor of depressive symptoms a year later. A few nutrients have been studied directly for their antidepressant properties, both to treat and prevent depression, as well as related conditions such as anxiety.
Omega 3 fatty acids have been proposed as a treatment for depression, often suggested to be combined with other treatments. One small pilot study of childhood depression (ages 6–12) suggested that omega 3 may have therapeutic benefits for treating childhood depression. A 2005 review of the scientific literature concluded that there were several different independent lines of evidence suggesting that omega-3 fatty acids play a role in depression, and that the theory of omega-3's role in depression was biologically plausible. The evidence includes a few double-blind randomized control trials, epidemiological studies linking low fish consumption (the primary source of omega-3) to increased rates of depression, and case-control and cohort studies of unipolar and postpartum depression indicating low blood levels of omega-3 in depressed patients.
Other essential nutrients
Folic acid and Vitamin B12 have also been proposed as a treatment for depression, especially when used in conjunction with other treatments. In particular, folic acid has been shown to improve the treatment response to other antidepressants.