We seem pretty clear on the idea that diet can prevent certain diseases, like heart disease and diabetes. Diet can also effect the brain. It can influence mood and cognition. A diet that is high in refined carbohydrates, for example, can create insulin insensitivity. Insulin insensitivity can make a person prone to mood swings or depression.
There have been a number of studies that have looked at the relationship between diet and mental health. A study appearing in the Archives of General Psychiatry (2009; 66(10): 1090-8) found that diet can affect the incidence of depression. The study followed the dietary habits of 10,094 subjects for 4.4 years. During the course of the study, 480 were diagnosed with depression. According to the study, the subjects adhering to the Mediterranean diet had a lower incidence of depression. The Mediterranean diet consists of high consumption of fruits, vegetables and nuts. It also recommends a high amount of monounsaturated oil (olive oil), and low saturated fat consumption, along with low amounts of high-fat meat and dairy, and high amounts of fish and legumes.
Various vitamin deficiencies can lead to depression. A number of studies show the value of omega-3 fatty acids for patients with depression. One such study was published in the British Journal of Psychiatry (2006; 188: 46-50 ). It was a 12-week, randomized, double-blind, placebo-controlled study involving 75 individuals with bipolar depression, adjunctive treatment with ethyl-eicosapentaenoic acid (EPA) was found to be well-tolerated and effective in reducing symptoms of depression. In Acta Psychiatry Scandinavia (2006; 113(1): 31-5 ) , a study demonstrated that omega-3 supplementation helped with post-partum depression. Another study, published in the American Journal of Psychiatry (2006; 163(6): 1098-100 ), found that omega-3 supplementation was beneficial to children suffering with depression.