Green veggies: spinach, broccoli, Brussels sprouts

These green veggies are a source of folate, a B vitamin that's essential for the body's production of serotonin.

In one meta-analysis, researchers found that individuals with depression consume less folate and have lower blood levels of the vitamin compared to those without depression.

In addition to increasing the risk for depression, poor intake of folate is also linked to fatigue and poor memory.

Somer recommends consuming at least 400 micrograms of folate per day, an amount found in 1 ½ cups of sautéed spinach. Beans, peas, lentils, avocado and strawberries are other good sources of folate.