Can vitamin D, omega-3 fats, or other nutrients ward off depression, as many labels imply? "Support" claims are rarely backed by good evidence. “All kinds of supplements claim to boost your mood or prevent depression,” says Marjolein Visser, professor of nutrition and health at Vrije Universiteit in Amsterdam. Her MooDFOOD trial tested a supplement with five nutrients: omega-3s (1,060 milligrams of EPA +   350 mg of DHA), selenium (30 micrograms), folic acid (400 mcg), and vitamin D (20 mcg) plus calcium (100 mg). Visser and her team randomly assigned 1,025 overweight or obese adults to take either the supplement or a placebo every day. All had depressive symptoms but had not been diagnosed with full clinical depression.