October 19, 2012 — Icelanders believe that their high consumption of ocean fish and fish oil helps them cope. Oil-rich cold-water fish like salmon, cod, and sardines, fish oil supplements, and some plant-based foods like walnuts contain omega-3 polyunsaturated fatty acids, which research on other mood disorders suggests have an antidepressant effect. We've known for quite a while that eating fish correlates negatively with major depressive disorder.
Omega-3s affect the nervous system in other ways as well, which we're still coming to understand. We do know that nerves in the brain are so sensitive to omega-3 levels that a deficiency leads to problems with learning and memory, and evidence shows supplementation may protect against nerve damage due to trauma or aging. Omega-3s can change the composition of the membranes that surround cells in the brain and blood, and may improve their ability to function.
It's not just the absolute amount of omega-3s that you take in, but also the amount relative to your levels of omega-6 fatty acids. The risk for depression may increase with a high ratio of omega-6 fatty acids — found in corn, safflower, and soybean oil, and common in processed foods — to omega-3s.
Read the full story in the Atlantic Monthly