Omega-3s are a unique type of polyunsaturated fatty acid that are abundant in fish and shellfish. The two
main seafood omega-3s are EPA* and DHA*. These omega-3s benefit heart health, the immune system and
brain function, and are essential for infant brain growth and development. DHA is highly concentrated in the brain and retina where it participates in vision, communication between cells, nerve impulse transmission, and the protection of brain cells. Details of how these fatty acids affect mental function are beginning to emerge. In several mental disorders, these omega-3s are significantly below those observed in healthy people.
Serious mental disorders affect about one in 17 American adults and are the leading cause of disability in the U.S., according to the National Institute of Mental Health. Major depressive disorder—a prolonged period of feeling low or hopeless—affects about 14 million Americans at any given time. The condition interferes with a person’s ability to work, sleep, eat and experience pleasure and can be disabling.
Depression is most common in countries with the lowest consumption of seafood, such as the U.S. and Germany. It occurs least often in countries such as Japan, Korea and Iceland, where seafood consumption is high. But this observation does not mean that low seafood consumption causes depression. However, we are learning that the omega-3s in fish may be helpful in treating patients with depression. Several studies in patients being treated medically for depression reported marked improvement in patients’ symptoms when small amounts of EPA were added to the treatment. Doses of 1 to 2 grams of EPA/day were more effective than larger amounts and were without harmful side effects. Results also suggest that EPA is more effective than DHA. How EPA might bring about these improvements is not known. While these results are encouraging, much more information from larger rigorous studies is needed before we can consider these findings conclusive.