When researchers from Ohio State University evaluated blood samples taken from 43 older adults (average age 67), they found that study participants with high ratios of omega-6 to omega-3 not only had higher levels of various compounds involved in inflammation, but were more likely to suffer from depression.
Both depression and stress promote the production of pro-inflammatory cytokines. Researchers measured a number of these pro-inflammatory compounds including tumour necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and the IL-6 soluble receptor (sIL-6r). Symptoms of depression were assessed using the Center for Epidemiological Studies Depression Scale.
Levels of pro-inflammatory cytokines increased progressively as depressive symptoms increased. But when depressive symptoms were combined with high omega-6:omega-3 ratios, levels of proinflammatory cytokines skyrocketed by up to 40% more than normal—far beyond the 18% increase resulting from the presence depressive symptoms alone.
Chronic inflammation has already been linked to heart disease, type 2 diabetes, osteoporosis, cognitive decline and Alzheimer's. Earlier epidemiological (population) studies have also linked higher levels of pro-inflammatory cytokines with depressive symptoms. This new study suggests that a diet that is rich in omega-6 fats but includes few of the foods rich in omega-3 fats—such as the standard American diet—promotes not only inflammation, but depression.
The positive take-away is that increasing consumption of foods rich in omega-3s, while decreasing consumption of omega-6-rich foods, can provide some protection against depression, particularly as depressive symptoms increase.
Omega-3s are found in cold water fish, nuts, such as walnuts, and flaxseeds. Alpha-linolenic acid (ALA), the omega-3 in nuts and seeds, can be converted—albeit inefficiently—in the body to the omega-3s found in fish, eicosapentaenoic acid (EPA) and docosahexaenioc acid (DHA).
EPA improves blood flow and is also suggested to affect hormones and the immune system, both of which have a direct effect on brain function. DHA is active in the membrane of ion channels in the brain, making it easier for them to change shape and transmit electrical signals, and is involved in serotonin metabolism (reduced serotonin production and/or activity is a key factor in depression). Practical Tip: Be of good cheer. Cut back on sources of omega-6 fats, such as beef, and corn, palm, peanut, safflower and sunflower oils. Enjoy a handful of omega-3-rich walnuts and/or flaxseeds daily, and a serving of cold water fish, such as scallops, at least 3 times each week.