The deficiency of nutrients in diets causes biochemical imbalances that can affect the brain. Nutritional deficiency in omega-3 fatty acids are linked to psychiatric disease, but the biological basis was unknown until now. A study, published in Nature Neuroscience, demonstrates that mice fed a life-long diet deficient in omega-3s lose brain functions that require the cannabinoid receptor and these mice exhibit depressive behavior.
Omega-3s and the brain
Omega-3s are essential fatty acids that our bodies cannot make from scratch. The body gets omega-3s by either metabolizing alpha-linoleic acid or by direct intake of omega-3s from foods or supplements. Omega-3s, especially DHA (docosahexaenoic acid) is necessary for normal nerve function in the brain, according to research by the American Psychological Association. Studies showed that people with schizophrenia, bipolar disorder, obsessive-compulsive disorders, and attention deficit disorder have low omega-3 levels.
Omega-3s and cannabinoid receptors
To study the effect of omega-3s on brain function, researchers established two groups of mice; one was fed a life-long diet deficient in omega-3s and the other group was fed a normal diet. The researchers found that the mice deficient in omega-3s suffered a complete loss of function of their brain cannabinoid receptors, but not of other receptors. Cannabinoid receptors are widely distributed in the brain and link food lipids to brain activity and behavior. These receptors are activated by intra-brain substances, called endocannabinoids. The researchers found that the mice with the omega-3-deficient diet had greater anxiety, spent long times without moving, and had fewer social interactions with other mice, indicating that the mice were depressed. The authors write: “Finally, the dietary-induced reduction of CB1R (cannabinoid CB1 receptor) functions in mood-controlling structures was associated with impaired emotional behavior” (Lafourcade, M. et al.). When the omega-3-deficient mice were given an anti-depressant, some of the behaviors were reversed.
This study demonstrates that brain functions can be disrupted by a dietary deficiency, resulting in emotional disturbances and changes in behaviors. Western diets have become more and more deficient in omega-3 fatty acids, threatening our mental health. The ratio of omega-6 to omega-3 fatty acids has been increasing in Western diets. Although omega-6 fatty acids are required for optimal health, an overabundance of omega-6s has adverse effects. The new studies suggest that chronic deficiency of omega-3s in the diet of pregnant women may predispose the children to mood disorders later in life. Further studies are needed to determine whether treatment with omega-3s can reverse depression and other mood disorders.
Lafourcade, M. et al. Nutritional omega-3 deficiency abolishes endocannabinoid-mediated neuronal functions. Nature Neuroscience (2011) 14: 345
Mashour, G.A. The Food for Mood. Science Translational Medicine (2011) 3: 74ec35