A deficiency of omega-3 fatty acids in Western diets has been implicated in many disorders. A new laboratory study of a diet low in omega-3 fatty acids has shown that reduced levels of omega-3 had deleterious consequences on brain synaptic functions and emotional behavior. Specifically the study revealed that without adequate omega-3s, the receptors in the brain that react with cannabinoids suffer a complete loss of function. Cannabinoid receptors in the brain interact with the body’s naturally produced cannabinoids, and also with plant-derived cannabis compounds (from marijuana).

In industrialized nations, diets have been impoverished in omega-3 essential fatty acids since the beginning of the 20th century. The dietary ratio of omega-6 polyunsaturated fatty acids to omega-3 polyunsaturated fatty acids has increased continuously over the course of the 20th century. These fatty acids are “essential” lipids because the body cannot synthesize them. They must therefore be provided through food and their dietary balance is essential to maintain optimal brain functions.

Olivier Manzoni (Head of Research Inserm Unit 862, “Neurocentre Magendie”, in Bordeaux and Unit 901 “Institut de Neurobiologie de la Méditerranée” in Marseille), and Sophie Layé (Head of Research at INRA Unit 1286, “Nutrition et Neurobiologie Intégrative” in Bordeaux) and their co-workers hypothesized that chronic malnutrition during intra-uterine development, may later influence synaptic activity involved in emotional behavior (e.g. depression, anxiety) in adulthood.

To verify their hypotheses, the researchers studied mice fed a life-long diet imbalanced in omega-3 and omega-6 fatty acids. They found that omega-3 deficiency disturbed neuronal communication specifically. The researchers observed that only the cannabinoid receptors, which play a strategic role in neurotransmission, suffer a complete loss of function. This neuronal dysfunction was accompanied by depressive behaviors among the malnourished mice.

Among omega-3 deficient mice, the usual effects produced by cannabinoid receptor activation, on both the synaptic and behavioral levels, no longer appear. Thus, the CB1R receptors lose their synaptic activity and the antioxidant effect of the cannabinoids disappears.

Consequently, the researchers discovered that among mice subjected to an omega-3 deficient dietary regimen, synaptic plasticity, which is dependent on the CB1R cannabinoid receptors, is disturbed in at least two structures involved with reward, motivation and emotional regulation: the prefrontal cortex and the nucleus accumbens. These parts of the brain contain a large number of CB1R cannabinoid receptors and have important functional connections with each other.

“Our results can now corroborate clinical and epidemiological studies which have revealed associations between an omega-3/omega-6 imbalance and mood disorders”, explain Olivier Manzoni and Sophie Layé. “To determine if the omega-3 deficiency is responsible for these neuropsychiatric disorders additional studies are, of course, required”.

In conclusion, the authors estimate that their results provide the first biological components of an explanation for the observed correlation between omega-3 poor diets, which are very widespread in the industrialized world, and mood disorders such as depression (Courtesy of Eurekalert).

The abstract and PDF of this study are available free online here:

Omega-3 fatty acid deficiency, cannabinoid receptors, and depression

Reference: Mathieu Lafourcade, et al. Nutritional Omega-3 deficiency abolishes endocannabinoid mediated neuronal functions. Nature Neuroscience, Published (web) January 30, 2011. doi:10.1038/nn.2736