A growing body of research points to the importance of omega-3 fatty acids, and those found in fish oil in particular, for neurobehavioral health. While the effects may be modest in some studies, they emerge in a range of mental health conditions and implicate specific environmental contributions in these disorders.
The benefits of fish oil supplementation have been demonstrated in Attention-Deficit/Hyperactivity Disorder (e.g., 1), depression (e.g., 2) and schizophrenia (e.g., 3), in which the eicosapentaenoic acid (EPA) component of fish oil appeared to provide the lion’s share of benefits. This may be due to the anti-inflammatory influence of EPA in the body, as inflammation plays an increasingly-appreciated role in the emergence of a range of mental and physical states of disease.
Fish oil is also rich in docasahexanoic acid (DHA), the most abundant fatty acid in the human brain. Our bodies can synthesize DHA from other food sources, and it is found in breast milk and appears to be very important in healthy brain development in infants. Low levels of DHA have been implicated in neurodegenerative disorders, and supplementation has been found to protect the brain from the neurotoxic effects of neurodegenerative disease and brain injury, even in adulthood. One fascinating 2011 study found that supplementation of large amounts of DHA and EPA (but particularly DHA) following induced traumatic brain injury (TBI) in rats prevented the cascade of metabolic disturbance associated with the damage to these neurons following TBI (measured by subsequent beta-amyloid precursor protein levels, which are high in chronic traumatic encephalopathy and Alzheimer’s Disease).
Note, however, that fish do not endogenously produce EPA and DHA, but rather obtain it from algae and seaweed that they eat. Eating foods rich in these ocean sources of EPA & DHA should also provide the benefits observed from fish oil supplementation, but without the associated contaminants and mineral deposits as found in fish (particularly larger fish like tuna), which can be harmful in large quantities.