Omega-3 fatty acids, which are not manufactured by the body and must be obtained from the diet, are essential to brain development and function. Modern Western diets contain a lower amount of these fats than the diets of earlier generations, while containing a higher level of omega-6 fatty acids such as linoleic acid. Growing research tentatively links this dietary alteration to increases in depression, learning disabilities, and attention deficit disorder (see related article, Crime Times, 1999, Vol. 5, No. 1, Page 1), and now clinical and epidemiological studies also hint at a link to increases in aggressive or violent behavior.
Joseph Hibbeln et al. have conducted a series of studies examining the effects of omega-3 and omega-6 fatty acid levels on aggression, hostility, and rates of homicide. In one study, the researchers analyzed economic measures of omega-6 consumption across time and countries to see if these were related to trends in homicide rates. They report finding evidence of "a striking correlation between greater apparent consumption of linoleic acid from seed oils and greater risk of homicide mortality across time, from 1961 to 2000, among five Western countries [the United States, the United Kingdom, Australia, Canada, and Argentina]." Hibbeln et al. say that this finding, and earlier research by the same authors showing that greater intakes of omega-3 rich seafood correlate with lower rates of homicide mortality across 36 countries, "are consistent with animal studies and controlled intervention trials in humans [Gesch et al., Crime Times, Volume 8, Number 3, 2002, page 1] that reported decreased measures of aggression or violence by increasing intakes of long chain omega-3 fatty acids relative to omega-6 intake."
Hibbeln et al. say, "One mechanism that may link excessive linoleic acid intake or deficient EPA and DHA status is a deficit in serotonergic neurotransmission in the frontal cortex, which has been repeatedly implicated in the pathophysiology of lifelong impulsive and violent behaviors." They cite animal research showing that dietary deficiencies of omega-3 fatty acids during fetal development and early postnatal life are linked to residual deficits in serotonergic neurotransmission.
The researchers conclude that while multiple factors contribute to aggression and violence across cultures, and the possible associations between omega-3 and omega-6 fatty acids and homicide rates need to be further investigated, "dietary interventions that reduce linoleate intake and improve the tissue status of omega-3 fatty acids and other basic nutrients can potentially become relatively cost-effective measures for reducing the pandemic of violence in Western societies, just as dietary interventions are reducing cardiovascular mortality."
In a separate study, Hibbeln and colleagues note that elevated levels of corticotrophin-releasing hormone (CRH) in the cortical- hippocampal-amygdala pathway increase fear and anxiety, emotions that play a strong role in violent behavior. Levels of two prostaglandins that increase CRH activity in this pathway are reduced by omega-3 fatty acids. Thus, the researchers theorize, a diet low in omega-3 fatty acids could lead, indirectly, to increased expression of CRH and thus to elevated levels of violence- provoking fear and anxiety.
To test this theory, the researchers measured plasma levels of fatty acids in 21 perpetrators of domestic violence. They found that lower levels of DHA predicted greater cerebrospinal fluid levels of CRH.
"Randomized, placebo-controlled trials are needed to determine if supplementation with DHA and EPA can decrease elevated levels of CRH and improve behavioral outcomes among subjects with aggressive and violent behaviors," they say. Hibbeln and colleagues note that additional findings support the link between low omega-3 fatty acids and behavioral disorders. These findings include:
"Increasing homicide rates and linoleic acid consumption among five Western countries, 1961-2000," Joseph R. Hibbeln, Levi R. C. Nieminen, and William E. M. Lands, Lipids, Vol. 39, No. 12, 2004, 1207-13. Address: Joseph R. Hibbeln, Section on Nutritional Neurochemistry, LMBB, NIAAA, 31 Center Drive, Building 31/1B 58, Bethesda, MD 20892, firstname.lastname@example.org.
"Omega-3 status and cerebrospinal fluid corticotrophin releasing hormone in perpetrators of domestic violence," Joseph R. Hibbeln, Garth Bissette, John C. Umhau, and David T. George, Biological Psychiatry, Vol. 56, 2004, 895-97. (See address above.)