The Societal Dimension

On April 16 2006, the New York Times carried an article by history teacher, Stephen Mihm, with the title, ‘Does Eating Salmon Lower the Murder Rate?’ While it might, at first glance, appear a curious association, yet the article was triggered by two separate scientific papers by Hibbeln in which he concluded that there might actually be a link between low consumption of omega-3 fatty acids and the murder rate. This highlighted an interesting new avenue of exploration in current research – the possibility that the ratio of omega-3 to omega-6s in our diet may be contributing to some of the problems that bedevil modern society. 

I shall discuss this ratio in more practical detail in Chapter 9, but for now I would like to take a look at the scientific evidence behind the societal dimension. 

We have already seen how too much omega-6s in our diet leads to a build-up of chemicals that lead to inflammation within our tissues and organs. As early as 1997, the pioneering Dutch investigator, Kalmijn, reported a collaborative study of diet and its relationship to cognitive function in 939 elderly men. Focusing on the adverse impact of what is called “oxidative stress” and its purported relationship to arterial disease, she looked for components in our ordinary diet that might have a good or bad influence on this. Since polyunsaturated fatty acids, or PUFAs, are highly susceptible to oxidation, and this in turn might worsen the effects of LDL (the “bad” cholesterol), maybe this could increase the risk of heart attacks and strokes. They now focused on the linoleic acid, which is both the commonest omega-6 in the Western diet and constitutes 90% of the polyunsaturated fatty acid in LDL cholesterol. Thus, in one of the first studies to examine the differential impacts of omega-3s versus omega-6s, they looked at fish consumption per se, the levels of omega-3s and omega-6s in the diet, and the intakes of vegetable type antioxidants such as beta-carotene, vitamins C and E and the so-called “flavonoids”. 

In fact they found that while the intake of the vegetable type antioxidants had no impact on cognitive function one way or another, high intake of linoleic acid was linked to increased risk of cognitive impairment. Meanwhile increased fish consumption reduced the risk. It looked as if there was a kind of tug of war going on, with excess of omega-6s pushing in an unhealthy direction and the omega-3s pushing in a beneficial direction. At the same time they were well aware that the omega-6, linoleic acid, was in itself essential to health. This was an important step in establishing the importance of healthy balance between omega-6s and omega-3 – or to put it simply, there had to be a healthy ratio of mega-6s to omega-3s.

Other researchers were approaching the same problem from a very different direction. 

Where most of the previous studies had focused on omega-3s in preventing or treating disease, in 2005 Fontani and colleagues at the University of Siena in Italy reported a study of the effects of DHA and EPA in healthy adults. In essence they wanted to know if increasing the intake of omega-3 fatty acids might improve the mental or physical status of a normal population. Their test population was a group of 33 volunteers, 13 males and 20 females, with a mean age 33 years, all judged to be physically and mentally fit through recruitment from local amateur athletic associations. These were compared to a control group of four males and 12 females of the same mean age.

The Italian researchers had already conducted an experiment in which they found that omega-3 supplementation appeared to influence mood in healthy subjects. Encouraged by this, they now compared the effects of fish oil containing high levels of omega-3, against olive oil as a control, while their test subjects performed a number of calibrated mental tasks. They began by completing a Profile of Mood States questionnaire, which measured their scales anger, anxiety, fatigue, confusion, depression – and a single positive mood, vigor. Next they performed a series of tests while reclining in front of a computer screen, meanwhile the investigators monitored brainwave patterns on an electroencephalogram (EEG), and peripheral nerve to muscle traces through electromyography (EMG). These tests included assessment of alertness, the ability to repress an unsuitable response, the ability to analyze and choose between different stimuli presented at the same time, and the ability to sustain attention.

Blood analysis showed that after omega-3 supplementation the omega-6 to omega-3 ratio was considerably reduced. The mood profile also improved, with less anger, anxiety and depression, accompanied by increased vigor. The tests also demonstrated an improved reaction time and better maintenance of attention in those given omega-3s when compared to the controls. In an objective confirmation of the subjective tests, the EEG and EMG traces showed changes that appeared to fit the mental changes.

As early as 1987, Virkkunen had suggested there might be some relationship between essential fatty acids and alcoholic, or habitually violent or otherwise impulsive offenders. In 2003, Zanarini and Frankenburg, at Harvard, reported a reduction of aggressive tendencies in women with borderline personality disorder who were given 1g of EPA a day. In 2004 Hibbeln and his colleagues (Iribarren) arrived at similar conclusions from a new investigation of the on-going cross-sectional study of young adults, known as “The CARDIA Study”, which had been monitoring the progress of 5115 healthy black and white men and women since the mid 1980s. Based in Birmingham, AL, Chicago, IL, Minneapolis, MN, and Oakland, CA, all of these test subjects had been aged 18-30 at the start of the investigation. But now, when Hibbeln and colleagues looked at levels of DHA and fish rich in omega-3 fatty acids in their diets, they found that DHA consumption was associated with a reduction in levels of hostility. 

A number of similar clinical intervention studies in both animals and humans have shown that supplementing diet with omega-3s reduces hostility, aggression and violent behavior, as well as recurrent self-harm. At least part of this pattern appears to be reversible, with improvements in mood and behavior through treatment with omega-3s. But several authorities have also questioned the possibility that part of the problem might reflect more permanent changes in brain development through omega-3 deficiency in pregnancy, with the prevailing imbalance of omega-6s to omega-3s lowering serotonin levels at critical periods of fetal and infant brain development, notably when the developmental links between the emotional and impulsive centers of the primitive limbic system are laying down important connections with the higher control centers in the frontal lobes.

This then was the background to the article in The New York Times, which drew upon Hibbeln’s conjecture that there might even be a link between omega-6 to omega-3 imbalance and that most violent form of aggression – murder.

In his second paper on this subject, published in 2004 with the provocative title, ‘Increasing homicide rates and linoleic acid consumption among five Western countries,’ he and his colleagues examined the possibility that an increasing preponderance of omega-6s may have contributed to violent behavior at whole societal level. The five countries in the spotlight were Argentina, Australia, Canada, the United Kingdom and the United States. Homicide mortality rates were obtained from the judicial authorities of each country and linoleic acid intake calculated from seed oil intake, with the assistance of data from the World Health Organisation. 

They concluded that greater consumption of linoleic acid did appear to correlate with higher rates of homicide mortality. I should caution that such a correlation on its own does not amount to proof, but it certainly raises some interesting questions for politicians, sociologists, nutritionists and the judicial authorities. Are Hibbeln and his colleagues being unreasonable when they suggest that randomized controlled trials are now needed to determine if reducing the high intake of linoleic acid through alternative compositions of seed oils can reduce the risk of violent behaviors in our society?

 Further Reading: 

Buydens-Branchey L, Branchey M, et al (2005).  N-3 polyunsaturated fatty acids decrease feelings of anger in a population of substance abusers. Neuropsychopharmacology 30(1):S87-S88.

Buydens-Branchey L, Branchey M, et al (2003). Polyunsaturated fatty acid status and aggression in cocaine addicts.  Drug Alcohol Depend 71(3):319-23.

Fontani G, Corradeschi F, et al (2005). (See two papers, Chapter 3)

Gesch CB, Hammond SM, et al (2002). Influence of supplementary vitamins, minerals and essential fatty acids on the antisocial Behaviour of young adult prisoners. Randomised, placebo-controlled trial.  Br J Psychiatry 181:22-28. 

Hallahan B, Hibbeln JR, et al (2007). Omega-3 fatty acid supplementation in patients with recurrent self-harm. British J Psychiatry 190: 118-22.

Hibbeln Hibbeln JR, Umhau JC, et al (1998). A replication study of violent and nonviolent subjects: cerebrospinal fluid metabolites of serotonin and dopamine are predicted by plasma essential fatty acids.  Biol Psychiatry 44(4):243-49. 

Hibbeln JR (2001). Seafood consumption and homicide mortality.  A cross-national ecological analysis.  World Rev Nutr Diet 88:41-46. 

Hibbeln JR, Nieminen LR and Lands WE (2004). Increasing homicide rates and linoleic acid consumption among five Western countries, 1961-2000. Lipids 39(12): 1207-13.

Hibbeln

Iribarren C, Markovitz JH, et al (2004). Dietary intake of n-3, n-6 fatty acids and

fish: relationship with hostility in young adults—the CARDIA study. Eur J Clin Nutr 58: 24–31.

Kalmijn S, Feskens EJM, et al (1997). Polyunsaturated fatty acids, antioxidants, and cognitive function in very old men. Am J Epidem 145(1): 33-41.

Kalmijn S, van Boxtel MPJ, et al (2004). Dietary intake of fatty acids and fish in relation to cognitive performance at middle age. Neurology 62: 275-80.

Virkkunen ME, Horroboin DF, et al (1987). Plasma phospholipid essential fatty acids and prostaglandins in alcoholic, habitually violent and impulsive offenders. Biol Psychiatry 22: 1087-96.

Virkkunen M, Rawlings R, et al (1994). CSF biochemistries, glucose metabolism, and diurnal activity rhythms in alcoholic, violent offenders, fire setters, and healthy volunteers.  Arch Gen Psychiatry 51(1):20-27.

Weidner G, Connor SL, et al (1992). Improvements in hostility and depression in relation to dietary change and cholesterol lowering.  Ann Int Med 117: 820-23.

Zanarini MC and Frankenburg FR (2003). Omega-3 fatty acid treatment of women with borderline personality disorder: a double-blind, placebo-controlled pilot study. Am J Psychiatry 160:167-69.

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