A common dietary supplement can reduce aggression by up to 28%

New research suggests that omega-3 supplements could be an effective tool in reducing aggressive behavior. A recent meta-analysis found that omega-3 supplementation can lead to a modest, yet significant reduction in aggression. The findings indicate a potential 28% decrease in aggression across various demographics and settings. The findings have been published in the journal Aggression and Violent Behavior.

The study was driven by a long-standing interest in the connection between nutrition and behavior. Omega-3 fatty acids, found in fish and fish oil supplements, are known to have a positive association with brain function. Omega-3 fatty acids are crucial components of the cell membrane and contribute to various brain activities, including enhancing neuron growth, regulating neurotransmitters and gene expression, and supporting nerve cell signaling. They also reduce brain inflammation and improve cerebral blood flow.

Previous research has shown a link between poor nutrition and behavior problems, including aggression and violence. Given these connections, Raine has been investigating whether omega-3 supplementation could help mitigate aggressive behavior. He has published five randomized controlled trials from different countries with significant findings but wanted to see if these effects were consistent across a broader range of studies.

“We had previously shown that poor nutrition is a risk factor for aggression. We had also conducted an early intervention that included two extra portions of fish each week, and which showed a 34% reduction in criminal offending 20 years later. That put us onto considering omega-3 as an active ingredient in that early intervention,” explained study author Adrian Raine, a professor at the University of Pennsylvania and author of The Anatomy of Violence: The Biological Roots of Crime.

To explore this, Raine conducted a meta-analysis, which is a statistical technique that combines data from multiple studies to look for overall trends. He and his colleague Lia Brodrick analyzed 29 randomized controlled trials that explicitly measured aggression. These studies spanned nearly three decades and included a total of 3,918 participants. The researchers selected studies that met specific criteria: they had to involve human subjects, use omega-3 supplementation, measure aggression directly, and provide enough data to calculate an effect size.

The studies were sourced from seven different databases, including PubMed and Web of Science, and involved a variety of populations, from children to adults and from community samples to clinical populations. The meta-analysis also examined various moderators, such as age, gender, dosage, and treatment duration, to understand how these factors might influence the effectiveness of omega-3 in reducing aggression.

The meta-analysis revealed that omega-3 supplementation leads to a modest reduction in aggression. The overall reduction in aggression was 16.2% when considering independent samples, and this increased slightly to 20.4% and 27.8% when considering independent studies and laboratories, respectively. These consistent percentages suggest that omega-3 supplementation can be broadly effective across various populations and settings.

“We had thought that there would be a dose effect, with greater benefits with increased omega-3, but we did not find that,” Raine told PsyPost. “Even modest supplementation of omega-3 seems to be helpful.”

Interestingly, the study found that omega-3 supplementation was effective for both reactive aggression (impulsive, emotional responses) and proactive aggression (planned, goal-directed behavior).

Another important aspect of the study is the lack of evidence for publication bias. The researchers used statistical tests to ensure that the positive results were not due to selective publication of studies with significant findings. This strengthens the validity of their conclusions and underscores the reliability of the meta-analysis.

The results provide evidence that “increased omega-3, either through supplements or fish, can help reduce aggressive behavior,” Raine said.

While the findings are promising, the study has some limitations. The effect sizes, while significant, are modest, indicating that omega-3 is not a cure-all for aggressive behavior. The study also only looked at short-term effects; more research is needed to determine whether the benefits of omega-3 supplementation persist over the long term.

“Omega-3 is not a panacea for abolishing aggression,” Raine noted. “We estimate that it may reduce aggression by about 30%, so clearly there are a lot of other factors other than nutrition that are involved in aggression.”

Future research could explore the mechanisms by which omega-3 affects aggression. Since omega-3 plays a crucial role in brain function, it is likely that its effects on aggression are mediated by changes in brain structure and function. Neurocognitive assessments, brain imaging studies, and analyses of neurotransmitter functioning could provide valuable insights into how omega-3 supplementation reduces aggression.

“We have shown that omega-3 supplements to prisoners can reduce aggressive and antisocial behavior in prison, but can it reduce recidivism?” Raine said. “We have pilot data showing that it can, but we need long-term randomized controlled trials to test this further.”

“Given the additional psychological and physical benefits of omega-3 supplementation and ease of implementation, we believe the time has come both to execute omega-3 supplementation in practice and also continue to scientifically investigating its longer-term efficacy.”

The study, “Omega-3 supplementation reduces aggressive behavior: A meta-analytic review of randomized controlled trials,” was published online on May 19, 2024.