Low omega-3 levels put US service members at risk of poor cognitive flexibility and executive function

By Stephen Daniells

- Last updated on GMT

"We were surprised by the strength of the association between omega-3 levels and cognitive flexibility and executive function" - Dr Dan Johnston
"We were surprised by the strength of the association between omega-3 levels and cognitive flexibility and executive function" - Dr Dan Johnston

Related tags: Omega-3 fatty acid

US Military personal with low omega-3 levels are at a higher risk of reduced cognitive flexibility and executive function, says a new study.

Measuring the omega-3 index of 78 serving US soldiers in Iraq revealed that, while there were no associations between omega-3 levels and anxiety, depression, or sleep, there were strong associations with cognitive flexibility and executive function, according to findings published in Nutritional Neuroscience​.

The researchers measured red blood cell levels of EPA + DHA using the HS-Omega-3 Index by Health Diagnostic Laboratory, Richmond, VA.

“The diminished cognitive reserve observed in the lowest quartile HS-Omega-3 Index might compromise performance of mission essential tasks, specifically those requiring dual-tasking,”​ wrote the researchers, led by Dr Dan Johnston from the Comprehensive Soldier Fitness/Performance, Resilience and Enhancement Program, at the Headquarters of the Department of the Army, in Washington, DC.

“Clearly, ingesting more EPA and DHA can increase the HS-Omega-3 Index, whether from food or fish oil supplements. If it could be shown that a higher omega-3 intake improved executive function and cognitive flexibility, mission effectiveness, and overall military operational and medical readiness should also be enhanced.”

Speaking with NutraIngredients-USA, Dr Johnston said that the researchers were surprised by the strength of the association between omega-3 levels and cognitive flexibility and executive function.

“We discovered that deployed soldiers had much lower levels of EPA and DHA than age-matched group from the general population,” ​said Dr Johnston.

Omega-3 and the military

The US Military has a strong interest in the potential health benefits of omega-3 for service members, particularly for the potential cognitive effects for soldiers in active duty.

A 2011 study published in the Journal of Clinical Psychiatry​ found that male US military personnel on active-duty between 2002 and 2008 with the lowest levels of DHA (docosahexaenoic acid) were at a 62% increased risk of suicide than counterparts with higher levels.

Study details

Dr Johnston and his co-workers recruited 78 personnel from two US military camps for their study. Blood samples were taken and used to measure the HS-Omega-3 Index. The participants also completed a battery of psychosocial and computerized neurocognitive tests to test a variety of measures.

Results showed that the mean omega-3 index was 3.5% for the participants, which is significantly lower than the 4.5% previously reported for people of the same age in the general US population.

“This relatively low HS-Omega-3 Index [of 3.5%], given the deployment setting and likely low content of omega-3 fatty acids in the rations, is perhaps not surprising,” ​wrote the researchers.

There was no association between the omega-3 levels and scores for anxiety, depression, or sleep. There were, however, direct associations with cognitive flexibility and executive function, particularly in the 81% of participants who reported to having poor sleep.

An interesting observation was that people with poor sleep quality but above average omega-3 levels seemed to have a ‘resilience to fatigue’, said Dr Johnston, and had higher cognitive flexibility and executive function scores than sleepy participants with lower omega-3 levels.

The obvious next step was to test the effect of omega-3 supplementation on such people, said Dr Johnston, and such a study has already been performed. Data from this randomized, placebo-controlled trial are currently being analyzed and should be published in a peer-review paper later this year.

“On the basis of our findings and other research, educating Service members to choose foods high in omega-3s and raising the EPA and DHA levels in rations should be considered for general health promotion and possible performance optimization,” ​concluded the researchers.

Source: Nutritional Neuroscience
Published online ahead  of print, doi: 10.1179/1476830512Y.0000000025
“Red blood cell omega-3 fatty acid levels and neurocognitive performance in deployed U.S. Service members”
Authors: D.T. Johnston, P.A. Deuster, W.S. Harris, H. MacRae, M.N. Dretsch

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