(24-02-06) Improved Mood and Cognition in Healthy People Consuming Fish Oil

A developing aspect of long-chain omega-3 polyunsaturated fatty acids (n-3 LC-PUFAs) is their involvement in various brain functions such as cognition, memory, and attention as well as in clinical states such as depression, Alzheimer?s disease, and age-related macular degeneration. Possible explanations for the neurological effects of n-3 LC-PUFAs have come from recent understanding of how these fatty acids affect brain cells themselves in terms of membrane structure and activity, transmission of nerve signals in brain cell synapses, production of neurotransmitters, and changes in gene expression. This large subject has been reviewed recently.

Many observations relating n-3 LC-PUFAs to brain function have been conducted in patients with various clinical conditions or in laboratory animals. Less is known about their effects in healthy people. There have also been conflicting reports about whether n-3 LC-PUFAs improve mood. To shrink this knowledge gap, Dr. Giuliano Fontani and colleagues at the University of Siena, Italy, conducted a placebo-controlled trial in 49 healthy men and women aged 22 to 51 years (mean age 33) who consumed 4 g/day of fish or olive oil in capsule form for 35 days. Thirty-three participants consumed 2.4 g/day n-3 LC-PUFAs provided as 1.6 g eicosapentaenoic acid (EPA), 0.8 g docosahexaenoic acid (DHA), and 0.4 g/day other n-3 PUFAs and 16 consumed olive oil. All participants were in good health, free of medications, and had no history of psychiatric or endocrine disorders. All exercised at least 4 hours weekly.

All participants underwent a medical examination, the Profile of Mood States test, and four attention tests on the first and 35th days of the trial. The attention tests included assessment of alertness, ability to repress an unsuitable response (go/no-go), choice (the ability to react to different stimuli), and sustained attention (ability to react in the presence of stimuli activating a complex go/no-go program). Several physiological recordings such as electroencephalogram, electromyography, heart rate, and reaction times were recorded during the attention tests.

None of the outcomes measured was associated with the sex or age of the participants. Fatty acid analysis of blood samples confirmed compliance with the treatment and revealed a significant decrease in the ratio of arachidonic acid to EPA from 14.3 at baseline to 4.3 after the experimental period. All components of the mood tests showed significant improvement after the 35-day treatment period in those who consumed fish oil compared with baseline values, while there were no significant changes in the olive oil placebo group. For example, assessment of vigor increased while negative states such as anger, anxiety, fatigue, and depression diminished significantly. This research group previously reported improvements in mood with n-3 LC-PUFA consumption, but others have found no effects.

Reaction times in the attention tests were unaltered in the placebo group, but were significantly reduced in the go/no-go and sustained attention tests in those consuming fish oil.

The authors noted that tests in which reaction times were shorter?go/no-go and sustained attention?were those requiring central processing of information. These findings are consistent with the previous reports linking consumption of n-3 LC-PUFAs with better cognitive performance.

In their paper, the authors discuss how changes in the various electrophysiological measurements taken during the attention tests could relate to improved central nervous system function. More extensive evaluations would be needed to test these ideas. Although the authors conclude that n-3 LC-PUFAs affect cognitive performance and mood, there are some red flags. First, no data are given on changes in individual fatty acids, e.g., arachidonic acid and EPA. Ratios muddle the results because they do not reveal which part of the ratio is affected by an intervention and by how much. Second, more appropriate statistical analysis would have been the comparison of the changes in the fish oil with the placebo group in response to treatment. Finally, it should be noted that these participants exercised considerably more often than most healthy people do and consumed at least four times as much n-3 LC-PUFAs as would be obtained from eating two fatty fish meals a week. Some reconciliation among the various ways to assess mood might clarify the conflicting reports on this aspect of wellbeing. Perhaps Scrooge was deficient in omega-3s!

Fontani G, Corradeschi F, Felici A, Alfatti F, Migliorini S, Lodi L. Cognitive and physiological effects of omega-3 polyunsaturated fatty acid supplementation in healthy subjects. Eur J Clin Invest 2005;35:691-699.

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