DFA: EPA/DHA and Cognitive Health (2011)


Fontani G, Corradeschi F, Felici A, et al. Cognitive and physiological effects of omega-3 polyunsaturated fatty acid supplementation in health subjects. Eur J Clin Invest. 2005; 35(11): 691-699.

PubMed ID: 16269019
Study Design:
Randomized Controlled Trial
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Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

To examine the effects of Omega-3 fatty acid supplementation on some cognitive and physiological parameters in healthy subjects.

Inclusion Criteria:
  • Males and females
  • Healthy subjects
  • Only subjects in good health, free of drugs and medications and with negative psychiatric and endocrine histories were enrolled in the experiment. Moreover, they must have performed non-competitive athletic activities for four hours weekly (aerobic activity, range three to six hours).


Exclusion Criteria:
  • Heavy smoking (more than eight cigarettes per day)
  • Drinking (more than two glasses of spirits per day)
  • Caffeine consumption (more than two cups of coffee per day).
Description of Study Protocol:


  • Subjects were recruited from members of the local non-competitive athletic associations
  • The experiment was carried out on 33 healthy voluntary subjects comprising 13 males and 20 females in the age group 22 to 51 years (mean 33±7 years). 


  • The subjects were randomly assigned to either the Omega-3 or P groups and consumed Omega-3 or P in a blind manner.The subjects were all tested and received a daily supplementation of Omega-3 for 35 days. Omega-3 group consumed eight capsules (4g) of fish oil (FO; 2.8g of Omega-3 PUFAs, EPA + DHA in a ratio of 2.1 and 1.60g of EPA, 0.80g of DHA, 0.40g of other types of Omega-3 PUFAs: Alpha linolenic, stearidonic, eicosatetraenoic and docosapentaenoic acid), while the 16 subjects of P group consumed eight capsules (4g) of olive oil (P) per day.
  • Similarly, a group of 16 subjects (four males and 12 females, mean age 33±3 years) was tested with the same experimental procedure and received a daily a supplementation of olive oil, considered as placebo (P), for 35 days
  • Subjects were tested at the beginning of the experiment and after 35 days
  • Blood samples were taken on day one and day 35 to analyze the specific parameters: Arachidonic acid/eicosapentaenoic acid ratio (AA/EPA), cholesterol, triglycerides, high density lipoprotein (HDL), low density lipoprotein (LDL) and glycemia
  • Tests involving different types of attention were used, i.e., Alert, Go/No-Go, Choice and Sustained Attention
  • The subjects filled in a diary card to record their psychological and mood state and other general information
  • For each test, the reaction time, the event-related potentials by electroencephalogram (EEG) and the electromyography (EMG) of the forefinger flexor muscle were recorded. The subjects then completed the Profile of Mood States (POMS) questionnaire and performed a series of attentional tests with concomitant recording of physiological activities, i.e., electroencephalogram (EEG), electromyography (EMG) and electrocardiogram (ECG).
  • The subjects filled in the Profile of Mood States (POMS) psychometric scale [46] to assess their psychological state. Mood states are temporary and subjects had to report the mood state of the last five days. The POMS consisted of five negative mood scales:
    • Anger (lowest possible value, 40; highest possible value, 99)
    • Anxiety (34 to 85)
    • Fatigue (88 to 37)
    • Confusion (32 to 92)
    • Depression (41 to 91)
    • One positive scale: Vigor (24 to 75).       

Blinding Used

Blinding is used to randomize the subjects.

Statistical Analysis

  • Daily supplementation of olive oil as placebo and omega-3 polyunsaturated fatty acids as active supplement for 35 days
  • Omega-3 group consumed eight capsules (4g) of fish oil and subjects of placebo group consumed eight capsules (4g) of olive oil (P) per day
  • Data from the various tests and biological measures were collected, averaged and then compared by a paired samples T-test for comparison within the same group and a T-test for independent values when comparing between different groups
  • Descriptive statistical analyses were used to define the characteristics of the population studied
  • The associations between the primary measures of interest and cofactors (age and gender) were addressed by ANOVA statistical model
  • Correlations were measured by Pearson’s R-test.


Data Collection Summary:

Timing of Measurements

Baseline and at the end of 35 days.

Dependent Variables

Profile of Mood States (POMS); attention tests.

Independent Variables

Age and gender.


Description of Actual Data Sample:
  • Initial N: 33 healthy voluntary subjects comprising 13 males and 20 females
  • Attrition (final N): 33
  • Age: 22 to 51 years (mean 33±7 years) 
  • Ethnicity: Italians
  • Other relevant demographics: Habits, health, diet, sleep, smoking, use of drugs, alcohol and caffeine, sport activity and work
  • Location: Local non-competitive athletic associations, Italy.
Summary of Results:

Key Findings

  • No association was found between the variables studied and age or gender of subjects. AA/EPA was strongly affected by Omega-3 treatment.
  • The groups Omega-3 and P did not differ at day one (mean values: 16.39±8.32 vs. 16.17±10.63)
  • Comparisons between day one and day 35 in each group, after P and after Omega-3 supplementation, revealed a strong decrease of AA/EPA after Omega-3 [mean values, before Omega-3 (14.26±8.87) and after Omega-3 (4.29±2.60) T=6.89; P<0.0001], while no significant differences were observed after P
  • Other blood parameters did not show significant variations
  • Supplementation with Omega-3 PUFAs was associated with a clear variation of the profile of mood state
  • The POMS analysis showed an increase of vigor and a decrease of the other mood states (anger, anxiety, fatigue, depression, confusion)
  • Vigor and the other mood states did not differ from the period preceding the olive oil supplementation
  • The reaction time (RT) decreased only after Omega-3 supplementation. This reduction occurred in Go/No-Go and Sustained Attention test, but no significant effects were observed in the Alert and Choice tests.
  • The effect was particularly evident in the Sustained Attention test and the reduction of RT appeared to have been distributed over the entire test period with a concomitant reduction of variability after Omega-3 supplementation
  • There was also a significant reduction in the number of errors from a mean of four to two errors/test after Omega-3 (P<0.04)
  • The decrease of RT after Omega-3 supplementation could have been owing to a reduction of the latency of EMG activation of the forefinger flexor muscle engaged in pressing the computer key (time from onset of the stimulus to beginning of EMG activation N= EMG latency), or to an increase in the speed of contraction of the same muscle (time from the beginning of EMG activation to RT).
  • The latter measurement did not show any significant variation the EMG latency was reduced in Go/No-Go, Choice and Sustained Attention tests after Omega-3 supplementation
  • The event-related potentials showed no significant variations during Alert, Choice and Sustained Attention tests, while a change in the wave amplitude occurred in the Go/No-Go test after Omega-3 supplementation
  • There was an increase in amplitude for the negative wave preceding the stimulus (CNV) and for P3, the positive peak after the stimulus
  • The negative peak of the pre-stimulus wave passed through -30μV to -60μV after Omega-3 (P<0.0003)
  • The P3 positive peak recorded before and after Omega-3 supplementation showed an increase in the amplitude in both the Go trial [peak amplitude mean values: before Omega-3 (43.77±42.80μV) and after Omega-3 (84.27±75.23μV); T=2.46; P<0.02] and No-Go trial [peak amplitude mean values: before Omega-3 (37.40±35.23μV) and after Omega-3 (75.65±69.28μV); T=2.40; P<0.02]
  • In particular, after Omega-3 the percentage of the beta-2 band decreased significantly in all the tests and in the relaxation period. Its reduction was accompanied by a concomitant increase of the theta and alpha bands.
  • The analysis of possible relationships between the variation of frequency percentage and other physiological parameters revealed a positive correlation between the theta band percentage in the Sustained Attention test and the vigor state recorded in POMS
  • The results of the POMS questionnaire showed an enhanced vigor state and a concomitant decrease of the negative mood states after Omega-3 supplementation.
Author Conclusion:
  • The results of this experiment revealed an influence of Omega-3 on the activity of the central nervous system
  • This was shown by the improvement of reactivity, attention and cognitive performances in addition to the improvement of mood state and the modifications of some neuro-electrical parameters
  • These results have been obtained from a small study group and need further confirmation in a wider group of subjects and in particular for the possible influences of age and gender
  • The absence of association between the variable studied and age or gender, observed in the present experiment, may be owing to the limited number of subjects
  • It may be assumed that the importance of these results is strengthened by the fact that they occur in subjects in good health and performing physical activity in whom Omega-3 fatty acids improve an already good condition of well-being.
Funding Source:
supplied supplements
Pharmaceutical/Dietary Supplement Company:
Reviewer Comments:
  • A very small study and study duration is only 35 days
  • It is not a double blind trial
  • The pilot study results are showing positive impact of omega 3 fatty acids and an improvement of reactivity, attention and cognitive performances in addition to the improvement of mood state and the modifications of some neuro-electrical parameters in healthy subjects
  • Further studies are required in a large population including EPA, DHA and the ratio of EPA/DHA and AA/EPA on mood state and other neuro-electrical parameters.
Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? N/A
  2.4. Were the subjects/patients a representative sample of the relevant population? No
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? No
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? N/A
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? Yes
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) ???
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? ???
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? N/A
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? N/A
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? ???
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? N/A
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? No
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? No
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? N/A
  10.1. Were sources of funding and investigators' affiliations described? N/A
  10.2. Was the study free from apparent conflict of interest? N/A