Docosahexaenoic acid does not affect aggression of normal volunteers under nonstressful conditions. A randomized, placebo-controlled, double-blind study

Sex-specific effects of dietary fatty acids on saliva cortisol and social behavior in guinea pigs under different social environmental conditions

BACKGROUND

Unbalanced dietary intakes of saturated (SFAs) and polyunsaturated (PUFAs) fatty acids can profoundly influence the hypothalamic-pituitary-adrenal (HPA)-axis and glucocorticoid secretions in relation to behavioral performances. The beneficial effects of higher dietary PUFA intakes and PUFA:SFA ratios may also affect social interactions and social-living per se, where adequate physiological and behavioral responses are essential to cope with unstable social environmental conditions.

METHODS

Effects of diets high in PUFAs or SFAs and a control diet were investigated in male and female guinea pigs after 60 days of supplementation. Plasma fatty acid patterns served as an indicator of the general fatty acid status. HPA-axis activities, determined by measuring saliva cortisol concentrations, social behaviors, and hierarchy ranks were analyzed during group housing of established single-sexed groups and during challenging social confrontations with unfamiliar individuals of the other groups.

RESULTS

The plasma PUFA:SFA ratio was highest in PUFA supplemented animals, with female levels significantly exceeding males, and lowest in SFA animals. SFA males and females showed increased saliva cortisol levels and decreased aggressiveness during group housing, while sociopositive behaviors were lowest in PUFA males. Males generally showed higher cortisol increases in response to the challenging social confrontations with unfamiliar individuals than females. While increasing cortisol concentrations were detected in control and PUFA animals, no such effect was found in SFA animals. During social confrontations, PUFA males showed higher levels of agonistic and sociopositive behaviors and also gained higher dominance ranks among males, which was not detected for females.

CONCLUSIONS

While SFAs seemingly impaired cortisol responses and social behaviors, PUFAs enabled adequate behavioral responses in male individuals under stressful new social environmental conditions. This sex-specific effect was possibly related to a general sex difference in the n-3 PUFA bioavailability and cortisol responses, which may indicate that males are more susceptible to changing environmental conditions, and shows how dietary fatty acids can shape social systems.

The effect of omega-3 polyunsaturated fatty acid supplementation on emotional dysregulation, oppositional behaviour and conduct problems in ADHD: A systematic review and meta-analysis

BACKGROUND

A number of randomised controlled trials report a beneficial effect of omega-3 polyunsaturated fatty acid (n-3 PUFA) supplementation on emotional lability (EL) and related domains (e.g. oppositional behaviour, conduct problems). Given that n-3 PUFA supplementation shows a significant effect on reducing symptoms of attention-deficit/hyperactivity disorder (ADHD) and that EL and related behaviours commonly co-occurs with ADHD, it is important that there is a more conclusive picture as to the effect of n-3 PUFA on these co-occurring clinical domains.

METHODS

Databases (Ovid Medline, Embase, Psychinfo) were searched for trials assessing the effects of n-3 PUFA on EL, oppositional behaviour, aggression and conduct problems. We included trials in children who had ADHD or a related neurodevelopmental disorder.

RESULTS

Of the 1775 identified studies, 10 were included in the meta-analysis. In the primary analyses n-3 PUFA supplementation did not show improvements in measures of EL, oppositional behaviour, conduct problems or aggression. However subgroup analyses of higher quality studies and those meeting strict inclusion criteria found a significant reduction in EL and oppositional behaviour.

LIMITATIONS

A number of treatment effects may have failed to reach statistical significance due to small sample sizes and within and between study heterogeneity in terms of design and study participants.

CONCLUSIONS

These results exclude the possibility of moderate to large effects. They provide suggestive evidence of small effects of n-3 PUFA on reducing EL and oppositional behaviour in subgroups of children with ADHD.

A randomised double-blind placebo-controlled trial investigating the behavioural effects of vitamin, mineral and n-3 fatty acid supplementation in typically developing adolescent schoolchildren

Nutrient deficiencies have been implicated in anti-social behaviour in schoolchildren; hence, correcting them may improve sociability. We therefore tested the effects of vitamin, mineral and n-3 supplementation on behaviour in a 12-week double-blind randomised placebo-controlled trial in typically developing UK adolescents aged 13-16 years (n 196). Changes in erythrocyte n-3 and 6 fatty acids and some mineral and vitamin levels were measured and compared with behavioural changes, using Conners' teacher ratings and school disciplinary records. At baseline, the children's PUFA (n-3 and n-6), vitamin and mineral levels were low, but they improved significantly in the group treated with n-3, vitamins and minerals (P=0·0005). On the Conners disruptive behaviour scale, the group given the active supplements improved, whereas the placebo group worsened (F=5·555, d=0·35; P=0·02). The general level of disciplinary infringements was low, thus making it difficult to obtain improvements. However, throughout the school term school disciplinary infringements increased significantly (by 25 %; Bayes factor=115) in both the treated and untreated groups. However, when the subjects were split into high and low baseline infringements, the low subset increased their offences, whereas the high-misbehaviour subset appeared to improve after treatment. But it was not possible to determine whether this was merely a statistical artifact. Thus, when assessed using the validated and standardised Conners teacher tests (but less clearly when using school discipline records in a school where misbehaviour was infrequent), supplementary nutrition might have a protective effect against worsening behaviour.

Fish consumption and resilience to depression in Japanese company workers: a cross-sectional study

BACKGROUND

Depression is a common disorder that is influenced by psychosocial factors in the workplace. Increasing resilience, the ability to cope with stress in the face of adversity, is considered an important strategy to prevent depression. It has been suggested that consumption of fish, which is a major source of long chain n-3 polyunsaturated fatty acids (LC n-3 PUFA), may prevent depression. However, associations between depression, resilience, and fish consumption have not been documented. The aim of the study is to investigate the association between fish consumption and resilience to depression.

METHODS

Participants were 527 Japanese employees at three worksites of a large company. The Center for Epidemiologic Studies Depression (CES-D) Scale was administered to assess depressive symptoms, and the 14-item Resilience Scale (RS-14) was administered to assess resilience. A self-report questionnaire extracted from the Food Frequency Questionnaire was used to measure fish consumption frequency. Regression analyses were conducted to assess a mediation model based on a statistical analysis framework defined by Baron and Kenny. The indirect association of resilience was calculated with the bootstrapping method. Each analysis was adjusted by age, sex, marital status, work position, and educational background.

RESULTS

The association between fish consumption frequency and total CES-D score was significant (B=-0.94; p=0.011). The association between fish consumption frequency and total RS-14 score was significant (B=1.4; p=0.010), as was association total RS-14 score and the total CES-D score (B=-0.34; p<0.001). When controlling for total RS-14 score, there was no longer a significant association between fish consumption frequency and total CES-D score. The bootstrapping results revealed that significant indirect association though fish consumption frequency and total CES-D score (bias corrected and accelerated confidence interval=-0.83 to -0.13; 95% confidence interval) through total RS-14 score.

CONCLUSIONS

Fish consumption might be associated with resilience to depression. Further studies are needed, particularly double blind randomized placebo controlled intervention trials on the potential preventative effect of LC n-3 PUFA on resilience to depression.

Anger induced by interferon-alpha is moderated by ratio of arachidonic acid to omega-3 fatty acids

OBJECTIVE

Anger worsens in some patients during interferon-alpha (IFN-α) therapy. Elevated anger has also been associated with lower long-chain omega-3 (LCn-3) fatty acid levels. We examined whether fatty acids could influence vulnerability to anger during IFN-α exposure.

METHODS

Plasma arachidonic acid (AA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) levels were determined prior to IFN-α therapy by mass spectroscopy. Repeated-measure analyses examined the relationship between AA/EPA+DHA and the subsequent development of labile anger and irritability in 82 subjects who prospectively completed the Anger, Irritability, and Assault Questionnaire (AIAQ) during the first eight weeks of IFN-α therapy.

RESULTS

Prior to IFN-α therapy, AA/EPA+DHA did not correlate with either labile anger or irritability. Pre-treatment AA/EPA+DHA did correlate with the subsequent maximal increase in labile anger during IFN-α therapy (r=0.33; p=0.005). Over time, labile anger increased more in subjects with above median AA/EPA+DHA ratios (p<0.05). Of the 17 subjects ultimately requiring psychiatric intervention for anger, 14/17 had above-median AA/EPA+DHA ratios (p=0.009). There was also an interaction with the tumor necrosis factor-alpha (TNF-α) promoter polymorphism (A-308G), such that only those with both elevated AA/EPA+DHA and the A allele had increased labile anger (p=0.001). In an additional 18 subjects, we conversely observed that selective serotonin reuptake inhibitor treatment was associated with increased irritability during IFN-α therapy.

CONCLUSION

LCn-3 fatty acid status may influence anger development during exposure to elevated inflammatory cytokines, and may interact with genetic risk for increased brain TNF-α. LCn-3 supplements may be one strategy for minimizing this adverse side effect of IFN-α.

The Role of Essential Fatty Acids in Human Health

Fatty acid research began about 90 years ago but intensified in recent years. Essential fatty acids (linoleic and α-linolenic) must come from diet. Other fatty acids may come from diet or may be synthesized. Fatty acids are major components of cell membrane structure, modulate gene transcription, function as cytokine precursors, and serve as energy sources in complex, interconnected systems. It is increasingly apparent that dietary fatty acids influence these vital functions and affect human health. While the strongest evidence for influence is found in cardiovascular disease and mental health, many additional conditions are affected. Problematic changes in the fatty acid composition of human diet have also taken place over the last century. This review summarizes current understanding of the pervasive roles of essential fatty acids and their metabolites in human health.

A double-blind trial of the effect of docosahexaenoic acid and vitamin and mineral supplementation on aggression, impulsivity, and stress

OBJECTIVES

Although a series of well-designed studies have reported that supplementation with vitamins/minerals and omega-3 fatty acids reduces the incidence of aggressive behavior, to date, the relative contribution and interaction between these nutrients has not been examined. The aim was therefore to consider the relative contribution of supplementation with multivitamins/minerals and/or docosahexaenoic acid (DHA) on laboratory-based measures of aggression, impulsivity, and stress.

METHODS

In a double-blind randomized trial, four groups of young adult men without a history of aggressive or impulsive behavior received a placebo (n = 42), multivitamins/minerals (n = 43), DHA (n = 47) or both (n = 41) for 3 months.

RESULTS

With the Picture-Frustration Task, DHA decreased the display of aggressive behavior. DHA also decreased impulsivity as measured using the GoStop Impulsivity Paradigm that examines the ability to inhibit already initiated behavior. Although a multivitamin and mineral supplement did not influence these measures, it did decrease perceived stress.

CONCLUSIONS

The influence of supplementation on aggression and impulsivity can be conveniently studied in a sample without a history of antisocial behavior, using laboratory-based measures. No evidence was found of a synergistic interaction between vitamins/minerals and DHA.

Effects of nutritional supplements on aggression, rule-breaking, and psychopathology among young adult prisoners

In an earlier study, improvement of dietary status with food supplements led to a reduction in antisocial behavior among prisoners. Based on these earlier findings, a study of the effects of food supplements on aggression, rule-breaking, and psychopathology was conducted among young Dutch prisoners. Two hundred and twenty-one young adult prisoners (mean age=21.0, range 18-25 years) received nutritional supplements containing vitamins, minerals, and essential fatty acids or placebos, over a period of 1-3 months. As in the earlier (British) study, reported incidents were significantly reduced (P=.017, one-tailed) in the active condition (n=115), as compared with placebo (n=106). Other assessments, however, revealed no significant reductions in aggressiveness or psychiatric symptoms. As the incidents reported concerned aggressive and rule-breaking behavior as observed by the prison staff, the results are considered to be promising. However, as no significant improvements were found in a number of other (self-reported) outcome measures, the results should be interpreted with caution.

Nutrition, mood and behaviour: a review

OBJECTIVE

To conduct a critical review of recent empirical research regarding mood, behaviour and nutrition factors including essential fatty acids, macronutrients, micronutrients and food additives.

METHOD

A literature search of databases Medline, PsycInfo, CINAHL and Embase up to October 2008. The search emphasised empirical research published in the last 10 years and also included older literature. Studies in both adults and children were addressed.

RESULTS

Research into omega-3 fatty acids has been substantial but evidence for their potential in treating mood and behaviour is modest. In comparison, there has been much less research into carbohydrate and protein intakes and little evidence for their ability to influence mood and behaviour. Recent trials with food additives suggest their removal from the diet may benefit susceptible children with hyperactivity disorders. Micronutrient supplementation appears to improve mood only in those who were initially deficient in micronutrients.

CONCLUSIONS

More stringent research designs such as longitudinal studies and the use of biologically inert placebos within randomised controlled trials are needed before supplemental use of omega-3 fatty acids to treat disorders of mood and behaviour can be recommended. Caution is advised regarding the indiscriminate use of diets free of artificial food additives in managing hyperactivity disorders, as they may place an undue burden on individuals and their families. Should omega-3 fatty acid supplementation or the elimination of certain food additives be established as effective, they may provide cost-effective, accessible and well-tolerated adjuncts to standard psychiatric treatments for mood and behavioural disturbances.

Is there a role for n-3 long-chain polyunsaturated fatty acids in the regulation of mood and behaviour? A review of the evidence to date from epidemiological studies, clinical studies and intervention trials

Selected biochemical evidence suggests a potential role for n-3 long-chain PUFA (n-3PUFA) in the regulation of mood and behaviour. The present paper reviews the relevant evidence, to date, from epidemiological studies, clinical studies and intervention trials. Most evidence is available investigating a role for n-3PUFA in depression, depressive illness and suicidal behaviour, but work is also available on anxiety and anxiety-related disorders, fatigue and fatigue-related disorders, aggression, hostility and anti-social behaviour, inattention, impulsivity and attention deficit hyperactivity disorder and schizophrenic disorders. For all these aspects of mood and behaviour, the evidence available is currently limited and highly inconsistent, both in terms of study methodology and study findings. There is a clear need for further work in this area.

Associations between increases in plasma n-3 polyunsaturated fatty acids following supplementation and decreases in anger and anxiety in substance abusers

OBJECTIVE

Mounting evidence indicates that low levels of n-3 polyunsaturated fatty acids (PUFAs) play a role in the pathophysiology of a large number of psychiatric disorders. In light of the suboptimal n-3 PUFAs intake due to poor dietary habits among substance abusers and the strong associations between aggression, anxiety and substance use disorders we examined if insurance of adequate intakes of n-3 PUFAs with supplementation would decrease their anger and anxiety scores.

METHOD

Substance abusers (n=22) were assigned to either 3 g of n-3 PUFAs, mainly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) or soybean oil in identically looking capsules. The trial was double-blind, randomized and lasted 3 months. Anger and anxiety scales were administered at baseline and once a month thereafter. Blood samples were collected at baseline and at the end of the trial.

RESULTS

Patients' dietary intakes of n-3 PUFAs fell below recommended levels. Assignment to n-3 PUFA treatment was accompanied by significant decreases in anger and anxiety scores compared to placebo assignment. These changes were associated with increases in plasma levels of both EPA and DHA but an increase in EPA was more robustly correlated with low end-of-trial anxiety scores and an increase in DHA was more robustly correlated with low end-of-trial anger scores.

CONCLUSION

These pilot data indicate that ensuring adequate n-3 PUFA intake via supplementation benefits substance abusers by reducing their anger and anxiety levels. The strong correlations between an increase in plasma EPA and lower anxiety scores and between an increase in plasma DHA and lower anger scores suggests a need for the further exploration of the differential responses to these two n-3 PUFAs in different psychiatric conditions.

Long-chain n-3 polyunsaturated fatty acids decrease feelings of anger in substance abusers

It has been suggested that low levels of n-3 polyunsaturated fatty acids (PUFAs) play a role in the pathophysiology of some psychiatric disorders. In light of the existence of strong associations between high-frequency and high-severity aggressive behaviors and substance use disorders and of our observation that substance abusers have poor dietary habits, the possibility that the administration of supplements of n-3 PUFAs would decrease their anger levels was explored. A lifelong history of aggressive behaviors and problems with the law was obtained in 24 patients. Thirteen patients received on a daily basis capsules containing 3 g of n-3 PUFAs (EPA+DHA). Eleven patients received placebo capsules. The trial was double-blind, randomized, and lasted 3 months. An anger scale was administered at baseline and every month thereafter. Six PUFA group patients and eight placebo group patients were followed for an additional 3 months after treatment discontinuation. Four patients in each group had a history of assaultive behavior. The baseline fish and n-3 PUFA intakes of these eight patients were significantly lower than those of the non-aggressive patients. When given for 3 months, n-3 PUFAs were superior to placebo in diminishing anger scores. Scores remained decreased for 3 months following treatment discontinuation. These data provide further support for emerging evidence indicating that supplementation with long-chain n-3 PUFAs could be beneficial in the treatment of some individuals with aggressive tendencies.

Tissue n-3 and n-6 fatty acids and risk for coronary heart disease events

BACKGROUND

Tissue proportions of long chain n-6 [especially arachidonic acid (AA)] and n-3 fatty acids [FA; eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) acids], or some ratio of these may be markers of risk for coronary heart disease (CHD). The purpose of this paper is to evaluate the published associations between risk for CHD events and tissue n-3 and n-6 FA composition.

METHODS

Case-control or prospective cohort data sets examining the risk for CHD endpoints as a function of tissue FA composition were identified. Effect sizes were computed for case versus control comparisons using standard meta-analytic methods.

RESULTS

Twenty-five studies were included, 18 examining the FA composition of phospholipid-rich and 7 of triglyceride-rich samples. DHA, with or without EPA, was significantly lower in cases than controls in all studies combined, in those with fatal endpoints, in those with prospective designs, and in both tissue types. The only setting where increased AA was associated with case status was in adipose tissue. The AA/EPA ratio in phospholipid-rich samples did not distinguish cases from controls. Lower linoleic acid content was associated with increased risk for non-fatal events.

CONCLUSIONS

The long-chain n-3 FA, especially DHA, were consistently and significantly reduced in patients experiencing CHD events. These findings add further support to the view that long-chain n-3 FA are cardioprotective.

The impact of diet on anti-social, violent and criminal behaviour

The role of diet in anti-social behaviour was considered, paying particular attention to double-blind placebo-controlled trials. Meta-analysis of five well-designed studies found that elimination diets reduced hyperactivity-related symptoms, producing a summary standardized mean difference (SSMD) of 0.80 (95% CI 0.41-1.19). The picture was of children potentially responding to a wide range of food items although the pattern was individual to the child. Supplementation with poly-unsaturated fatty acids decreased violence (SSMD -0.61, 95% CI -0.83 to -0.39) although there was no evidence of an influence on hyperactivity. Three well-designed studies have reported that vitamin/mineral supplementation reduced anti-social behaviour. There are also findings of an association between a tendency to develop low blood glucose and aggression. Many responses to diet were idiosyncratic and involved a wide range of foods interacting with individual differences in physiology. Reactions were not observed in all members of groups chosen because they share a common behavioural designation or diagnosis.

One generation of n-3 polyunsaturated fatty acid deprivation increases depression and aggression test scores in rats

Male rat pups at weaning (21 days of age) were subjected to a diet deficient or adequate in n-3 polyunsaturated fatty acids (n-3 PUFAs) for 15 weeks. Performance on tests of locomotor activity, depression, and aggression was measured in that order during the ensuing 3 weeks, after which brain lipid composition was determined. In the n-3 PUFA-deprived rats, compared with n-3 PUFA-adequate rats, docosahexaenoic acid (22:6n-3) in brain phospholipid was reduced by 36% and docosapentaenoic acid (22:5n-6) was elevated by 90%, whereas brain phospholipid concentrations were unchanged. N-3 PUFA-deprived rats had a significantly increased (P = 0.03) score on the Porsolt forced-swim test for depression, and increased blocking time (P = 0.03) and blocking number (P = 0.04) scores (uncorrected for multiple comparisons) on the isolation-induced resident-intruder test for aggression. Large effect sizes (d > 0.8) were found on the depression score and on the blocking time score of the aggression test. Scores on the open-field test for locomotor activity did not differ significantly between groups, and had only small to medium effect sizes. This single-generational n-3 PUFA-deprived rat model, which demonstrated significant changes in brain lipid composition and in test scores for depression and aggression, may be useful for elucidating the contribution of disturbed brain PUFA metabolism to human depression, aggression, and bipolar disorder.

An adaptogenic role for omega-3 fatty acids in stress; a randomised placebo controlled double blind intervention study (pilot) [ISRCTN22569553]

Background

There is evidence for an adaptive role of the omega -3 fatty acid, docosahexaenoic acid (DHA) during stress. Mechanisms of action may involve regulation of stress mediators, such as the catecholamines and proinflammatory cytokines. Prevention of stress-induced aggression and hostility were demonstrated in a series of clinical trials. This study investigates whether perceived stress is ameliorated by DHA in stressed university staff.

Methods

Subjects that scored ≥ 17 on the Perceived Stress Scale were randomised into a 6-week pilot intervention study. The diet reactive group was supplemented with 6 g of fish oil containing 1.5 g per day DHA, while the placebo group was supplemented with 6 g a day of olive oil. The groups were compared with each other and a wider cross sectional study population that did not receive either active or placebo intervention.

Results

There was a significant reduction in perceived stress in both the fish oil and the placebo group from baseline. There was also a significant between-group difference between the fish oil group and the no-treatment controls in the rate of stress reduction (p < 0.05). However, there was not a significant between-group difference between the fish oil and the placebo group, nor the placebo group and the control group.

These results are discussed in the context of several methodological limitations. The significant stress reductions in both the fish oil and the placebo group are considered in view of statistical regression, an effect likely to have been exaggerated by the time course of the study, a large placebo effect and the possibility of an active effect from the placebo.

Conclusion

There were significant differences (p < 0.05) in the fish oil group compared with no-treatment controls. This effect was not demonstrated in the placebo group. As a pilot study, it was not sufficiently powered to find the difference between the fish oil group and the placebo group significant. Further work needs to be undertaken to conclusively demonstrate these data trends. However, the findings from this research support the literature in finding a protective or 'adaptogenic' role for omega-3 fatty acids in stress.

Polyunsaturated fatty acids in the blood of spontaneously or induced muricidal male Wistar rats

Serum levels of several n-6 and n-3 polyunsaturated fatty acids were compared in male Wistar muricidal (Mu) and non-Mu rats. The Mu behavior was either spontaneous or induced by long-term isolation, feeding with a starch-enriched polyunsaturated fatty acid diet (PUFA+S), water restriction, or adrenalectomy (ADX). Arachidonic acid (ARA) levels were lower in diet-induced (PUFA+S) Mu rats than in their non-Mu controls. Total n-6 fatty acid levels were also lower in spontaneously Mu rats than in spontaneously non-Mu rats. Docosahexaenoic acid (DHA) and total n-3 fatty acids levels were lower in rats with isolation-induced Mu behavior. The n-3/n-6 ratio was higher in spontaneously Mu rats than in spontaneously non-Mu rats. The changes in ARA levels were greater than those in DHA levels, possibly due to the higher blood-brain barrier passage of arachidonic acid. The results were analyzed in the light of recent results showing a role of PUFAs in human and animal behavior.

How blind is double-blind? A study of fish oil versus placebo

The distinctive aftertaste associated with fish oil preparations used in clinical trials of omega-3 fatty acids may weaken the double-blind. This double-blind pilot study was designed to examine whether normal subjects could correctly 'guess' if they were receiving capsules containing concentrated fish oil or capsules of pure olive oil. The informed consent was designed to give subjects ambiguous expectations about what oil they might be receiving to examine whether this would influence their guess. Despite a marked difference in taste experience, there was no significant difference in correct guesses between the two groups. The results suggest that altering subjects' expectations could further improve the validity of the double-blind.

The effect of docosahexaenoic acid on aggression in elderly Thai subjects--a placebo-controlled double-blind study

Docosahexaenoic acid (DHA) administration controls extraggression (aggression against others) in young subjects under psychological stress. However, it is not known whether its administration affects extraggression of elderly subjects. Forty Thai subjects of 50-60 years of age (22 males and 18 females) were recruited from Silpakorn University and nearby villages. They were allocated to the control and DHA groups in a double-blind fashion, and took 10 mixed plant oil capsules and 10 DHA capsules (1.5g DHA/day) for 2 months, respectively. Extraggression was measured with a psychological test (PF Study) at the beginning and end of the study. Just prior to the PF Study at the end of the study, subjects were asked to watch a stressful videotape as a stressor component. The average DHA intake from food was 150-160mg/day. In the group of university employees, extraggression did not change over time with placebo, whereas extraggression significantly decreased (31 +/- 13 to 24 +/- 13%, P = 0.04 by the paired-t test, P = 0.04 by ANOVA). In the group of villagers, there was no significant difference between the control and DHA groups in extraggression. The DHA administration favorably controlled extraggression in at least elderly white-collar workers. The daily intake of 150-160 mg/day of DHA was not enough to control extraggression.

A healthy body, a healthy mind: long-term impact of diet on mood and cognitive function

Certain dietary risk factors for physical ill health are also risk factors for depression and cognitive impairment. Although cholesterol lowering has been suggested to increase vulnerability to depression, there is better support for an alternative hypothesis that intake of n-3 long-chain polyunsaturated fatty acids can affect mood (and aggression). Possible mechanisms for such effects include modification of neuronal cell membrane fluidity and consequent impact on neurotransmitter function. Stronger evidence exists concerning a role for diet in influencing cognitive impairment and cognitive decline in older age, in particular through its impact on vascular disease. For example, cognitive impairment is associated with atherosclerosis, type 2 diabetes and hypertension, and findings from a broad range of studies show significant relationships between cognitive function and intakes of various nutrients, including long-chain polyunsaturated fatty acids, antioxidant vitamins, and folate and vitamin B12. Further support is provided by data on nutrient status and cognitive function. Almost all this evidence, however, comes from epidemiological and correlational studies. Given the problem of separating cause and effect from such evidence, and the fact that cognitive impairment and cognitive decline (and depression) are very likely to be significant factors contributing to the consumption of a poor diet, greater emphasis should now be placed on conducting intervention studies. An efficient approach to this problem could be to include assessments of mood and cognitive function as outcome measures in studies designed primarily to investigate the impact of dietary interventions on markers of physical health.

Administration of docosahexaenoic acid influences behavior and plasma catecholamine levels at times of psychological stress

The purpose of the present research was to clarify the effect of docosahexaenoic acid (DHA) intake on behavior and plasma catecholamines (CA). In Study 1, 42 students took either DHA-rich oil capsules containing 1.5-1.8 g DHA/d or control oil capsules containing 97% soybean oil plus 3% of another fish oil for 3 mon in a double-blind fashion. They took a psychological test (PF Study) at the start and end of the study. This study started at the end of summer vacation and ended just before the final exams. In the control group, external aggression (aggression against others) in PF Study was significantly increased at the end of the study as compared with that measured at the start (+8.9%), whereas it was not significantly changed in the DHA group (-1.0%). In a similar double-blind study (Study 2), we measured external aggression under nonstressful conditions. External aggression slightly decreased in the control group, whereas there were no significant changes in the DHA group. In Study 3 with 14 students, plasma CA were measured at the start and end of capsule administration period of 2 mon. Subjects were under continuous stress of the final exams that lasted throughout the whole study period. The ratio of plasma epinephrine to norepinephrine concentrations was significantly increased in the DHA group (78%), whereas it stayed at the same level in the control group. In Study 4, mice were fed either DHA-deficient diet or -sufficient diet for 4 wk, and their rearing frequency (an anxiety index) was measured. In the DHA-sufficient group, the rearing frequency was significantly less than in the other group. These effects of DHA intake may be applied to people in an attempt to ameliorate stress-related diseases.