
| Summaries of the latest research concerning the health benefits of fish and fish oil |
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Attention deficit hyperactivity disorder (ADHD) - an omega-3
deficiency?
Fish oils may help prevent esophageal cancer Research has shown that colon cancer is associated with an increased expression of the COX-2 enzyme in the colon and that fish oil can reduce both the COX-2 level and the risk of colon cancer. There is also evidence that the COX-2 enzyme is upregulated in Barrett's esophagus and esophageal cancer. British researchers therefore reasoned that fish oil supplementation might also be beneficial in BE and thus, indirectly, lower the risk of esophageal cancer. Their clinical trial involved 46 patients with previously diagnosed BE. Twenty-seven of them were assigned to receive 3 EPA (eicosapentaenoic acid) capsules daily providing a total EPA intake of 1.5 grams a day with the remaining 19 patients serving as controls. Before the start of supplementation and at the end of the 6-month trial period, all participants underwent endoscopy during which appropriate biopsy samples were obtained. Analysis of the samples showed a significantly increased concentration of EPA and a significantly decreased level of COX-2 proteins in BE tissue in the supplement group, but not in the control group.
The researchers conclude that regular supplementation with relatively small doses of EPA results in significant
incorporation of metabolically active long-chain amoega-3 fatty acids into BE tissue and a concomitant, beneficial
decrease in COX-2.
Fish oils in anger management The double-blind, randomized trial involved 24 patients who had a lifelong history of aggressive behaviour and problems with the law, and had been admitted to substance abuse clinics. The average age of the patients was 51 years, 80% were unemployed, and 60% were either separated, divorced or widowed. Eight patients (4 in the treatment group and 4 in the placebo group) had a history of assaultive behaviour and 7 patients in each group had served jail sentences for various offences. Baseline fish intake was low at 36 grams a day average yielding about 150 mg/day of long-chain omega-3 fatty acids, predominantly EPA and DHA. The researchers made the interesting observation that patients with a history of assaultive behaviour consumed only about half the amount of fish consumed by those who had not exhibited this behaviour.
The study participants were randomly assigned to receive placebo capsules (soybean oil) or 5 fish oil capsules a
day providing a total of 2250 mg/day of EPA and 500 mg of DHA. All capsules contained vitamin E as an
antioxidant and lemon oil to mask their taste. At the end of the 3-month supplementation period, the anger score in
the group of patients given fish oil had dropped by over 50% and this improvement persisted for another 3 months
after ceasing supplementation. The anger score for those given the placebo did not change. The researchers
speculate that the beneficial effects of fish oils may be due to their ability to improve membrane fluidity and increase
brain levels of serotonin. They suggest that fish oil supplementation should be considered in treatment protocols for
patients displaying aggressive behaviours.
Fatty acid profile affects birth weight The study involved 3704 pairs of mothers and newborn infants enrolled in the Amsterdam Born Children and their Development (ABCD) study. All mothers completed food frequency questionnaires and gave blood samples around week 12 of their pregnancy. Analysis of the phospholipid phase of blood plasma revealed that mothers with low concentrations of omega-3 fatty acids and the omega-6 fatty acid, DGLA (dihomo-gamma-linolenic acid or eicosatetraenoic acid) gave birth to infants with significantly lower birth weights. Women with high levels of other omega-6 fatty acids and the main trans-fatty acid found in the diet, elaidic acid, also gave birth to infants with lower birth weights. Similar associations were found for SGA.
After adjusting for possible confounding variables, the researchers conclude that low maternal plasma
concentrations of eicosatetraenoic acid, eicosapentaenoic acid (EPA) and DGLA, and high concentrations of
arachidonic acid are associated with reduced fetal growth, lower birth weight, and a 40-50% increase in risk of SGA.
They suggest that the established beneficial effect of fish oil supplementation (EPA and DHA) on pregnancy
duration, in combination with their own results, points to the importance of fatty acid supplementation as a
preventive option at all phases of pregnancy.
Fish oils and arrhythmias The effect of oily fish consumption or fish oil supplementation on atrial fibrillation is less clear. One study involving 4815 men and women 65 years or older (mean age of 73 years) found that consumption of baked or broiled fish was associated with a significantly reduced risk (31%) of developing AF over a 12-year follow-up period. In contrast, a study involving 48,000 much younger people (mean age of 56 years) found an increased risk (34%) of AF with increased fish consumption over a 5.7-year follow-up period. A randomized trial of fish oil supplementation (850 mg EPA+DHA) prior to bypass surgery found that 15% of patients randomized to fish oil developed post- procedure AF as compared to 33.3% in the control group. The researchers suggest that the reason for the discrepancy between the results of the trial involving older people and the one involving younger people could well be that fish oils tend to increase parasympathetic (vagal) tone and this could be detrimental in younger people, while it may be beneficial in older people where sympathetic (adrenergic) tone tends to dominate. Older people would also be more likely to have systemic inflammation and atrial fibrosis which may be reduced by a high intake of long-chain omega-3 fatty acids.
Dietary supplementation with long-chain omega-3 fatty acids (fish oils) is known to change the composition of lipid
membranes toward greater fluidity. There is also evidence that fish oil supplementation inhibits a number of
sodium, potassium and calcium channels in a beneficial way and reduces the production of pro-inflammatory
thromboxanes – all actions that could reduce the incidence of cardiac arrhythmias.
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