BETHESDA, MD—The International Workshop on Omega-3 Fatty Acids, Diabetes and Cardiovascular Risk featured many clinical reports and research reviews. Following are some of the highlights.
GISSI-P Shows Mortality Reduction
The massive GISSI-Prevenzione study showed that omega-3 supplementation at 1 g/d resulted in a 16% reduction in combined cardiovascular deaths compared with placebo in post-infarction patients. Among subjects receiving vitamin E, 300 mg/day, there was an 11% reduction. There did not seem to be any additive effect between omega-3’s and vitamin E in subjects taking both (GISSI Prevenzione Investigators. Lancet 1999;354(9177): 447–455).
The big effect was a 40% reduction in sudden cardiac death, which dropped from 3.3% in the controls to 1.8% in the omega-3 group. Dr. Roberto Marchioli, a GISSI investigator, estimated that to avoid 1 death you would need to treat 164 people with omega 3. This compares favorably to drugs like ramipril or simvastatin.
A Little Fish, A Big Effect
Unpublished preliminary data from the University of Washington’s Cardiovascular Health Study show that CVD-free people who ate more than one serving of fatty fish per week had a hazard ratio for ischemic heart disease of 0.4, meaning a 60% reduction compared with those eating less than one serving, said Dr. David Siscovick. The hazard ratio for non-fatal MI was 0.8, or a 20% risk reduction compared to those not eating fish weekly.
“Boiling it all down, this means a 1% difference in DHA/EPA level, associated with small increases in fish consumption, translated into a 45–50% reduction in fatal ischemic heart disease. Some (omega-3) is better than none. That’s clear. What’s not clear is whether more is better than less.”
Revisiting MRFIT
According to Dr. William Lands, the roughly 6,000 subjects in the “usual care” control group of the MRFIT study, when divided by quintile for omega-3 intake, showed a direct correlation with CVD mortality. “Approximately 60% of subjects had nearly no omega-3 intake at all. The upper quintile had roughly 0.33% of total energy coming from omega-3’s.” The latter had a 40% reduction in CV mortality compared with the other quintiles.
DHA, EPA Can Reverse Arrhythmias
Application of EPA or DHA to rat cardiomyocyte cultures will quickly reverse the arrhythmic effects of cardiotoxins such as cardiac glycosides, ouabain, or elevated calcium levels, said Dr. Alexander Leaf, of Harvard Medical School. “You can induce fibrillation with a 15 volt electrode current and then block this excitatory response with EPA and DHA.”
These observations fit the clinical picture. During an ischemic attack, there is tremendous release of fatty acids. In people who don’t get a lot of omega-3’s, the fatty acids released will be saturated fats which are both pro-ischemic and pro-arrhythmic. The anti-arrhythmic effects of omega-3’s might explain the decreases in sudden cardiac death seen in the GISSI-P study.
