Death from coronary heart disease (CHD) (heart attack and chest pain) can be due to heart failure, arrhythmias (abnormally fast or slow heart rhythm) or sudden cardiac death (SCD). Most SCD is due to ventricular fibrillation (abnormal irregular rhythm of the heart where the ventricles i.e. lower chambers of the heart, contract in a very rapid, unsynchronized manner ′fluttering′). The risk of death and sudden death is highest in the first months following a heart attack.
One of the most remarkable benefits of fish oils is their ability to prevent sudden death, SCD in particular. They have antiarrhythmic effect i.e. reducing potentially fatal abnormal heart rhythms, or arrhythmias that lead to SCD and thus offer protection against cardiac sudden death. Fish oil is particularly effective in fighting the common but worrying heart arrhythmia known as atrial fibrillation abnormal heart rhythm that involves the two upper chambers or the atria of the heart. This is especially important, as atrial fibrillation increases the risk of stroke.
More than 2,000 men with previous heart attack were studied to examine the life-saving beneficial action of fish oil. Some were advised to regularly eat fish, while others were not asked to do so. The difference in mortality observed between the two groups after two years was dramatic. Men who consumed fish oil twice a week had a 29% lower rate of death than those who did not. According to the researchers, fish oil helped prevent death in these men with a history of heart muscle damage by stopping the abnormal heart rhythms. Another important study showed that regular consumption of fish is associated with a decrease in heart rate in healthy men. In a study, 9,758 men from Lille (France) and Belfast (Ireland) aged 50-59 years with no previous CHD were grouped according to the amount of fish they consumed on a normal basis.
- 27% ate fish less than once per week
- 47% ate fish once per week
- 20% had fish twice per week
- 6% ate fish more than twice per week
Regular consumption of fish is associated with decreased heart rate in healthy men which lower the chances of sudden death among fish eaters. In men who ate fish less than once per week, the average heartbeat was 67.5 beats/minute, whereas, the average heartbeat was 65.6 beats/minute in men who ate fish more than twice per week. In a small group of patients undergoing cardiac surgery, consumption of fish oil (2 g/day) for at least five days before elective CABG and until the day of discharge from the hospital markedly reduced the incidence of post-operative AF (54.4%) and was associated with a shorter hospital stay. Another study also found an association between fish oil consumption and reduced risk of atrial fibrillation. It has been shown that patients who develop arrhythmias often have low omega-3 fatty acid levels in their blood. This further affirms the usefulness of omega-3 fatty acids supplementation in promoting healthy heart rhythm.
In a group of 84,688 women aged 34-59 years, from the US Nurses′ Health Study, higher consumption of fish and n-3 fatty acids caused fewer deaths. Compared with fish consumption intake of less than once a month, eating fish at least five times a week lessened the risk of overall death by 32%. Compared with the lowest quintile of omega-3 fatty acid intake, the highest quintile was associated with a 25% reduced risk of overall death. The results also suggested that fish consumption is more protective against fatal CHD than nonfatal myocardial infarction. Oily fish consumption was associated with a 34% reduced risk of death due to CHD during 20 years of follow-up compared with no oily fish consumption. Consumption of 15 g/day of lean fish is equal to about 50 mg of omega-3 fatty acids; in contrast, 15 g/day of oily fish provides about 400 mg of omega-3 fatty acids.
The Time-course of Any Benefit Appears Early
In a major clinical study, the GISSI-Prevenzione trial, in patients with recent heart attack, fish oil reduced mortality, entirely due to fewer SCDs. The protective benefits of fish oil were evident after only a few months of supplementation. In this large study of more than 11,000 adults, those who consumed 1,000 mg of EPA and DHA daily (taken as fish oil supplement) had a 42% reduction in SCDs within the three-month period following a heart attack compared to patients who received no omega-3 fatty acids. These life-saving benefits persisted beyond the initial 3-month danger period as evident by a death rate of 8.4% among the participants who had received the fish oil supplement and 9.8% among those who had not received the fish oil supplement by the end of the 42-month follow-up period.