Mercury, Fish Oil and Heart Attacks
KUOPIO, FINLAND. Finnish researchers provide additional evidence of the protective effects of fish oils. Their recently completed study involved 1871 Finnish men aged 42 to 60 years who were free of coronary heart disease at the beginning of the study in 1984. Ten years later 194 of the men had suffered an acute coronary event (160 heart attacks among them). The men had their blood analyzed for fatty acids at the start of the study. Men with a high level (more than 3.58% of total fatty acids) of the polyunsaturated fatty acids found in fatty fish, docosahexaenoic acid (DHA) and docosapentaenoic acid (DPA), were found to have a 44% lower risk of suffering an acute coronary event than did men with a low level (less than 2.38% of total fatty acids). There was no correlation between the level of eicosapentaenoic acid (EPA) and heart attack risk.
Fish caught in Finnish waters tends to have a high level of mercury so the researchers also measured the hair content of mercury in the study participants. They found that men with a high DHA+DPA level and a low mercury level (less than 2 micrograms/gram) had a 67% lower risk of a coronary event than did men with a low DHA+DPA level and a high mercury content (greater than 2.0 micrograms/gram). The researchers speculate that mercury may contribute to the risk of coronary events by binding selenium in an inactive form so that it cannot support the synthesis of the important antioxidant glutathione peroxidase. They conclude that fish oils reduce the risk of acute coronary events, but caution that mercury in fish could reduce this protective effect.
Rissanen, Tiina, et al. Fish oil-derived fatty acids, docosahexaenoic acid and docosapentaenoic acid, and the risk of acute coronary events. Circulation, Vol. 102, November