The study led by Jyrki K. Virtanen at University of Eastern Finland, Institute of Public Health and Clinical Nutrition, Kuopio, Finland and colleagues also found this benefit was only found in individuals who had low mercury exposure or mercury exposure cuts the benefit.
Fish consumption has been linked to reduced risk of cardiovascular disease, especially sudden cardiac death. T he protection is believed to be attributed to the long chain n-3 polyunsaturated fatty acids (PUFAs), namely, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
The current study was intended to examine the effect of mercury exposure and serum PUFAs on the risk of sudden cardiac death among 1857 men aged 42 to 60 years of age who were enrolled in the prospective, population-based Kuopio Ischaemic Heart Disease Risk Factor study between 1984 and 1989. Both serum n-3 PUFAs and hair mercury were measured at baseline. During a mean 20 year-follow-up, 91 men experienced sudden cardiac death.
Overall, serum levels of n-3 PUFAs were not associated with risk of sudden cardiac death when the analysis did not consider hair mercury.
When hair mercury was considered, it was found that men in the highest serum levels of n-3 PUFAs were 46 percent less likely to suffer sudden cardiac death, compared with those in the lowest serum levels of n- 3 PUFAs.
Among those with low mercury in their hair, an increase of n-3 PUFAs by 0.5 percentage was associated with 23 percent reduction in the risk of sudden cardiac death.
But among those with high mercury, omega-3 polyunsaturated fatty acids no longer helped reduce the risk.
The researchers also found that DHA was more strongly associated with reduced risk of sudden cardiac death, compared to EPA.
The study suggests that high mercury exposure may offset the protective effect from fish oil against sudden cardiac death.
