Mercury, fish oils, and the risk of myocardial infarction.
BACKGROUND
It has been suggested that mercury, a highly reactive heavy metal with no known physiologic activity, increases the risk of cardiovascular disease. Because fish intake is a major source of exposure to mercury, the mercury content of fish may counteract the beneficial effects of its n-3 fatty acids.


METHODS
In a case-control study conducted in eight European countries and Israel, we evaluated the joint association of mercury levels in toenail clippings and docosahexaenoic acid (C22:6n-3, or DHA) levels in adipose tissue with the risk of a first myocardial infarction among men. The patients were 684 men with a first diagnosis of myocardial infarction. The controls were 724 men selected to be representative of the same populations.


RESULTS
The average toenail mercury level in controls was 0.25 microg per gram. After adjustment for the DHA level and coronary risk factors, the mercury levels in the patients were 15 percent higher than those in controls (95 percent confidence interval, 5 to 25 percent). The risk-factor-adjusted odds ratio for myocardial infarction associated with the highest as compared with the lowest quintile of mercury was 2.16 (95 percent confidence interval, 1.09 to 4.29; P for trend=0.006). After adjustment for the mercury level, the DHA level was inversely associated with the risk of myocardial infarction (odds ratio for the highest vs. the lowest quintile, 0.59; 95 percent confidence interval, 0.30 to 1.19; P for trend=0.02).


CONCLUSIONS
The toenail mercury level was directly associated with the risk of myocardial infarction, and the adipose-tissue DHA level was inversely associated with the risk. High mercury content may diminish the cardioprotective effect of fish intake.
Guallar
Eliseo
E
Department of Epidemiology and Welch Center for Prevention, Epidemiology and Clinical Research, Johns Hopkins Medical Institutions, Baltimore, MD 21205-2223, USA. eguallar@jhsph.edu
Sanz-Gallardo
M Inmaculada
MI
van't Veer
Pieter
P
Bode
Peter
P
Aro
Antti
A
Gómez-Aracena
Jorge
J
Kark
Jeremy D
JD
Riemersma
Rudolph A
RA
Martín-Moreno
José M
JM
Kok
Frans J
FJ
D000273:Adipose Tissue / Q000737:chemistry; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D004281:Docosahexaenoic Acids / Q000032:analysis*; D004305:Dose-Response Relationship, Drug; D005227:Fatty Acids / Q000737:chemistry; D006801:Humans; D008297:Male; D008628:Mercury / Q000009:adverse effects* / Q000032:analysis; D008875:Middle Aged; D009203:Myocardial Infarction / Q000139:chemically induced* / Q000517:prevention & control; D009262:Nails / Q000737:chemistry; D012307:Risk Factors
D005227:Fatty Acids; D004281:Docosahexaenoic Acids; D008628:Mercury