Mercury, Fish Oils, and the Risk of Myocardial Infarction

The Scientific Paper:

Eliseo Guallar, M Inmaculada Sanz-Gallardo, Pieter Van’t Veer, Peter Bode, Antti Aro, Jorge Gomez-Aracena, Jeremy D. Kark, Rudolph A. Riemersma, Jose M. Martin-Morgeno, and Frans J. Kok for The Heavy Metals and Myocardial Infarction Study Group. New England Journal of Medicine (NEJM) Vol. 347, No. 22, pp 1747-1754. 2002.

Review This Scientific Paper’s Abstract:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db
=PubMed&list_uids=12456850&dopt=Citation

The Purpose of this Study:
To learn if methylmercury increases the risk of a certain type of heart disease.

To learn if methylmercury negates some or all of the beneficial effect(s) of eating fish oil in reducing the risk(s) of some types of heart attacks.

Some Background, Methods, Results, Caveats, and Other Select Points:

• This peer-reviewed, scientific paper of a case-control study was published in 2002.
• These results are based on single measurements of methylmercury and one of the beneficial fatty acids. All of these results may suffer from a non-random selection of people used in this study.
• There are many independent risk factors associated with the risk of heart disease including high blood low-density lipoprotein (LDL-C) levels, low blood high-density lipoprotein (HDL-C) levels, high blood pressure, having diabetes, being overweight or obese, being a smoker, and having a family history of certain types of heart attacks.
• Compared to the men in the control group, the “cases” (men who already had a heart attack) had significantly greater risks for some types of heart attacks including worse cholesterol levels, a weight problem, high blood pressure, diabetes, being a smoker, and having a family history of certain types of heart attacks.
• These scientists did not know: 1) the source(s) of methylmercury (or other forms of mercury these men were exposed to); 2) the source(s) of the beneficial fatty acid studied these men ate; or 3) the amount(s) and/or type(s) of fish these men ate.
• The participation rate for the men who already had a heart attack (“cases” in a case-control study) was higher than for the control group of men who hadn’t yet suffered a heart attack (“controls”). This difference in a willingness and dedication to fully participate throughout the entire study does raise the possibility of some selection bias in choosing the normal men in the control group for this study.
• These scientists conducted this case-control study in eight European countries and in Israel. They looked at the relationship of mercury levels and one of the beneficial fatty acids in the fat of these men. The 684 men studied each had a first diagnosis of a common kind of heart attack. The 724 control men were believed to represent the same populations as the 684 men with a first diagnosis of a common kind of heart attack.

A Bottom Line:
The high methylmercury content of certain fish may reduce the protection afforded to the hearts of men who oftentimes eat those certain fish.

These scientists do not imply that people should stop eating fish. In fact, their study of these men is consistent with a protective effect of eating fish not heavily contaminated with methylmercury.

Find This Scientific Paper for Your Review:
Mercury, Fish Oils, and the Risk of Myocardial Infarction. New England Journal of Medicine (NEJM) Vol. 347, No. 22, pp 1747-1754. 2002.