Do Certain Fish Increase Heart Disease?
Do Certain Fish Increase Heart Disease?
Dec. 4, 2002 -- Eating fish high in omega-3 fatty acids is widely believed to protect the heart, but new research suggests that the mercury in certain types of fish may counteract the beneficial effects of omega-3.
The first study, from Baltimore's Johns Hopkins Medical Institutions, shows that raised mercury levels associated with fish consumption are directly associated with an increased risk of heart attack. But new research from Boston's Harvard School of Public Health shows a weak association at best. Both studies appear in the Nov. 28 issue of TheNew England Journal of Medicine.
The findings come just one week after the American Heart Association published new guidelines on fish consumption. The AHA scientific statement noted that for those at highest risk for heart disease, the benefits of fish consumption within government recommendations "far outweigh the risks." The AHA dietary council recommends the consumption of at least two servings of fish per week, particularly fatty fish high in omega-3 fatty acids.
"These recommendations are based on a substantial amount of data suggesting that populations with higher fish intake have a lower incidence of heart disease," AHA nutrition committee chairman Robert Eckel, MD, tells WebMD. "But [the Johns Hopkins study] is a curveball. Until now nobody has really taken a close look at mercury content in relation to heart disease."
In the Johns Hopkins study, researchers analyzed toenail clippings from roughly 700 men who had recently had heart attacks and a similar number of men who had not, to determine their mercury levels. Mercury levels were 15% higher in the heart attack patients than in the healthy men. When the benefits of omega-3 fatty acid were considered, men who had the highest levels of mercury were found to be at twice the risk for heart attack as those with the lowest.
"The main source of mercury for these men was fish consumption, but fish is also the main source of protective omega-3," lead researcher Eliseo Guallar, MD, DrPh, tells WebMD. "What we found in this group was that the benefits of getting the omega-3 were counterbalanced by the extra mercury."
Do Certain Fish Increase Heart Disease?
Dec. 4, 2002 -- Eating fish high in omega-3 fatty acids is widely believed to protect the heart, but new research suggests that the mercury in certain types of fish may counteract the beneficial effects of omega-3.
The first study, from Baltimore's Johns Hopkins Medical Institutions, shows that raised mercury levels associated with fish consumption are directly associated with an increased risk of heart attack. But new research from Boston's Harvard School of Public Health shows a weak association at best. Both studies appear in the Nov. 28 issue of TheNew England Journal of Medicine.
The findings come just one week after the American Heart Association published new guidelines on fish consumption. The AHA scientific statement noted that for those at highest risk for heart disease, the benefits of fish consumption within government recommendations "far outweigh the risks." The AHA dietary council recommends the consumption of at least two servings of fish per week, particularly fatty fish high in omega-3 fatty acids.
"These recommendations are based on a substantial amount of data suggesting that populations with higher fish intake have a lower incidence of heart disease," AHA nutrition committee chairman Robert Eckel, MD, tells WebMD. "But [the Johns Hopkins study] is a curveball. Until now nobody has really taken a close look at mercury content in relation to heart disease."
In the Johns Hopkins study, researchers analyzed toenail clippings from roughly 700 men who had recently had heart attacks and a similar number of men who had not, to determine their mercury levels. Mercury levels were 15% higher in the heart attack patients than in the healthy men. When the benefits of omega-3 fatty acid were considered, men who had the highest levels of mercury were found to be at twice the risk for heart attack as those with the lowest.
"The main source of mercury for these men was fish consumption, but fish is also the main source of protective omega-3," lead researcher Eliseo Guallar, MD, DrPh, tells WebMD. "What we found in this group was that the benefits of getting the omega-3 were counterbalanced by the extra mercury."
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