Should you eat more fish or not? That depends on your age. A report last week warned that women of child-bearing age should avoid eating certain large fish, including swordfish and shark, because the amounts of mercury they contain, though safe for adults, could readily harm children and the unborn. But if you are older, it's a different fish story. A paper published today in the Journal of the American Medical Association advises that middle-aged women should eat more fish to offset the risk of thrombotic stroke. Such strokes are caused by a clot built up on the wall of a brain artery. We observed a significant inverse association between fish intake and risk of stroke, primarily thrombotic stroke, after adjustment for cardiovascular risk factors and selected dietary variables, the authors write. Compared with women who ate fish less than once per month, those with higher intakes of fish had a lower risk of total stroke.
Hiroyasu Iso of Brigham and Womens Hospital and Harvard Medical School and colleagues base their recommendation on a study that followed 79,839 women from 1980 to 1994. The women, who ranged in age from 34 to 59 years old at the beginning of the 14-year study, were all enrolled in the Nurses Health Study. After adjusting for age, smoking and other cardiovascular risk factors, the scientists found that women who ate fish one to three times per month had a 7 percent lower risk of stroke than those who ate fish less than once a month. Women who ate fish once a week had a 22 percent risk reduction; those who ate fish two to four times a week had a 27 percent lower risk; and those who ate fish five or more times per week had a 52 percent lower risk.
The benefits were particularly dramatic in women who did not regularly take aspirin, which itself has been credited with lowering the risk of stroke. And not surprisingly, the researchers found no link between fish consumption and the likelihood of suffering a hemorrhagic strokewhich is caused not by a clot but instead when a blood vessel in or near the brain ruptures. The authors believe the lowered stroke risk comes from n3 fatty acids in the fish that can reduce the aggregation of blood components called platelets. High-dose supplementation of n3 fatty acids also lowers blood pressure levels in hypertensive persons, and reduces plasma fibrinogen concentrations in healthy volunteers, they write. These effects may contribute to the prevention of atherosclerotic development and the thrombotic process.