Natural Foods Merchandiser

Science Briefs

Fish: Heart Healthy—or Not?
Is fish really such a great catch? Fish contains cardioprotective omega-3 fats, but it also contains mercury, which may cause heart attacks. Two researchers recently came to different conclusions in the same issue of the New England Journal of Medicine.

The first researcher, Eliseo Guallar, M.D., Ph.D., of Johns Hopkins Bloomberg School of Public Health in Baltimore, studied 684 European men age 70 or younger who had been hospitalized with a first heart attack and compared them with 724 healthy men. All the men were analyzed for mercury and the omega-3 fat DHA by way of toenail clippings and buttocks fat samples, respectively. When adjusted for other factors, including DHA, men with the top 20 percent of mercury levels doubled their chances of a heart attack. DHA was protective: After adjusting for mercury and other factors, those with the highest levels lowered their heart attack risk 41 percent. Mercury and DHA levels were correlated, showing fish was the main source of mercury.

The second study, part of the Health Professions Study conducted by Kazuko Yoshizawa from Harvard University, identified 470 American men with coronary heart disease, who were matched with controls. This study found no association between mercury and heart disease, even when controlled for omega-3 fat intake. After the researcher excluded 220 dentists who were exposed occupationally to mercury, high toenail mercury was found to increase heart disease risk by 70 percent. But because of low study numbers, this increase was not statistically significant.

Therefore, Yoshizawa concluded that mercury probably does not affect coronary heart disease. However, it might be advisable to follow the conclusion reached by Gualler: Eat fish for its omega-3 fats, but avoid those likely to contain the most mercury, such as swordfish, king mackerel and shark.

Soymilk Lowers Blood Pressure
Drinking a liter of soymilk a day can lower blood pressure in people with hypertension. That's according to the outcome of a controlled study conducted by Miquel Ricas, M.D., of the University of Zaragoza's School of Medicine in Spain. Ricas studied 40 men and women ages 18 to 70 with mild to moderate hypertension (systolic pressure 140 to 180, diastolic pressure 90 to 110). After a four-week period without medication, the participants were randomly assigned to drink 500 ml twice daily of either skim milk or soymilk with the isoflavones daidzein (63 mg) and genistein (80 mg). In the beginning, average blood pressure in both groups was 155/100. After three months, the milk drinkers' blood pressure had dropped slightly. The soy drinkers reduced their blood pressure by an average of 18 points systolic and 15 points diastolic. Urinary levels of genistein, but not daidzein, were strongly correlated with blood pressure reduction. The response was highly individual, however; only 40 percent of the participants reduced their blood pressure by nine points or more. Genistein may reduce blood pressure by increasing sodium excretion and relaxing blood vessels.

Journal of Nutrition
2002 Jul;132(7):1900-2.

Marilyn Sterling, R.D., is a consultant to the natural products industry and a freelance health writer in Trinidad, Calif.

Natural Foods Merchandiser volume XXIV/number 2/p. 55

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