CINCINNATI, OHIO. Conventional blood pressure lowering medications often have detrimental effects on quality of life and may lead to unfavourable changes in cholesterol levels. Several studies have found that supplementation with large amounts of fish oil (5-15 grams/day) lowers blood pressure significantly in hypertensive individuals. Whether smaller amounts are equally effective has been open to question.
Researchers at the University of Cincinnati (Ohio) College of Medicine now report that daily supplementation with low doses of fish oil is indeed effective in lowering blood pressure in mildly hypertensive patients. Their study involved 33 patients (men and women) with a diastolic pressure between 90 and 104 mm Hg. After a four-week wash-out period during which the participants discontinued all medications the patients were randomly allocated to one of two groups. Group 1 supplemented with 2.04 grams/day of fish oil containing 410 mg of eicosapentaenoic acid and 285 mg of docosahexaenoic acid. Group 2 was given a placebo capsule daily containing safflower oil (80% linoleic acid). After 12 weeks and a four-week wash-out period the groups switched supplementation so that group 1 now received the placebo. Blood pressure, heart rate, and body weight were recorded at two- week intervals during the study and blood samples were collected and analyzed at the beginning and end of each treatment period.
The researchers found that fish oil supplementation reduced diastolic pressure (sitting) by an average of approximately 4.4 mm Hg and systolic pressure by an average of 6.5 mm Hg when compared to values obtained prior to the start of treatment. There were no adverse effects on cholesterol levels. They conclude that fish oil supplementation is a safe and effective way of lowering blood pressure in mildly hypertensive subjects, but noted that the beneficial effects wear off relatively quickly once supplementation is discontinued.
Radack, Kenneth, et al. The effects of low doses of n-3 fatty acid supplementation on blood pressure in hypertensive subjects. Archives of Internal Medicine, Vol. 151, June 1991, pp. 1173-80