The effect of fish oil on blood pressure in mild hypertensive subjects: a randomized crossover trial

We conducted a double-blind, crossover trial with 18 healthy, untreated mildly hypertensive subjects to test the effect on blood pressure of 6 or 12 g fish oil/d (50% n-3 fatty acids) as compared with an olive oil placebo. Blood pressure was measured every 6 wk in the clinic and three times daily by subjects using a semiautomated device in their homes. Compliance was determined biochemically. No significant changes in home or clinic blood pressure measurements were noted for either dose after 6 or 12 wk of treatment. Clinic blood pressure after 12 g fish oil/d was slightly lower than after placebo treatment by -0.8/-0.4 mm Hg [95% CI: systolic blood pressure (-4.4, +2.8); diastolic blood pressure (-3.2, +2.4)]. Blood pressure changes were not correlated with compliance, baseline dietary fish consumption, or blood pressure. Moderate doses of fish oil did not have a substantial effect on blood pressure. We conclude that fish oil is not a practical treatment for mild hypertension.