Fish oil reduces blood pressure in those whose levels are raised, according to an analysis of 31 placebo controlled trials involving 1356 people (Circulation, 1993 August, 88: 523-33).
Fish oil users had mean reductions of 3.0/1.5 mm Hg the mercury measurement for blood pressure after taking an average 5g of omega-3 fatty acids.
People taking higher doses had greater reductions which strengthens the case for a cause and effect relation, the report concludes.
Despite its effectiveness in lowering raised blood pressure, fish oil does not appear to affect levels in people without hypertension. Eight of the trials reviewed found it had no effect on healthy subjects, whereas a further 19 concluded that it caused insignificant or limited falls in those with normal blood pressure levels.