There is a lot of evidence that people who eat fish regularly may be at reduced risk of getting heart disease, and some studies have shown that fish oils may lower blood pressure. The ingredients that are thought to be responsible for these benefits are called omega-3 fatty acids. In people who are overweight, the most effective non-drug way of lowering the pressure is to lose weight. An Australian study investigated the effects of eating fish and of losing weight, alone and in combination, in a group of 69 overweight people with mild hypertension. Subjects were allocated to one of four groups: the first was a control group who stayed on their regular diet; the second ate the fish diet, which meant eating one fish meal daily. The fish were chosen to contain a lot of omega-3 fatty acids, and included Greenland turbot, sardines, tuna, and salmon. The third group was allocated to weight loss, and the fourth to fish and weight loss. Blood pressure was measured by 24 hour ambulatory monitoring before and after 16 weeks of the diets.

The average weight lost was 5.6 kg (12.3 pounds), which was accompanied by a decrease of daytime blood pressure of 6 mm Hg systolic and 4 mm Hg diastolic. The changes with the fish diet were bigger (7 and 5 mm Hg), but the biggest changes (13 and 9 mm Hg) were seen with the combination of fish diet and weight loss.

Doctor's comments The blood pressure changes achieved by eating fish, particularly when combined with weight loss, were quite large, and of a size more commonly seen with drugs than with non-drug treatment. Salt restriction does not produce changes of this magnitude. Most dietary interventions require eating less of something, and one of the attractive features of the fish diet is that it is easy to follow.

Where it was published Bao DQ and colleagues. Effects of dietary fish and weight reduction on ambulatory blood pressure in overweight hypertensives. Hypertension1998;32:710