Among the established health benefits of a diet rich in n-3 fatty acids (found in ocean fish as well as in flaxseed oil) is its protective effect aginst cardiovascular diesease. Mori and colleagues at the University of Western Australia have found that overweight patients being treated for hypertension were able to realize significant health improvements--not only in cholesterol levels but also in diabetic symptoms--by incorporating a daily meal of fish into their weight-loss diet. The 69 subjects in the study were characteristically overweight middle-aged men and women being treated with medications for hypertension, who were also at risk for diabetes and had high serum cholesterol levels.
While even small amounts of fish and fish oil have been shown to lower blood pressure and reduce cardiovascular risk, a possible bad side effect of large amounts of fish consumption is impairment of glucose tolerance, or a worsening of diabetic symptoms. The authors were looking for additive or synergistic effects oncholesterol levels and diabetic symptoms when a weight-loss diet was combined with a daily meal including fish. A gratifying result of the study was that the combination method lowered the patients' cholesterol levels, while also having a beneficial effect on their glucose metabolism and promoting successful weight loss. The critical, and positive, difference with this specific regimen was that the fish meals were part of a relatively low fat diet (30% or less of calories from fat), while in a previous study the fat content of the prescribed diet was 40%. The authors hypothesize that the patients' glucose tolderance improved because the fish-plus-weight-reduction-diet regimen might have produced changes in fatty acid delivery to the liver,as a result of the profound reduction in blood lipid levels produced by n-3 fatty acids in combination with a reduction abdominal fat.