OSLO, NORWAY. High blood levels of triglycerides and fibrinogen are known risk factors for cardiovascular disease. Fibrinogen is a large protein molecule which is a key factor in blood coagulation. High levels of fibrinogen aggravate the symptoms of intermittent claudication and speeds up the progression of atherosclerosis. Recent research has shown that fibrinogen level is a more reliable indicator of heart disease risk than is total cholesterol level.
Researchers at the University of Oslo now report that fish oil supplementation is effective in lowering both triglyceride and fibrinogen levels. Their study involved 64 healthy men between the ages of 35 and 45 years. The participants were randomly assigned to receive either 14 1-gram capsules of fish oils or 14 1- gram capsules of olive oil every day for six weeks. The fish oil capsules contained 25.7% eicosapentaenoic acid (EPA) and 20.5% docosahexaenoic acid (DHA) and the olive oil capsules contained about 80% oleic acid. Blood samples were taken and analyzed at the start of the study, 3 and 6 weeks into the study, and 3 weeks after stopping supplementation. The red blood cell (phospholipid phase) content of EPA increased markedly after supplementation; DHA level increased slightly and the level of both linoleic acid and arachidonic acid decreased significantly. Blood level of fibrinogen dropped an average of 13% (from 2.73g/L to 2.37 g/L) after 3 weeks, but returned to baseline 3 weeks after stopping fish oil supplementation. There were no changes in fibrinogen levels in the olive oil group. Triglyceride levels decreased by an average of 22% (from 1.58 mmol/L to 1.23 mmol/L) after 6 weeks in the fish oil group, but increased by about 19% in the olive oil group. Values in both groups reverted to baseline 3 weeks after ceasing supplementation. Total cholesterol level and the level of LDL cholesterol (low-density lipoprotein) did not change with supplementation in either group, but a small transient decrease in the level of HDL (high-density lipoprotein) cholesterol was noted in the fish oil group. Blood pressure fell slightly in both groups after 3 and 6 weeks of supplementation, but reverted to baseline once supplementation was discontinued.
The researchers conclude that the antithrombotic (blood clot preventing) effect of fish oils may be due to their ability to lower fibrinogen levels.
Flaten, Hugo, et al. Fish-oil concentrate: effects of variables related to cardiovascular disease. American Journal of Clinical Nutrition, Vol. 52, 1990, pp. 300-06