- The offspring of coronary heart disease (CHD) patients are at particularly high risk for developing CHD. Endothelial dysfunction is present in the majority of CHD and atherosclerosis patients. Fish oil, rich in n-3 fatty acids has been shown to augment endothelium-dependent vasodilatation in human peripheral and coronary arteries. The aims of this study are to investigate presence of endothelial dysfunction determined by the brachial flow-mediated diameter, nitric oxide, plasma lipids and fibrinogen, and the effect of high doses of fish oil on these parameters. Twenty-four healthy offspring of CHD patients (study group) were supplemented with 9 g/day Alsepa fish oil (each gram containing 180 mg EPA and 120 mg DHA), for a period of two weeks. Plasma nitric oxide, urine nitric oxide, fibrinogens and flow-mediated vasodilatation (FMD) were determined prior to fish oil therapy, two weeks into therapy and four weeks after the end of therapy with fish oil. Twelve healthy subjects (control group) with no family history of heart disease were studied as controls (day one only). The offspring had a lower increase in FMD and lower nitric oxide production, compared with the control group. No other parameters varied between the two groups. The administration of fish oil did not result in any changes in the studied parameters. In healthy offspring of CHD patients, early endothelial dysfunction was documented before evidence of atherosclerosis. Ingestion of fish oil over a 13-day period did not improve endothelial dysfunction.