This invention relates to a biological oil composition, preferably obtained from a copepod, most preferably the copepod Calanus finmarchicus and the use thereof to prevent or treat formation of atherosclerotic plaques and hence development of coronary heart disease. The composition comprises the same marine n-3 polyunsaturated fatty acids (PUFAs) generally regarded as being responsible for the anti-atherosclerotic effect of marine oils, namely EPA (C20:5n-3 eicosapentaenoic acid) and DHA (C22:6n-3 docosahexaenoic acid). However, quite unexpectedly, it has been found that the oil composition of the present invention has a remarkably higher ability to prevent formation of atherosclerotic plaques than what can be attributed to EPA and DHA alone, and moreover, unlike EPA and DHA alone it has a notable blood cholesterol lowering effect.
