The influence of different types of omega 3 polyunsaturated fatty acids on blood lipids and platelet function in healthy volunteers.

1. Five healthy subjects took a daily supplement of 20 ml of linseed oil for 2 weeks. After a break of at least 6 weeks, the same subjects took a similar amount of MaxEPA (a fish oil fraction) for 2 weeks. The linseed oil supplement provided 9.38 g of linolenic acid (18:3 w3) and the MaxEPA supplement provided 3.03 g of eicosapentaenoic acid (20:5 w3) and 2.93 g of docosahexaenoic acid (22:6 03). The effects of the supplements on plasma lipid concentrations and on the fatty acid composition of platelet phosphoglycerides were studied. 2. In a second experiment, five male subjects took 5 , 10 and 20 g of MaxEPAIday in random order for 3 week periods; each experimental period was separated by a break of at least 6 weeks. These doses of MaxEPA provided 0.83, 1-67 and 3.33 g of 20:5 0 3 and 0.80, 1.61 and 3.22 g 22 :6 w3 respectively. The effects of these supplements on plasma lipid concentrations, the fatty acid composition of platelet phosphoglycerides, template bleeding time and platelet aggregation induced by collagen and the prostaglandin analogue compound U466 19 were studied. 3. In the platelet lipids, the proportion of 20 : 5 w3 was increased by the 20 ml linseed oil supplement but the increase was small compared with the increase brought about by even 5 g of MaxEPAIday. The proportion of arachidonic acid (20:4 w3) was substantially decreased by the MaxEPA supplement but not by the linseed oil supplement. The ratio of 20 :4 ~ 6 1 2 0 : 5 0 3 fell from 32 : 1 in the control periods to 1 1 : 1 with