COMPARISON OF THE EFFECTS OF 2 DIETS RICH IN MONOUNSATURATED FATTY-ACIDS DIFFERING IN THEIR LINOLEIC ALPHA-LINOLENIC ACID RATIO ON PLATELET-AGGREGATION

The effect of dietary linoleic/alpha-linolenic acid ratio on human pla telet aggregation in vitro was investigated using low-erucic acid rape seed oil and high-oleic acid sunflower oil as the major fat sources. I n a cross-over study 20 healthy male subjects, average age 29 year (ra nge 20-46 yr), followed experimental rapeseed oil (RO) and Trisun-sunf lower oil (TSO) diets after their habitual diet for six weeks. Subject s were provided most of the fat containing foods but were allowed to e at other foods almost freely. Fatty acid compositions of the diets cal culated from dietary records were as follows (saturated/monounsaturate d/polyunsaturated fatty acids): RO diet 12.4/18.6/8.9% of total energy (cn%) (linoleic/alpha-linolenic acid ratio 2.8) and TSO diet 11.8/17. 8/8.3 en% (linoleic/alpha-linolenic acid ratio 28), respectively. Plas ma cholesterol ester fatty acid composition proved compliance to the e xperimental diets. Platelet aggregations induced by ADP (1, 2) and 3 m uM) or thrombin (0. 12, 0.15 and 0. 18 NIH/ml) were significantly enha nced and collagen- (1.5, 2.5 and 5.0 mug/ml) induced aggregation tende d to be enhanced after the TSO dict compared with the RO dict. After t he TSO diet platelet aggregation was enhanced from the level of the ha bitual diets by one thrombin (0.18 NIH/ml), one collagen (1.5 mug/ml) and all three ADP concentrations. The diets had no effect on antithrom bin III activity. Results show that platelet aggregation in vitro decr eases as the ratio of linoleic acid to alpha-linolenic acid decreases in diets rich in monounsaturated fatty acids.