Fish and fish oil intake: effect on haematological variables related to cardiovascular disease.

To investigate the effects of practical amounts of n-3 highly-unsaturated fatty acids (HUFA) on a number of parameters involved in haemostasis, 12 healthy men were fed three diets in a 3 x 3 cross-over design. The diets, fed as the evening meal for 6-week periods, were: Control diet (essentially fish-free), Fish diet (200 g/d of lean Australian fish flesh) and the same fish-based diet but supplemented with 5 g/d fish oil (Fish + Oil). The diets supplied about 0, 0.6, and 2.0 g n-3 HUFA/d, respectively. Relative to the Control diet, the number of circulating leukocytes was significantly reduced after both the Fish and Fish + Oil diets (by 13% and 15%, respectively). This reduction occurred in the number of neutrophils, although this did not reach significance on the Fish diet alone. Platelet count fell on the Fish + Oil diet (by 6%) but not on the Fish diet alone. There was an apparent enhancement of fibrinolytic potential after both fish-containing diets, which tended to be accentuated with the fish oil supplementation. The mechanisms underlying some if not all of these observations may be eicosanoid-mediated as indicated by a diminution in the platelet arachidonic acid (20:4n-6) to eicosapentaenoic acid (20:5n-3) ratios after the Fish + Oil (13.7 +/- 1.8) and Fish (34.4 +/- 8.9) diets relative to the Control diet (66.1 +/- 15.6). These data suggest that a practical amount of lean fish can improve certain haematological parameters implicated in the etiology of cardiovascular disease.