The effect of a salmon diet on blood clotting, platelet aggregation and fatty acids in normal adult men.

This study was designed to measure the effect of dietary n-3 fatty acids (FA) on platelets and blood lipids. Healthy men (n = 9), ages 31 to 65, were fed diets in which salmon was the source of n-3 fatty acids. They were confined in a nutrition suite at this Center for 100 days. Food intake and exercise levels were rigidly controlled. Initially they were placed on a stabilization diet for 20 days, then six men were fed the salmon diet for 40 days. The others remained on the stabilization diet. The two groups switched diets for the last 40 days of the study. Both diets were isocaloric [16% protein, 54% carbohydrate, and 30% fat by energy-% (En%)]. The salmon diet contained 7.5% of calories from n-6 FA and 2% from n-3 FA, primarily eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in a 40:60 ratio, while the stabilization diet contained 7.5% of calories from n-6 FA and less than 0.3% n-3 FA, mainly 18:3n-3. The bleeding time was unaffected by the diets in this study. The prothrombin time was shortened (11.6 sec. vs. 12.6 sec., p less than 0.01) for the subjects consuming the salmon diet as compared to that measured after 20 days of the stabilization diet. Mean platelet volume increased significantly during the period in which the volunteers consumed the salmon diet compared to the baseline diet (p less than 0.01), while the mean platelet levels decreased. Platelet aggregation (PA) was measured in platelet rich plasma before, during, and after the salmon diet using collagen, ADP, arachidonic acid (AA), and thrombin agonists. The PA threshold for ADP was significantly increased for the subjects on the salmon diet (p less than 0.05). No change in the PA threshold was detected for collagen or thrombin. The PA threshold for AA was unchanged also, but the platelets in subjects consuming the salmon diet had a prolonged time to maximum aggregation (p less than 0.01) with this reagent compared to platelets from men on the stabilization diet. Plasma, red cell, and platelet total FA composition was determined by capillary GLC. While the men consumed the salmon diets, there were marked increases (3 to 10-fold) in the EPA and DHA levels in all blood components with concomitant decreases in linoleic acid and AA levels.(ABSTRACT TRUNCATED AT 400 WORDS)