Comparison of the effects of two diets rich in monounsaturated fatty acids differing in their linolenic/alpha-linolenic acid ratio on platelet aggregation.
Comparison of the effects of two diets rich in monounsaturated fatty acids differing in their linolenic/alpha-linolenic acid ratio on platelet aggregation.
Year: 1994
Authors: R Freese, M Mutanen, L M Valstra, I Salminen.
Publication Name: Thrombosis and Haemostasis.
Publication Details: Volume 71; Page 73.
Abstract:
The anti-thrombotic effects of long chain n3 PUFAs (EPA and DHA) have been investigated in several epidemiological and experimental studies. There has been less focus on how ALA, the parent n3 fatty acid, affects platelet function in humans. In addition, a great deal of attention has been paid to the favorable effects of oleic acid in the prevention of coronary heart disease (CHD). Canola oil is rich in oleic acid (58% of total fatty acids) and also contains high levels of ALA (11-13% of total fatty acids). Certain studies have demonstrated that canola oil diets alter platelet function to the same degree as sunflower or safflower oil diets that are rich in the n6 fatty acid, linoleic acid (LA). It is therefore possible that the ALA favorably affects platelet function, however, proportions of saturated (SFA), monounsaturated (MUFA), and polyunsaturated fatty acids (PUFA) were not standardized in these studies. The objective of the present study was to investigate the effects of ALA and LA on platelet aggregation in healthy males consuming diets with standardized amounts of SFA, MUFA, and PUFA. Twenty healthy male subjects aged 20-46 years of age participated in this 24-week randomized cross-over study. The study consisted of two six-week pre-experimental dietary periods, and two six-week experimental dietary periods. For the experimental periods, the diets were supplemented with either canola oil (CO) or Tri-sunflower oil (TSO). During the pre-experimental periods, subjects consumed their own habitual diets. During the experimental dietary protocol, subjects were provided the majority of their fat containing foods (margarine, oil, salad dressing, bread, buns, cakes, pies), but were allowed to consume other foods freely. However, fatty fish and fish oil were excluded from the diets. Both experimental diets were designed to provide similar amounts of SFA, MUFA, and PUFA, but different portions of ALA and LA. Following a six-week pre-experimental period, 10 subjects (group 1) followed the TSO diet for a six-week period (experimental period 1). After a six-week washout period (pre-experimental period 2), they continued with the CO diet for six weeks (experimental period 2). The 10 subjects in group 2 followed the experimental diets in reverse order. Fasting blood samples were collected on two separate mornings, 3-4 days apart at the end of the pre-experimental and experimental periods 1 and 2, and 5 weeks after experimental period 2 for analysis of platelet aggregation. The reactivity of platelets to ADP, thrombin, and collagen was performed using the turbidometric method. Results demonstrated that the difference between intakes of LA and ALA were significant between the two experimental diets. However, aside from a small but significant difference in calculated intakes of total PUFAs (8.3 vs 8.9%), the intake of other nutrients and energy was consistent between the two experimental diets. Platelet aggregation induced by all three ADP concentrations was significantly stronger following the TSO diet compared to the CO diet. The TSO diet enhanced ADP induced platelet aggregation compared to the habitual dietary periods, but no significant differences were observed following the RO diet. The slopes of thrombin-induced aggregation were significantly steeper following the TSO diet compared to the CO diet. Aggregation in response to thrombin was also enhanced from pre-experimental level by the TSO diet versus the CO diet. Consuming the TSO diet also induced stronger aggregations to collagen at the two lowest collagen concentrations compared to the CO diet. Finally, when compared to subjects habitual diets, the TSO diet enhanced platelet aggregation induced by the lowest dose of collagen, while the CO diet did not differ in this respect. This study illustrates that LA and ALA in diets rich in MUFAs differ in their effects on platelet aggregation in man. Importantly, a decrease in platelet aggregation was observed as the ratio of LA to ALA decreased.
