COAGULATION AND FIBRINOLYSIS FACTORS IN HEALTHY-SUBJECTS CONSUMING HIGH STEARIC OR TRANS FATTY-ACID DIETS

The effects of stearic acid (C18:0) and trans fatty acids on variables related to coagulation and fibrinolysis were studied in 80 healthy hu mans average age 29 +/- 9 years. All subjects consumed a baseline diet high in saturated fatty acids, mainly from dairy fat for 5 weeks. Aft er this baseline diet they were allocated either to a diet high (8.7% of energy, En%) in trans fatty acids from partially hydrogenated veget able oil (40 subjects) or a diet high (9.3 En%) in stearic acid (40 su bjects) for 5 weeks. All diets contained 32.2-33.9 En% fat, 14.6-15.8 En% saturated plus trans fatty acids, 12.2-12.5 En% cis-monounsaturate d and 2.9-3.5 En% polyunsaturated fatty acids and 216-250 mg/10 MJ cho lesterol. The fats were mixed into solid foods and almost all daily fo od was provided. In comparison with the baseline dairy fat diet no cha nge was observed in the concentrations of plasma fibrin degradation pr oducts and D-dimers. Also the factor VII coagulant activity (F VII:C), tissue type plasminogen activity (tPA) and plasminogen activator inhi bitor activity (PAI-1) were not affected by the experimental diets. Sm all increase in plasma fibrinogen concentration during the stearic aci d diet was statistically significant (from 3.49 to 3.63 g/l; p = 0.041 ), but probably without any biological significance. Both diets increa sed plasma level of lipoprotein Lp(a). It can be concluded that as far as coagulation and fibrinolysis are concerned there is no need to dif ferentiate between stearic acid or trans monoenoic fatty acids. D-dime rs were also associated with increased risk of future myocardial infar ction, although their level was not an independent predictor when the other risk factors were considered (10). Some dietary factors are know n to influence F VII:C, tPA and PAI-1 activities. The factors affectin g F VII:C are: total fat, cholesterol and fibre (11-13); tPA is affect ed by total fat (11, 13); and PAI-1 is influenced by n-3 fatty acids ( 14) and total fat and fibre (13, 15). The effects of dietary factors o n the levels of D-dimers has not been studied. Stearic acid (C18:0) is considered less harmful for CHD risk than saturated fatty acids with 12-16 carbon atoms, since it does not affect serum total or LDL-choles terol (16-18). Furthermore, when compared with fatty acids with 12-16 chain length, stearic acid diet has been shown to lower F VII:C (15, 1 9). However, an increase in fibrinogen level in healthy subjects on a high stearic acid diet (19), as well as an observation that stearic ac id can provide a contact surface that activates factor VII (20) sugges t that stearic acid can be less favorable in terms of CHD risk than an ticipated based on its effect on cholesterol metabolism. To find out i f there are differences in the effects of trans fatty acids and steari c acid on the variables of coagulation and fibrinolysis we carried out a dietary intervention study in a strictly controlled way, so that be sides stearic acid and trans fatty acids the amounts of cis monounsatu rated and polyunsaturated fatty acids in the diets were kept constant.