M. Mutanen et A. Aro, COAGULATION AND FIBRINOLYSIS FACTORS IN HEALTHY-SUBJECTS CONSUMING HIGH STEARIC OR TRANS FATTY-ACID DIETS, Thrombosis and haemostasis, 77(1), 1997, pp. 99-104
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.