A STUDY OF THE INTERACTIVE EFFECTS OF ORAL-CONTRACEPTIVE USE AND DIETARY-FAT INTAKE ON BLOOD-PRESSURE, CARDIOVASCULAR REACTIVITY AND GLUCOSE-TOLERANCE IN NORMOTENSIVE WOMEN

Objective To investigate the interactive effects of oral contraceptive pill use and dietary fat intake on cardiovascular haemodynamics and m etabolic parameters in young normotensive women. Design Thirty-two wom en participated, of whom 16 were taking oral contraceptive pills (ethi nyl-oestradiol plus levonorgestrel) and 16 were age-matched and weight -matched controls not taking such pills. Subjects consumed either a hi gh-fat or a low-fat diet for 2 weeks in an open, randomized, crossover study lasting 6 weeks. Investigations were performed at the end of ea ch diet during the luteal phase of the menstrual cycle. Methods Blood pressure was measured by 24 h ambulatory recording; cardiovascular rea ctivity was determined by examining blood pressure responses to system ic infusions of noradrenaline and angiotensin II and to the cold press or test; and carbohydrate metabolism was investigated by an intravenou s glucose-tolerance test. Results Plasma triglyceride levels were sign ificantly higher in women taking oral contraceptive pills compared wit h non-users on both diets; however, responses of lipoprotein levels to the two diets did not differ between study groups (total and low-dens ity lipoprotein cholesterol levels decreased by 15 and 17% in oral con traceptive pill users and by 14% each in nonusers, on the low-fat comp ared with the high-fat diet). Fasting plasma insulin levels, the insul in-production response to administration of glucose (insulin area unde r the curve) and resting clinic and night-time systolic blood pressure s were all significantly reduced on the low-fat diet, but only in non- users. Blood pressure responses to noradrenaline and maximal heart rat e response to cold were significantly attenuated during the low-fat di et in oral contraceptive pill users. During the low-fat diet, resting systolic, 24 h systolic and diastolic blood pressures and insulin area under the curve were all significantly higher for women taking the or al contraceptive pills. Users of these pills also exhibited a greater systolic sensitivity to administration both of noradrenaline and of an giotensin II and had a higher plasma renin activity irrespective of di etary phase. Conclusions These results confirm that oral contraceptive pills have the potential to cause adverse effects on blood pressure, cardiovascular reactivity and the insulin-production response to admin istration of glucose and suggest that some of the beneficial effects o f a low-fat diet on these parameters may be negated in women taking or al contraceptive pills. (C) 1998 Rapid Science Ltd.