Objectives: To determine the effects of a vegetarian diet on daytime ambulatory (Accutracker) blood pressures and heart rates, and to relate these to the estimated peak in plasma glucose to determine whether low-glycaemic-index diets reduce sympathetic activity in response to differences in postprandial glucose and insulin.
Design: The subjects were matched for age and body mass index and randomly assigned to one of two parallel diet groups.
Setting: Clinical.
Participants: Twenty-one normotensive non-vegetarian male hospital workers volunteered for the study and 20 completed it.
Intervention: After 2 weeks of baseline measurement the subjects followed an omnivorous or a lacto-ovovegetarian diet for 6 weeks.
Main outcome measures: Daytime ambulatory blood pressures and heart rate, and postbreakfast catecholamines, insulin and glucose.
Results: Ambulatory systolic blood pressure and heart rates were lower in the vegetarian group during the working day. The preprandial rise in diastolic pressure was attenuated on the vegetarian diet. There were no differences in plasma catecholamine, glucose or insulin levels sampled after breakfast on the two dietary regimes.
Conclusions: The blood pressure-lowering effect of a lacto-ovovegetarian diet, which occurs throughout the working day, is associated with lower heart rates, suggesting a central nervous or cardiac mechanism. The possibility that the lower glycaemic index of a lacto-ovovegetarian diet has some effect needs to be investigated further in relation to major meal-times and studied in both normotensive and hypertensive subjects.