Biochemical and neurohormonal responses to the introduction of a lacto-ovovegetarian diet.

OBJECTIVE: To assess the mechanisms of the blood pressure-lowering effect of a vegetarian diet in the early and later stages of dietary intervention. DESIGN: After 2 weeks without intervention (baseline), 20 normotensive men were matched for age and body mass index and randomly allocated to an omnivorous (control) or a lacto-ovovegetarian diet for 6 weeks in a parallel trial. METHODS: Ambulatory blood pressures were recorded between 0800 and 1700 h on alternate days during the first week of intervention, twice in the second week and weekly thereafter. Blood samples collected after a standard breakfast were analysed for plasma noradrenaline, adrenaline, atrial natriuretic peptide (ANP), renin, aldosterone, glucose and insulin. Factor and multiple regression analyses were used to assess the association among neurohormonal factors, blood pressures and diet. Results were analysed for the first week of the diet and for the entire 6 weeks. RESULTS: Ambulatory blood pressures at work were lower on the vegetarian diet than in the controls. This blood pressure decrease was associated with a factor representing lower plasma catecholamine and renin activity levels throughout the study, and a factor representing reduced plasma glucose and insulin levels in week 1 of intervention only. Plasma ANP levels were significantly higher during week 1 of the vegetarian diet. CONCLUSIONS: A blood pressure lowering effect of a vegetarian diet during normal working activity was shown. Using factors derived from the biochemical variables, results were in keeping with the hypothesis that these effects may be mediated by reduced sympatho-adrenal activity consequent to altered glucose and insulin handling. An early increase in plasma ANP may contribute to the blood pressure reduction.

Ambulatory blood pressure and heart rate responses to vegetarian meals.

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.

A factorial study of salt restriction and a low-fat/high-fibre diet in hypertensive subjects.

OBJECTIVE: To compare the independent and additive effects of sodium restriction and a low-fat, high polyunsaturated: saturated fatty acids (P:S) ratio, high-fibre diet upon blood pressure. DESIGN: A randomized, parallet, double-blind, placebo-controlled (for sodium) 2 x 2 factorial trial. SETTING: Clinical. PARTICIPANTS: Ninety-five hypertensive subjects (mean blood pressure, 137/83 mmHg), mean age 53.5 years, consuming less than 30 ml ethanol/day were selected from community volunteers. Seventy-nine treated and twelve untreated hypertensives completed the trial. INTERVENTION: Subjects followed either a low-sodium, low-fat/high-fibre diet (less than 60 mmol sodium/day; 30% fat energy; P:S ratio = 1; 30-50 g fibre/day) or a low-sodium, normal-fat/normal-fibre diet (less than 60 mmol sodium/day; 40% fat energy; P:S ratio = 0.3; 15 g fibre/day) for 8 weeks. Half of each group received 100 mmol/day NaCl and the remainder received placebo. MAIN OUTCOME MEASURES: Blood pressure and blood lipids. RESULTS: Sodium restriction significantly reduced standing and supine systolic blood pressure, with no effect upon diastolic blood pressure. The low-fat/high-fibre diet had no effect upon blood pressure, but significantly reduced total cholesterol, low-density lipoprotein cholesterol and high-density lipoprotein cholesterol. CONCLUSIONS: Sodium restriction reduced blood pressure and did not raise low-density lipoprotein cholesterol. A low-fat/high-fibre diet did not reduce blood pressure but lowered cholesterol levels. A combination of the two regimes has the greater potential for reducing cardiovascular risk in hypertensives.

A factorial study of fat and fibre changes and sodium restriction on blood pressure of human hypertensive subjects.

1. Diets used to reduce sodium intake often involve changes in fats and fibre which might themselves affect blood pressure and/or lipid metabolism. To evaluate the relative importance of these dietary changes for the management of hypertension we have studied the independent and additive effects of sodium restriction (less than 60 mmol/day) and a low fat (30% energy), high P/S ratio (1.0), high fibre (30-50 g/day) 'cholesterol lowering' diet. 2. Ninety-five hypertensives entered a four group parallel study with a factorial design. Following 5 weeks familiarization subjects [BP range 109/66-168/105 mmHg] were randomly assigned to either a 'low sodium, cholesterol lowering' diet or a 'low sodium, cholesterol maintaining' diet. Half the subjects in each group were then assigned to 100 mmol/day NaCl supplement and the remainder to placebo. These diets were continued for 8 weeks. Seventy-nine of the 91 hypertensives who completed the study were on antihypertensive therapy throughout. 3. Mean urinary sodium excretion decreased from 137 (54 mmol/day (n = 43) at baseline (B) to 52 (32) mmol/day (n = 45, P = 0.0001) during intervention (I) in the low sodium groups and remained unchanged in the groups which received slow sodium (B = 129 [46], n = 43; I = 134 [29], n = 42). Diet record and plasma fatty acid analysis confirmed that the dietary aims of the study were achieved. 4. Sodium restriction reduced supine and standing systolic BP by a mean (+/- s.e.m.) of 6 +/- 2 and 6 +/- 4 mmHg, respectively (P less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)