BIOCHEMICAL AND NEUROHORMONAL RESPONSES TO THE INTRODUCTION OF A LACTO-OVOVEGETARIAN DIET

Objective: To assess the mechanisms of the blood pressure-lowering eff ect of a vegetarian diet in the early and later stages of dietary inte rvention. Design: After 2 weeks without intervention (baseline), 20 no rmotensive men were matched for age and body mass index and randomly a llocated 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 we ek of intervention, twice in the second week and weekly thereafter. Bl ood samples collected after a standard breakfast were analysed for pla sma noradrenaline, adrenaline, atrial natriuretic peptide (ANP), renin , aldosterone, glucose and insulin. Factor and multiple regression ana lyses 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 pressu res at work were lower on the vegetarian diet than in the controls. Th is blood pressure decrease was associated with a factor representing l ower plasma catecholamine and renin activity levels throughout the stu dy, and a factor representing reduced plasma glucose and insulin level s in week 1 of intervention only. Plasma ANP levels were significantly higher during week 1 of the vegetarian diet. Conclusions: A blood pre ssure lowering effect of a vegetarian diet during normal working activ ity was shown. Using factors derived from the biochemical variables, r esults were in keeping with the hypothesis that these effects may be m ediated by reduced sympatho-adrenal activity consequent to altered glu cose and insulin handling. An early increase in plasma ANP may contrib ute to the blood pressure reduction.