Effects of oral supplementation of l-arginine to lower blood pressure

Abstract

Dietary L-arginine supplementation has been proposed to reverse endothelial dysfunction in such diverse pathophysiologic conditions as hypercholesterolemia, coronary heart disease, and some forms of animal hypertension. In particular, chronic oral administration of L-arginine prevented the blood pressure rise induced by sodium chloride loading in salt-sensitive rats. To investigate the effects of L-arginine -rich diets on blood pressure and metabolic and coagulation parameters we performed a single-blind, controlled, crossover dietary intervention in six healthy volunteers. The subjects (aged 39 ± 4 years, body mass index [BMI] 26 ± 1 kg/m2, mean ± SEM) received, in random sequence, three different isocaloric diets, each for a period of 1 week (Diet 1: control; Diet 2: L-arginine enriched by natural foods; Diet 3: identical to Diet 1 plus oral L-arginine supplement). Sodium intake was set at a constant level (about 180 mmol/day) throughout the three study periods. A blood pressure decrease was observed with both L-arginine -rich diets (Diet 2 v 1, SBP: -6.2 mm Hg [95% CI: -0.5 to -11.8], DBP: -5.0 mm Hg [-2.8 to -7.2]; Diet 3 v 1, SBP: -6.2 mm Hg [-1.8 to -10.5], DBP: -6.8 mm Hg [-3.0 to -10.6]). A slight increase in creatinine clearance (P = .07) and a fall in fasting blood glucose (P = .008) occurred after Diet 3 and, to a lesser extent, after Diet 2. Serum total cholesterol (P = .06) and triglyceride (P = .009) decreased and HDL cholesterol increased (P = .04) after Diet 2, but not after Diet 3.

These results indicate that a moderate increase in L-arginine significantly lowered blood pressure and affected renal function and carbohydrate metabolism in healthy volunteers.

Effects of oral supplementation of l-arginine to lower blood pressure

Introduction

Although a few studies have investigated the relationship between dietary protein intake and blood pressure,[1] little interest has been paid thus far to the effect of single amino acids. Recently, the identification of nitric oxide (NO) as a product of the metabolism of L-arginine through the NO synthase pathway[2] has opened a new avenue of research. l-arginine, a so-called “conditionally” essential amino acid largely present in several food items, plays a central role in a number of major metabolic pathways (3). Its average dietary intake is 5.4 grams/day, assuming a total daily protein intake of 100 grams/day (3).

On clinical grounds, interest in the role of this aminoacid has been stimulated by the observation that L-arginine supplementation was able to attenuate the endothelial dysfunction associated with hypercholesterolemia (4) and coronary heart disease (5). Moreover, hypertension induced by sodium chloride loading in Dahl salt-sensitive rats was prevented by chronic dietary L-arginine supplementation.[6, 7 and 8] Yet in other studies the parenteral administration of large doses of L-arginine acutely lowered blood pressure in normotensive[9 and 11] and in salt-sensitive hypertensive individuals. [9, 10 and 11] Against this background, the present study was designed to investigate the effects of increased L-arginine dietary intake—in the form of naturally arginine-rich foods or as a pharmacologic ...