The Durk Pearson & Sandy Shaw®
Life Extension NewsTM
Volume 12 No.
1 • Feb. 2009
Short-Term Oral L-Arginine Improves Fasting Vascular Endothelial Function
A recent meta-analysis of 12 randomized controlled trials for short term L-arginine oral supplementation reported an improvement in flow-mediated dilation (FMD, the ability of blood vessels to relax in response to appropriate stimuli, such as acetylcholine release), but only when baseline FMD is low. Note the similarity to the result with Vitamin C and CRP where CRP was reduced only when baseline CRP was high.* In this instance, L-arginine supplementation significantly increased FMD when the baseline levels were <7%, but had no effect when baseline FMD was >7%. In the pooled analysis (in which all subjects were included), L-arginine supplementation significantly increased the FMD by 1.98%, whereas the FMD was increased by 2.56% in those with baseline FMD <7% and was not significantly changed (–0.27%) in those whose baseline FMD was >7%. In order to understand the effects of L-arginine on FMD as reported in these trials, it is necessary to know the baseline levels of FMD and to analyze the effects on the basis of changes in baseline FMD. The trials included in the meta-analysis had 10 to 36 subjects, doses of L-arginine ranged from 3 g to 24 g per day, and subjects included children with chronic kidney failure, patients with heart failure, healthy young men, healthy individuals older than 70 y, clinically asymptomatic elderly subjects, patients with peripheral artery disease, or hypercholesterolemic patients. L-arginine was taken 3 times/d in most studies, with duration of treatment from 3 days to 6 months.
We both take L-arginine supplements (our InnerPower Plus™ formulation contains 6 grams of L-arginine per serving). Though neither of us has to our knowledge a low baseline FMD, there are many other healthful properties of L-arginine (which we have written about in earlier newsletters), such as its action as a precursor of nitric oxide, important for numerous functions, including proper endothelial vasodilation. As another example, arginine supports healthy kidney function by reducing the age-associated increase in the basement membrane (thickening of which reduces the kidney’s ability to filter blood) as well as being part of the urea cycle that allows the body to excrete ammonia formed during the metabolism of amino acids.
- Bai et al. Increase in fasting vascular endothelial function after short-term oral L-arginine is effective when baseline flow-mediated dilation is low: a meta-analysis of randomized controlled trials. Am J Clin Nutr 89:77-84 (2009).