Science Update

Meta-Analysis and Systematic Review Suggests Supplemental L-Arginine may Help Reduce Waist Circumference

L-arginine is a conditionally essential amino acid that is used for several biological processes within the body. It plays critical roles in cellular division, wound healing, removing ammonia from the body, immune function, and the release of growth hormone. One of L-arginine’s primary functions as a substrate is nitric oxide (NO) synthase, which has been shown to significantly reduce blood pressure. It not only supports NO production, but it has been shown to improve glucose metabolism, lower blood sugar, and positively affect renal function, demonstrating its beneficial effects on metabolic parameters.  

A recent systematic review and meta-analysis of randomized clinical trials, published in the International Journal for Vitamin and Nutrition Research, investigated the efficacy of supplemental L-arginine on obesity-related indices, including weight, waist circumference, and body mass index (BMI). Results from previous clinical studies have been inconsistent regarding the effects of L-arginine on human anthropometrics. After inclusion and exclusion criteria were established, eight studies (published between 2001 and 2017) were eligible and included 222 participants in nine different treatment arms and 239 controls across all studies. Qualified studies included obese or type 2 diabetic participants ages 18 to 75 years. Dosages ranged from 2 to 9 grams per day among the studies conducted from 3 weeks up to 25 weeks. 

Findings from the current study showed that L-arginine supplementation most significantly reduced waist circumference (P = 0.001) compared to a placebo. Subgroup analysis results from only three studies reported L-arginine supplementation significantly reduced body weight when taken for 8 weeks or longer compared to a placebo. Only two studies showed a significant reduction in BMI; however, subgroup analyses demonstrated that longer term interventions of 8 weeks or longer using <8 g per day may significantly decrease BMI. 

Obesity — defined as a BMI ≥30 — is now recognized as a global epidemic, with more than 600 million adults classified as obese worldwide. Nearly half of all adults in the U.S. will be obese by 2030. Waist circumference is a more accurate measurement and predictor of general health than BMI. Evidence shows that a high waist circumference increases the risk of developing several conditions, including hypertension, diabetes, high cholesterol, joint pain, low back pain, and hyperuricemia

Obesity parameters that do not respond to basic lifestyle changes can be rooted in various etiological dysfunctions that may require dietary supplemental support, including dietary modifications, exercise, less toxin exposure, and stress and sleep management. Other than L-arginine, there are many other nutraceuticals that may help improve anthropometrics. Oxidative stress and inflammation are nearly always both a cause and effect of obesity, making antioxidant support a necessary addition to any treatment plan. Epigallocatechin gallate (EGCG) from green tea extract, 7-oxo dehydroepiandrosterone (DHEA), and Garcinia cambogia may help maintain and improve lean body mass and support basal metabolic rate. Prebiotics and probiotics combined — also known as synbiotics — have additionally demonstrated beneficial effects on weight loss and metabolic syndrome, and oral glutamine was shown to reduce waist circumference. Even though dietary supplements may be efficacious in supporting weight loss, implementing healthy dietary intake and regular exercise habits are fundamental to achieving and maintaining a healthy weight.

By Caitlin Higgins, MS, CNS, LDN