John W Apolzan, Jesse A Stein, Jennifer C Rood, Robbie A Beyl, Shengping Yang, Frank L Greenway, Harris R Lieberman
Journal: Nutrition (Burbank, Los Angeles County, Calif.) 2022;101():111658
PMID: 35691183
Arginine is an amino acid that has many functions within the body including the stimulation of hormones involved in the building of muscle mass and as a precursor for a molecule which stimulates blood vessel dilation. Although it can be produced within the body, during times of stress and at certain life stages additional arginine may be required to aid body processes and supplementation may be of benefit to health. This randomised control trial of 29 individuals aimed to determine the effect of 10g arginine supplementation on growth hormone (GH), which is involved in the promotion of muscle building, and factors involved in heart health in younger healthy men. The results showed that arginine supplementation had limited effects on GH but did increase it at certain time points. Blood sugar levels and a hormone involved in metabolism were also increased, but supplementation did not affect sleep or mood. Arginine supplementation mostly did not affect appetite, but did decrease the desire to eat, and the desire to eat fatty and sweet foods. Metabolites from the gut microbiome were also increased. It was concluded that arginine had limited effect on the hormones measured, but did increase GH, which may be because of metabolites from the gut microbiome. This study could be used by healthcare professionals to understand that arginine supplementation may be of benefit to those with lower muscle mass and poor metabolic health, however recommendations would need more robust evidence.
OBJECTIVES
Arginine is an amino-acid supplement and precursor for nitric-oxide synthesis, which affects various biologic processes. The objective of this study was to determine the effects of arginine supplementation on growth hormone (GH) and metabolic parameters.
METHODS
Thirty physically active, healthy men (age 18-39 y; body mass index: 18.5-25 kg/m) were randomized in a double-blind, placebo-controlled, crossover trial. Arginine (10 g) and placebo (0 g) beverages were consumed after an overnight fast. Blood samples were collected at baseline and 1.5, 3.0, and 24 h after supplementation. The primary outcomes were serum GH and metabolomics. Also, amino acids, glucose, insulin, triacylglycerols, thyroid hormones, testosterone, cortisol, dehydroepiandrosterone, and mood state were assessed. Individuals with detectable increases in GH were analyzed separately (responders: n = 16; < 0.05 ng/mL at 1.5 h). Repeated-measure analyses of variance estimated the treatment effects at each timepoint.
RESULTS
Arginine levels increased at 1.5 h (146%) and 3.0 h (95%; P ≤ 0.001) and GH (193%) and thyroid-stimulating hormone (TSH; 10%) levels at 24 h (P < 0.05) after arginine versus placebo consumption. Arginine versus placebo increased glucose levels at 1.5 h (5%) and 3.0 h (3%; P ≤ 0.001). Arginine versus placebo did not affect other dependent measures, including mood state (P > 0.05), but changes in the urea, glutamate, and citric-acid pathways were observed. Among responders, arginine versus placebo increased GH at 1.5 h (37%), glucose at 1.5 h (4%) and 3.0 h (4%), and TSH at 24 h (9%; P < 0.05). Responders had higher levels of benzoate metabolites at baseline and 1.5 h, and an unknown compound (X-16124) at baseline, 1.5 h, and 24 h that corresponds to a class of gut microbes (P < 0.05).
CONCLUSIONS
Arginine supplementation modestly increased GH, glucose, and TSH levels in younger men. Responders had higher benzoate metabolites and an unknown analyte attributed to the gut microbiome. Future studies should examine whether the increased prevalence of these gut microorganisms corresponds with GH response after arginine supplementation.
Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.
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