Enhancing effect of glycine and tryptophan mixture on estimated glomerular filtration rate in healthy participants: A randomized, double-blind, placebo-controlled parallel study

Abstract

Background: The mixture of glycine and tryptophan exhibited serum uric acid-lowering effects in our previous clinical trial. Objective: Using a randomized, double-blind, placebo-controlled, and parallel study design, this current study aimed to examine whether this mixture enhanced the estimated glomerular filtration rate (eGFR) as an indicator of renal function in healthy individuals. Methods: Healthy Japanese adult males and females ingested a powder mixture containing 3.0 g of glycine and 0.2 g of tryptophan or a placebo powder once daily at bedtime for 8 weeks. Results: After 8 weeks of continual ingestion, the combined glycine and tryptophan supplementation significantly enhanced eGFR. It also decreased serum uric acid levels, consistent with our previous reports. Meanwhile, the continual ingestion of the mixture had no influence on serum total or essential amino acids. Conclusions: The current study demonstrated that the combined oral administration of glycine and tryptophan significantly elevated the eGFR of healthy participants. However, further investigation is required to elucidate the detailed mechanisms underlying the potential therapeutic or preventive effect of combined glycine and tryptophan supplementation. Nevertheless, the uric acid-lowering effect of glycine and tryptophan mixture has the potential to directly influence renal function.