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Glycine and Tryptophan Reduce Serum Uric Acid

4/30/2019 2:16:57 PM
glycineAs a central characteristic of gout, hyperuricemia is defined as a serum uric acid concentration higher than 7.0 mg/dL. Hyperuricemia occurs as a result of an imbalance between uric acid synthesis and excretion but is thought to mostly be influenced by decreased renal excretion.

Earlier studies showed glycine reduces uric acid levels

In previous animal studies and preliminary human trials, the amino acid glycine was found to increase urinary excretion of uric acid. Researchers then explored the influence of additional amino acids to synergize with glycine and found that small amounts of tryptophan enhanced glycine’s uric acid-lowering effect.

More recent studies examine glycine and tryptophan mix for uric acid reduction

In a study published in Nutrients in 2019, researchers evaluated the effects of combined supplementation with glycine and tryptophan on serum uric acid levels. Thirty-two healthy, Japanese adults (aged 20-64) with mild hyperuricemia participated in this randomized, double-blind, placebo-controlled, crossover trial. Participants took the amino acid mixture or a placebo for 6 weeks and then crossed over to the other arm after a 4-week washout period. Serum uric acid levels and other parameters were measured at baseline and the end of each 6-week intervention period.
The amino acid mixture provided a daily dosage of 3.0 grams of glycine (obtained from Yuki Gosei Kogyo Co., Ltd., Tokyo, Japan) and 0.2 grams of l-tryptophan (obtained from Ajinomoto Healthy Supply, Inc., Tokyo, Japan). The amino acid powder or placebo powder were taken once daily at bedtime. 

Results show synergy of glycine and tryptophan for uric acid reduction

Results showed that the glycine-tryptophan combination significantly lowered serum uric acid levels from baseline to 6-weeks (from 7.1 mg/dL to 6.7 mg/dL; p=.004). The amino acid combination also significantly lowered serum uric acid concentrations in comparison with placebo (-0.4 mg/dL vs. -0.1 mg/dL; p=.028). Additional analyses found that the glycine-tryptophan combination significantly lowered serum triglycerides (from 119 mg/dL to 86 mg/dL; p=.002).
The precise mechanisms by which glycine and tryptophan synergize to reduce serum uric acid levels is not known. The authors of this study proposed that the amino acids may have increased urinary pH and thus increased the solubility of urinary uric acid and increased urate clearance.
This study provided preliminary evidence that supplementation with 3.0 grams of glycine and 0.2 grams of tryptophan per day for 6 weeks significantly decreased serum uric acid levels in subjects with mild hyperuricemia. Clinical trials with larger sample sizes and for longer intervention periods are needed to confirm these effects.
Oshima S, Shiiya S, Nakamura Y. Serum Uric Acid-Lowering Effects of Combined Glycine and Tryptophan Treatments in Subjects with Mild Hyperuricemia: A Randomized, Double-Blind, Placebo-Controlled, Crossover Study. Nutrients. 2019; 11.

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