We determined the serum uric acid-lowering effects of combined daily supplementation of glycine and tryptophan in patients with mild hyperuricemia using a randomized, double-blind, placebo-controlled, crossover clinical trial design. Japanese healthy adult males and females with mild hyperuricemia (fasting serum uric acid of 6.6–7.9 mg/dL) 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 6 weeks. Combined supplementation with glycine and tryptophan significantly decreased serum uric acid levels (from 7.1 mg/dL to 6.7 mg/dL, p = 0.004) before and after the trial. Serum uric acid concentrations significantly decreased in the subjects supplemented with the amino acid mixture compared with those in placebo-treated subjects (p = 0.028). In addition, the combination treatment with glycine and tryptophan decreased serum triglyceride levels (from 119 mg/dL to 86 mg/dL, p = 0.002). Increased solubility of uric acid caused by urinary pH were likely contributors to the serum uric acid-lowering effects of the amino acid mixture.

The authors previously confirmed the serum uric acid-lowering effects of the combination of glycine and tryptophan in subjects with mild hyperuricemia. This study examined whether combined supplementation with glycine and tryptophan suppressed the elevation in serum uric acid levels caused by purine ingestion and accelerated urinary uric acid excretion in subjects with lower urate excretion using a randomized, single-blind, placebo-controlled, crossover clinical trial design. Healthy Japanese adult males with lower urate excretion ingested water containing purines in addition to dextrin (placebo), tryptophan, glycine, or a glycine and tryptophan mixture. The combined supplementation with glycine and tryptophan significantly reduced the elevated serum uric acid levels after purine ingestion. Glycine alone and in combination with tryptophan significantly increased urinary uric acid excretion and urate clearance compared with the effects of the placebo. Urinary pH increased by the ingestion of the mixture. These results suggested that the improved water solubility of uric acid due to increased urinary pH contributed to the increase of urinary uric acid excretion.

Background: Several studies have analyzed the functions of foods and dietary constituents in the dynamics of alcohol metabolism. However, few studies have reported the function of dietary fibers in the dynamics of alcohol metabolism.Objective: We assessed the effects of botanical foods that contain dietary fibers on alcohol metabolism.Methods: The ability of the water-insoluble fraction (WIF) of 18 kinds of botanical foods to maintain 15% (v/v) ethanol solution was examined using easily handled filtration. A simple linear regression analysis was performed to examine the correlation between the filtered volumes and blood ethanol concentration (BEC) in F344 rats 4 h after the ingestion of 4.0 g/kg of ethanol following dosage of 2.5% (w/v) WIF of the experimental botanical foods. Furthermore, the supernatant (6.3 Brix; water-soluble fraction) and precipitate (WIF of tomato), with a strong ethanol-maintaining ability, were obtained and BEC and the residual gastric ethanol in rats were determined 2 h after the administration of 4.0 g/kg of ethanol and the individuals fractions.Results: The filtered volumes of dropped ethanol solutions containing all the botanical foods tested except green peas were decreased compared with the ethanol solution without WIF (control). There was a significant correlation between the filtered volumes and blood ethanol concentration (BEC). There was no significant difference in the residual gastric ethanol between controls and the supernatant group; however, it was increased significantly in the WIF group than in controls or the supernatant group. Consistent with this, BEC reached a similar level in controls and the supernatant group but significantly decreased in the WIF group compared with controls or the supernatant group.Conclusions: These findings suggest that WIFs of botanical foods, which are mostly water-insoluble dietary fibers, possess the ability to absorb ethanol-containing solutions, and this ability correlates strongly with the inhibition of the blood ethanol response, likely by delaying gastric emptying.Key words: Botanical food, tomato, water-insoluble fraction, dietary fiber, blood ethanol concentration

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.Keywords: glycine, tryptophan, estimated glomerular filtration rate, uric acid

Delay in gastric emptying (GE) lowers the blood ethanol concentration (BEC) after alcohol administration. We previously demonstrated that water-insoluble fractions, mainly comprising dietary fiber derived from many types of botanical foods, possessed the ability to absorb ethanol-containing aqueous solutions. Furthermore, there was a significant correlation between the absorption of ethanol and lowering of BEC because of delay in GE. Here we identified dietary nutrients that synergize with the water-insoluble fraction of tomatoes to lower BEC in rats. Consequently, unlike tomato juice without alanine, tomato juice with 5.0% alanine decreased BEC depending on the delay in GE and mediated the ethanol-induced decrease in the spontaneous motor activity (an indicator of drunkenness). Our findings indicate that the synergism between tomato juice and alanine to reduce the absorption of ethanol was attributable to the effect of alanine on precipitates such as the water-insoluble fraction of tomatoes.