Effect of Monosodium Glutamate on Microbiome-Derived Imidazole Propionate Production in Healthy Volunteers

Conditions

• Healthy Adult

Eligibility Criteria

Sex

ALL

Age

18 Years - N/A

Healthy Volunteers

Accepted

Interventions

• L-histidine — DIETARY_SUPPLEMENT
  USP-grade L-histidine, 4 g/day, taken as capsules divided into 2 g in the morning and 2 g in the evening with meals, during each 7-day treatment period. Administered in both treatment periods for all participants.
• Monosodium glutamate (MSG) — DIETARY_SUPPLEMENT
  Food-grade monosodium glutamate, 3 g/day, provided as identical-appearing single-dose powder sachets divided into 1.5 g in the morning and 1.5 g in the evening, each dissolved in approximately 240 mL
• Sodium chloride (NaCl) — DIETARY_SUPPLEMENT
  USP-grade sodium chloride, 940 mg/day, provided as identical-appearing single-dose powder sachets divided into 470 mg in the morning and 470 mg in the evening, each dissolved in approximately 240 mL of water and taken with meals during the placebo treatment period. The sodium content is matched to that of the 3 g/day MSG dose to isolate the effect of glutamate.

Study Details

The goal of this clinical trial is to learn whether dietary monosodium glutamate (MSG), a common food flavor enhancer, increases the blood level of a gut-microbiome-derived compound called imidazole propionate (ImP) in healthy adult volunteers. ImP is a compound made by gut bacteria from the amino acid histidine, and higher blood levels have been linked to problems with blood-sugar control. The main questions this trial aims to answer are: Does taking MSG together with L-histidine increase blood ImP levels compared with taking a salt (sodium chloride) placebo together with L-histidine? How do blood ImP levels change over time in response to MSG and L-histidine taken together? Researchers will compare a 7-day period of L-histidine plus MSG against a 7-day period of L-histidine plus sodium chloride (a salt placebo with matching sodium content) to see whether MSG changes blood ImP levels. Each participant completes both periods in random order and serves as their own comparison. Participants will: Take L-histidine capsules twice daily (morning and evening with meals) during two separate 7-day periods. Dissolve either MSG powder or salt powder in water and drink it twice daily during each period, with the two periods separated by a 7-day break (washout). Give a fasting blood sample at the start of the study and on day 7 of each period. Optionally provide a stool sample at the end of each period. Complete a daily treatment diary and a follow-up phone call after the final sample.

Key Dates

First listed

Jul 14, 2026

Start date

Jul 15, 2026

Status verified

Jul 2026

Primary completion

Dec 31, 2027

Completion

Dec 31, 2027

Study Design

Enrollment

18 participants (estimated)

Allocation

RANDOMIZED

Intervention model

CROSSOVER

Primary purpose

BASIC_SCIENCE

Arms

• Experimental: Sequence 1: L-histidine + MSG, then L-histidine + NaCl
  Participants receive L-histidine (4 g/day) plus monosodium glutamate (MSG; 3 g/day) during the first 7-day treatment period, followed by a 7-day washout, then L-histidine (4 g/day) plus sodium chloride (NaCl; 940 mg/day) during the second 7-day treatment period. L-histidine is taken as capsules (2 g morning, 2 g evening with meals); MSG and NaCl are dissolved in approximately 240 mL of water and taken twice daily (morning and evening with meals).
• Experimental: Sequence 2: L-histidine + NaCl, then L-histidine + MSG
  Participants receive L-histidine (4 g/day) plus sodium chloride (NaCl; 940 mg/day) during the first 7-day treatment period, followed by a 7-day washout, then L-histidine (4 g/day) plus monosodium glutamate (MSG; 3 g/day) during the second 7-day treatment period. L-histidine is taken as capsules (2 g morning, 2 g evening with meals); MSG and NaCl are dissolved in approximately 240 mL of water and taken twice daily (morning and evening with meals).

Primary Outcome Measure

Difference in blood imidazole propionate concentration between the monosodium glutamate and sodium chloride treatment periods [ Time Frame: Day 7 of each treatment period ]

Central Contacts

• Sam Light, PhD
  773-702-3435
  [email protected]

Locations (1)

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