Effect of Vegetarien Diet on Protein Digestibility in Young and Elderly Volunteers

NCT07521189 | Recruiting

• 1 other identifier: VEGAA
• Study Type: interventional
• Target: 48
• Locations: 1 country
• Sites: 1

Brief Summary

Plant proteins are usually less digestible than animal proteins, but they may benefit gut health through effects on the microbiome. The long-term impact of diets rich in plant products on protein digestion and metabolism is still unknown, especially in older adults with higher protein needs. This study aims to compare the digestion and use of pea proteins in young and older adults, both vegetarians and omnivores. Volunteers are divided into four groups: young omnivores, young vegetarians, older omnivores, and older vegetarians. They take part in two clinical investigation days. On the first day, nitrogen retention and protein metabolism is measured after consumption of a pea-based meal. On the second day, amino acid digestibility of pea is evaluated. These results will provide valuable data on how plant proteins are digested and metabolized depending on age and diet. They will also help determine whether aging reduces the availability of plant proteins. This knowledge is important to support nutritional strategies for populations with specific protein needs, such as older adults.

Conditions

Vegetarian Diet; Elderly; Young Healthy Adults

Keywords

Amino acid bioavailability; Vegetarian diet; Elderly; Plant protein; Protein utilization; Isotopic method

Outcome Measures

Primary Outcomes (1)

• Pea amino acid bioavailability (%)

  During the second inverstigation day, the feeding protocol in portions of the meal (pea protein labelled with 2H and dose of 13C-free amino acids) will make it possible to obtain a plateau of isotopic enrichment in 2H and 13C in plasma amino acid. The ratio of 2H isotopic enrichment to 13C isotopic enrichment for each amino acid in the meal and in plasma, corrected by the digestibility of the reference protein (13C-labeled free amino acid mixture with a theoretical digestibility of 100%), makes it possible to determine the bioavailability (also called digestibility) of amino acids from pea protein in the different groups and expressed as % pea amino acids.

  From the begining of the second investigation day (8:00) to 8 hours after the first meal intake (around 18:00).

Secondary Outcomes (2)

• Postprandial desamination of pea protein (%)

  From the begining of the first investigation day (8:00) to 8 hours after the first meal intake (around 18:00).

• Plasma kinetics of pea protein (%)

  From the begining of the first investigation day (8:00) to 8 hours after the first meal intake (around 18:00).

Other Outcomes (2)

• Oxydation of 13C amino acid (%)

  From the begining of the second investigation day (8:00) to 8 hours after the first meal intake (around 18:00).

• Plasma kinetics of intestinal and metabolic hormones (pmol/L)

  From the begining of the first investigation day (8:00) to 8 hours after the first meal intake (around 18:00).

Study Arms (4)

Young adult, vegetarian

EXPERIMENTAL

Young adult (18-23 years) with a vegetarian diet: exclusion of meat and fish/seafood, with \> 70% of protein intake from plant source

Biological: Postprandial test; Biological: Amino acid bioavailability

Young, omnivore

EXPERIMENTAL

Young adult with omnivorous: regular consumption of meat products, with meat intake \> 3 times/week and \> 70% of protein intake from animal sources

Biological: Postprandial test; Biological: Amino acid bioavailability

Old adult, vegetarian

EXPERIMENTAL

Old adult (65-75 years) with vegetarian diet: exclusion of meat and fish/seafood, with \> 70% of protein intake from plant sources

Biological: Postprandial test; Biological: Amino acid bioavailability

Old adult, omnivorous

EXPERIMENTAL

Old adult (65-75 years) with omnivorous diet: regular consumption of meat products, with meat intake \> 3 times/week and \> 70% of protein intake from animal sources

Biological: Postprandial test; Biological: Amino acid bioavailability

Interventions

Postprandial test BIOLOGICAL

A meal containing pea protein labelled with 15N will be eaten by volunteers and dietary nitrogen kinetics will be measured in plasma urea, free amino acids and protein as well as in urinary urea.

Old adult, omnivorous; Old adult, vegetarian; Young adult, vegetarian; Young, omnivore

Amino acid bioavailability BIOLOGICAL

A meal containing pea protein labelled with 2H will be given in a small portions every 30 minutes together with a dose of 13C-labelled amino acid and bioavailability of pea amino acid will be determined with the dual isotopic tracer method.

Old adult, omnivorous; Old adult, vegetarian; Young adult, vegetarian; Young, omnivore

Eligibility Criteria

• Age: 18 Years - 75 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Normal weight or overweight (18 \< BMI \< 30 kg·m-²)
• Male or female
• Aged 18-23 years (young groups) or 65-75 years (older groups)
• In good general health (WHO = 0)
• Affiliated with a social security system
• Free and informed consent, provided in writing after receiving the information required by the Public Health Code

You may not qualify if:

• Adults under legal protection or unable to give informed consent (e.g., under guardianship, trusteeship, or legal protection)
• Any known food allergy
• Positive serology for HBsAg, anti-HBc, HCV, or HIV
• Anemia: hemoglobin level \< 13 g/dL in men and \< 12 g/dL in women
• Diabetes: type 1 or type 2 diabetes, or fasting blood glucose \> 1.25 g/L.
• Gastrointestinal disease: clinically significant gastrointestinal disorders (bleeding, vomiting, constipation/diarrhea grade \> 1) as judged by the investigator, any inflammatory bowel disease, or acute gastroenteritis in the month prior to the intervention.
• Liver disease: any significant hepatic disorder according to the investigator, or ASAT/ALAT \> 2.5 times the upper normal limit.
• High-level athletes (\> 8 hours of training per week)
• Blood donation within 8 weeks prior to study start
• Absence of free, informed, written consent after receiving the information required by the Public Health Code
• Not affiliated with a social security system

Sponsors & Collaborators

• Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement: lead

Study Sites (1)

Centre de Recherche sur Volontaire, Hopital Avicenne (AP-HP)

Bobigny, France

RECRUITING

Central Study Contacts

Juliane Calvez, PhD

CONTACT

+33189100875; juliane.calvez@agroparistech.fr

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: NON RANDOMIZED
• Masking: NONE
• Purpose: BASIC SCIENCE
• Intervention Model: SEQUENTIAL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Professor

Study Record Dates

• First Submitted: September 23, 2025
• First Posted: April 9, 2026
• Study Start: October 22, 2025
• Primary Completion (Estimated): December 31, 2026
• Study Completion (Estimated): December 31, 2026
• Last Updated: April 9, 2026

Record last verified: 2026-04

Data Sharing

• IPD Sharing: Will not share

Locations

FR (1)