Vegetarian DietVEGAANCT07521189
Effect of Vegetarien Diet on Protein Digestibility in Young and Elderly Volunteers
A study testing Postprandial test and Amino acid bioavailability in people with Vegetarian Diet and Elderly, run by Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement at 1 site in France.
Trial 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. Read more about this study
- Who is it for?
- Ages 18 to 75 yearsHealthy volunteers can take part
- Conditions the study is for
- Vegetarian Diet, Elderly, Young Healthy Adults
- What is being tested?
- Postprandial test and Amino acid bioavailability
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 48 participants
- Where
- 1 siteFrance
- Study dates
- 22 Oct 2025to 31 Dec 2026
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 75 years
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- 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)
- Following an omnivorous diet (regular consumption of meat products, with meat intake > 3 times/week and > 70% of protein intake from animal sources) or vegetarian diet (exclusion of meat and fish/seafood, with > 70% of protein intake from plant sources)
- 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
Who cannot join
- 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
- Pregnant women or those who may be pregnant (based on a positive urine pregnancy test at inclusion)
- Excessive alcohol consumption (> 2 drinks/day). Harmful alcohol use will be assessed by the investigator at inclusion.
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- Hypertension, diabetes, gastrointestinal, liver or kidney diseases, or severe heart disease. These conditions will be assessed by the investigator based on standard clinical evaluation and participants' self-reports at inclusion.
- Hypertension: significant arterial hypertension according to the investigator, or systolic blood pressure ≥ 140 mmHg and/or diastolic blood pressure ≥ 90 mmHg at inclusion.
- 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
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
France1 site, 1 recruiting
- Recruiting
Centre de Recherche sur Volontaire, Hopital Avicenne (AP-HP)
Bobigny
Juliane Calvez, PhD, +33189100875, juliane.calvez@agroparistech.fr
Suzette Maurinier, +33148957433, suzette.maurinier@aphp.fr
About this study
Official title: Effect of a Vegetarian Diet on the Bioavailability of Amino Acids From Plant Protein in Healthy Young and Elderly Volunteers (VEGAA)
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.
Read the detailed description
Plant proteins generally have lower digestibility than animal proteins but also provide positive effects on the digestive system, particularly on the gut microbiota. However, the long-term effects of consuming a diet rich in plant-based products on protein digestion are still unknown. In the context of the nutritional transition toward more plant-based diets, it is important to comprehensively study the effect of such diets on the bioavailability of plant proteins. This is especially relevant for populations with specific protein needs, such as older adults.
The aim of the study is to compare the digestive and metabolic bioavailability of pea proteins in young and older adults, vegetarians and omnivores.
Peas are labeled with stable isotopes (15N and 2H), which are completely safe for health. Four groups of 8 healthy volunteers (+ 4 possible dropouts) are recruited according to age and dietary habits: young omnivores (18-23 years), older omnivores (65-75 years), young vegetarians, and older vegetarians. The volunteers' diets are characterized using an online food frequency questionnaire.
Each volunteer participates in two clinical investigation days, separated by 4 weeks to 2 months. On the first investigation day, a postprandial test is conducted after ingestion of a pea-based meal (100 g dry weight) labeled with 15N, consumed in normal conditions (as a bolus). Blood samples are taken regularly over 8 hours (156 mL total), and urine is collected every 2 hours. Postprandial kinetics of plasma amino acids concentrations, incorporation of dietary nitrogen in plasma protein and free amino acids as well as plasma gut hormones and protein metabolism markers are determined. Desamination of dietary protein is evaluated through determination of dietary nitrogen in plasma and urinary urea.
On the second investigation day, participants undergo the dual isotope tracer method to assess the digestibility of amino acids from pea proteins. They consume a pea-based meal (100 g dry weight) labeled with 2H, distributed in portions every 30 minutes for 7.5 hours. Free amino acids labeled with 13C are added to each portion. Blood samples are collected regularly over 8 hours (130 mL total). Respiratory exchanges are measured by indirect calorimetry in 15-minute periods every hour, and breath samples are collected regularly. 2H and 13C enrichment in individual amino acids are determined in plasma from 5 to 8h during a plateau. Oxydation of 13C amino acids is evaluated through measurement of 13CO2 in expired air.
The results will provide data on the digestive and metabolic bioavailability of plant proteins and amino acids in young and older individuals, whether vegetarian or omnivore. This study will therefore contribute to advancing knowledge about the digestibility of plant proteins and how it changes with aging, a question for which little data is currently available.
- Conditions
- Vegetarian Diet, Elderly, Young Healthy Adults
- Being tested
- Postprandial test, Amino acid bioavailability
- Keywords
- Amino acid bioavailability, Vegetarian diet, Elderly, Plant protein, Protein utilization, Isotopic method
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Postprandial testBiological
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.
Amino acid bioavailabilityBiological
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.
| Study group | Role | What they receive |
|---|---|---|
| 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 Receives: 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 Receives: 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 Receives: 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 Receives: Biological: Postprandial test; Biological: Amino acid bioavailability |
What is being measured
The primary outcome is the main question the study is designed to answer.
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.
Measured: 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 (%)
During the first day of investigation, the volunteers will eat the meal containing pea protein labelled with 15N and blood and urine samples will be taken. The analyses of 15N enrichment in plasma and urinary urea make it possible to assess the postprandial deamination of the plant protein, reflecting its metabolic bioavailability (expressed as % pea amino acids), in the different groups.
Measured: 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 (%)
During the first day of investigation, the volunteers will eat the meal containing pea protein labelled with 15N. The analyses of isotopic enrichments in the different plasma fractions (protein and free amino acids) make it possible to assess the kinetics of the release of amino acids from the pea protein in the different groups, expressed as % pea amino acids.
Measured: From the begining of the first investigation day (8:00) to 8 hours after the first meal intake (around 18:00).
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted9 Apr 2026
- Study start22 Oct 2025
- Primary completion31 Dec 2026 (estimated)
- Study completion31 Dec 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Vegetarian DietStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Basic science
- Allocation
- Non-randomised
- Intervention model
- Sequential
- Masking
- None (open label)
- Enrolment
- 48 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Robert Benamouzig, Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07521189
- Sponsor's protocol ID
- VEGAA
- Acronym
- VEGAA
- Status last verified
- Apr 2026
- First submitted
- 23 Sep 2025
- Last updated
- 9 Apr 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 9 Apr 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Effect of a Vegetarian Diet on the Bioavailability of Amino Acids From Plant Protein in Healthy Young and Elderly Volunteers (VEGAA)
- ClinicalTrials.gov ID
- NCT07521189
- Acronym / sponsor ID
- VEGAA / VEGAA
- Conditions
- Vegetarian Diet, Elderly, Young Healthy Adults
- Keywords
- Amino acid bioavailability, Vegetarian diet, Elderly, Plant protein, Protein utilization, Isotopic method
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 48 participants (estimated)
- Lead sponsor
- Institut National de Recherche pour l'Agriculture, l'Alimentation et l'EnvironnementUniversity, hospital or other
- Study start
- 22 Oct 2025 (actual)
- Primary completion
- 31 Dec 2026 (estimated)
- Study completion
- 31 Dec 2026 (estimated)
- First posted
- 9 Apr 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Detailed description
Plant proteins generally have lower digestibility than animal proteins but also provide positive effects on the digestive system, particularly on the gut microbiota. However, the long-term effects of consuming a diet rich in plant-based products on protein digestion are still unknown. In the context of the nutritional transition toward more plant-based diets, it is important to comprehensively study the effect of such diets on the bioavailability of plant proteins. This is especially relevant for populations with specific protein needs, such as older adults.
The aim of the study is to compare the digestive and metabolic bioavailability of pea proteins in young and older adults, vegetarians and omnivores.
Peas are labeled with stable isotopes (15N and 2H), which are completely safe for health. Four groups of 8 healthy volunteers (+ 4 possible dropouts) are recruited according to age and dietary habits: young omnivores (18-23 years), older omnivores (65-75 years), young vegetarians, and older vegetarians. The volunteers' diets are characterized using an online food frequency questionnaire.
Each volunteer participates in two clinical investigation days, separated by 4 weeks to 2 months. On the first investigation day, a postprandial test is conducted after ingestion of a pea-based meal (100 g dry weight) labeled with 15N, consumed in normal conditions (as a bolus). Blood samples are taken regularly over 8 hours (156 mL total), and urine is collected every 2 hours. Postprandial kinetics of plasma amino acids concentrations, incorporation of dietary nitrogen in plasma protein and free amino acids as well as plasma gut hormones and protein metabolism markers are determined. Desamination of dietary protein is evaluated through determination of dietary nitrogen in plasma and urinary urea.
On the second investigation day, participants undergo the dual isotope tracer method to assess the digestibility of amino acids from pea proteins. They consume a pea-based meal (100 g dry weight) labeled with 2H, distributed in portions every 30 minutes for 7.5 hours. Free amino acids labeled with 13C are added to each portion. Blood samples are collected regularly over 8 hours (130 mL total). Respiratory exchanges are measured by indirect calorimetry in 15-minute periods every hour, and breath samples are collected regularly. 2H and 13C enrichment in individual amino acids are determined in plasma from 5 to 8h during a plateau. Oxydation of 13C amino acids is evaluated through measurement of 13CO2 in expired air.
The results will provide data on the digestive and metabolic bioavailability of plant proteins and amino acids in young and older individuals, whether vegetarian or omnivore. This study will therefore contribute to advancing knowledge about the digestibility of plant proteins and how it changes with aging, a question for which little data is currently available.
Study design
- Primary purpose
- Basic science
- Allocation
- Non-randomised
- Intervention model
- Sequential
- Masking
- None (open label)
- Number of arms
- 4
| Arm | Type | Receives |
|---|---|---|
| Young adult, vegetarian | Experimental | Biological: Postprandial test, Biological: Amino acid bioavailabilityYoung adult (18-23 years) with a vegetarian diet: exclusion of meat and fish/seafood, with > 70% of protein intake from plant source |
| Young, omnivore | Experimental | Biological: Postprandial test, Biological: Amino acid bioavailabilityYoung adult with omnivorous: regular consumption of meat products, with meat intake > 3 times/week and > 70% of protein intake from animal sources |
| Old adult, vegetarian | Experimental | Biological: Postprandial test, Biological: Amino acid bioavailabilityOld adult (65-75 years) with vegetarian diet: exclusion of meat and fish/seafood, with > 70% of protein intake from plant sources |
| Old adult, omnivorous | Experimental | Biological: Postprandial test, Biological: Amino acid bioavailabilityOld 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 |
Who may qualify
- Ages
- 18 to 75 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (7 listed)
- 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)
- Following an omnivorous diet (regular consumption of meat products, with meat intake > 3 times/week and > 70% of protein intake from animal sources) or vegetarian diet (exclusion of meat and fish/seafood, with > 70% of protein intake from plant sources)
- In good general health (WHO = 0)
Key exclusion criteria (15 listed)
- 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
- Pregnant women or those who may be pregnant (based on a positive urine pregnancy test at inclusion)
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Postprandial testA 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. | Biological | Old adult, omnivorous, Old adult, vegetarian, Young adult, vegetarian, Young, omnivore |
| Amino acid bioavailabilityA 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. | Biological | Old adult, omnivorous, Old adult, vegetarian, Young adult, vegetarian, Young, omnivore |
Primary outcome
Pea amino acid bioavailability (%)
Time frame: From the begining of the second investigation day (8:00) to 8 hours after the first meal intake (around 18:00).
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.
2 secondary outcomes
Postprandial desamination of pea protein (%)
Time frame: 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 (%)
Time frame: From the begining of the first investigation day (8:00) to 8 hours after the first meal intake (around 18:00).
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 9 Apr 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Postprandial test and Amino acid bioavailability in people with Vegetarian Diet and Elderly, run by Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement at 1 site in France.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 7 inclusion and 15 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 9 Apr 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in France. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Juliane Calvez, PhD (+33189100875, juliane.calvez@agroparistech.fr), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Pea amino acid bioavailability (%) (time frame: From the begining of the second investigation day (8:00) to 8 hours after the first meal intake (around 18:00).). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 9 Apr 2026.