Effect of Vegetarien Diet on Protein Digestibility in Young and Elderly Volunteers
Effect of a Vegetarian Diet on the Bioavailability of Amino Acids From Plant Protein in Healthy Young and Elderly Volunteers (VEGAA)
Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement
48 participants
Oct 22, 2025
INTERVENTIONAL
Conditions
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.
Eligibility
Inclusion Criteria7
- 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
Exclusion Criteria15
- 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.
- 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
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Interventions
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.
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.
Locations(1)
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NCT07521189