Effects of Pea Proteins With Different Degrees of Processing on Postprandial Metabolism in Healthy Adults

In a randomized crossover-design, 20 healthy women and men consume 4 test meals containing either 25 g of protein from plant protein ingredients (pea protein concentrate, isolate, or extrudate) or whey protein together with 1 g paracetamol, which is used as a marker for gastric emptying.

During a postprandial period of 6 hours parameters of protein metabolism (e.g. amino acids in plasma and urine), glucose metabolism (plasma glucose, serum insulin) and gastric emptying rate (based on plasma paracetamol) are analysed. Furthermore, subjective hunger/satiety and acceptance of the meals are assed using visual analogue scales. Each intervention arm will be separated by a washout period of at least 7 days.

• Pea protein concentrate (Other): Ingestion of a soup containing 25 g of protein from pea protein concentrate
• Pea protein isolate (Other): Ingestion of a soup containing 25 g of protein from pea protein isolate
• Pea protein extrudate (Other): Ingestion of a soup containing 25 g of protein from pea protein extrudate
• Whey protein (Other): Ingestion of a soup containing 25 g of protein from whey protein

Primary outcomes

• Amino acid profile in blood [Postprandial period of 5 hours (Time points: fasting (0) and 15, 30, 45, 60, 90, 120, 180, 240 and 300 minutes)]: Analysis of amino acid profile in plasma (nmol/ml)

Secondary outcomes

• Parameters of protein metabolism in blood I [Postprandial period of 5 hours (Time points: fasting (0) and 30, 60, 90, 120, 180, 240 and 300 minutes)]: Analysis of urea (mg/dL and mol/L) in blood
• Parameters of protein metabolism in blood II [Postprandial period of 5 hours (Time points: fasting (0) and 60, 120, 180, 240 and 300 minutes)]: Analysis of nitrogen (mg/dL) in blood
• Parameters of glucose metabolism in blood I [Postprandial period of 5 hours (Time points: fasting (0) and 30, 60, 90, 120, 180, 240 and 300 minutes)]: Analysis of glucose (mg/dL and mmol/L) in blood
• Parameters of glucose metabolism in blood II [Postprandial period of 5 hours (Time points: fasting (0) and 30, 60, 90, 120, 180, 240 and 300 minutes)]: Analysis of insulin (nmol/L and pmol/L) in blood
• Gastric emptying rate [Postprandial period of 5 hours (Time points: fasting (0) and 30, 60, 90, 120, 180, 240 and 300 minutes)]: Analysis of gastric emptying rate based on paracetamol kinetics in blood (µg/mL)
• Hunger/satiety and acceptance of the meals [Postprandial period of 5 hours (Time points: fasting (0) and 15, 30, 45, 60, 90, 120, 180, 240 and 300 minutes)]: Assessment of subjective hunger/satiety and acceptance of the meals by validated visual analogue scale questionnaires (e.g., 0 = not hungry at all, 10 = very hungry)
• Uric acid in blood [Postprandial period of 5 hours (Time points: fasting (0) and 30, 60, 90, 120, 180, 240 and 300 minutes)]: Analysis of uric acid (mg/dL and mmol/L) in blood
• Copper in blood [Postprandial period of 5 hours fasting (0) and 60, 120, 180, 240 and 300 minutes)]: Analysis of copper (µg/l) in blood
• Zinc in blood [Postprandial period of 5 hours fasting (0) and 60, 120, 180, 240 and 300 minutes)]: Analysis of zinc (µg/l) in blood
• Iron in blood [Postprandial period of 5 hours fasting (0) and 60, 120, 180, 240 and 300 minutes)]: Analysis of iron (µg/l) in blood
• Selenium in blood [Postprandial period of 5 hours fasting (0) and 60, 120, 180, 240 and 300 minutes)]: Analysis of selenium (µg/l) in blood
• Amino acid profile in urine [Postprandial period of 5 hours]: Analysis of amino acids in urine (nmol/mL)

Sex: All, ages: 20 Years to 40 Years, accepts healthy volunteers

Inclusion Criteria:

* non-smoking
* metabolically healthy
* normal weight (BMI: 18,5 - 24,9 kg/m2)
* written informed consent

Exclusion Criteria:

* pregnancy, lactation
* hypo- or hypertension
* underweight or overweight/obesity
* food intolerances and allergies (especially milk protein, pea, celery)
* malabsorption syndromes
* gastrointestinal diseases
* thyroid diseases
* diabetes mellitus type 1 and type 2
* impaired kidney or liver function
* anaemia
* blood coagulation disorders
* irregular menstrual cycle
* endometriosis, severe menstrual problems
* hormonal contraception
* regular use of medications (especially habitual use of paracetamol or medications that may interact with paracetamol)
* hypersensitivity to paracetamol
* body weight below 50 kg
* alcohol abuse
* glucose-6-phosphate dehydrogenase deficiency
* Gilbert's syndrome
* vegan diet
* eating disorders (especially anorexia nervosa, bulimia nervosa)
* smoking
* participation in another study

• Results publication: Klug L, Diekmann C, Kopp C, Acir IH, Gola S, Opaluwa C, Stoffel-Wagner B, Coenen M, Nemeth R, Daniel H, Schweiggert-Weisz U, Egert S. Delayed Plasma Amino Acid Response following Ingestion of Extruded Pea Protein Compared with Nonextruded Pea Proteins in Healthy Adults: A Randomized Crossover Trial. J Nutr. 2026 Jul 28;156(9):101746. doi: 10.1016/j.tjnut.2026.101746. Online ahead of print. PMID 42520972

• Sarah Egert, Prof PhD, Principal investigator, Germany University of Bonn