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Completed

NCT Number: NCT07613983

Evaluation of the Bioavailability of Amino Acids From Purple Bacteria

This interventional clinical study aims to evaluate the bioavailability of amino acids derived from purple bacteria in healthy adults. Participants will consume either a protein-enriched dairy product or a protein-enriched dairy product containing purple bacteria during two separate test periods in a randomized cross-over design. Blood amino acid concentrations will be measured over a 4-hour postprandial period to assess amino acid absorption and bioavailability.

Additional biological samples including saliva, exhaled air, and feces will be collected to evaluate gastrointestinal hormones, volatilome profiles, and related metabolic responses.

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Key information

Conditions

Healthy Volunteers

Age range

18 year–50 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Center of Investigation in Clinical Nutrition (CICN)

Louvain-la-Neuve, 1348, Belgium

About this study

Purple bacteria are recognized for their high-quality protein content, including essential amino acids, as well as their vitamin and carotenoid composition. However, limited data are available regarding the bioavailability of amino acids derived from purple bacteria in humans.

This randomized, open-label, cross-over study will enroll approximately 12 healthy adult participants in Belgium. Each participant will receive two dairy-based formulations in randomized order:

Control formulation: protein-enriched dairy product. Test formulation: protein-enriched dairy product containing purple bacteria.

The two intervention periods will be separated by a washout period of at least one week.

Participants will undergo one screening visit and two test visits. During each test visit, serial blood samples will be collected over 240 minutes following ingestion of the assigned formulation to determine plasma amino acid concentrations. Additional saliva, exhaled air, and fecal samples will also be collected.

The primary objective is to determine whether amino acids present in purple bacteria are better absorbed than amino acids from other protein sources.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Adults aged 18 to 50 years
  • Body mass index between 18 and 30 kg/m²
  • Healthy participants
  • Non-smokers
  • Women of childbearing potential using effective contraception
  • Able to understand and speak French
  • Willing and able to comply with study procedures

Exclusion criteria

  • Pregnancy or breastfeeding
  • Use of medications or dietary supplements incompatible with study participation
  • Any medical condition considered by the investigator to interfere with study participation or interpretation of results
  • Vegan or vegetarian diets

Treatment and study plan

Purple Bacteria-Enriched Dairy Product

Dietary Supplement

Approximately 50 g of purple bacteria incorporated into approximately 110 g of a protein-enriched dairy product.

Protein-Enriched Dairy Product

Other

160 g of protein-enriched dairy product.

Primary outcomes

  1. Change in postprandial plasma essential amino acid concentrations (µmol/L)

    Time frame: Throughout the entire study, approxiamtely during 1 month

    Plasma concentrations of essential amino acids (including leucine, isoleucine, valine, lysine, threonine, phenylalanine, methionine, tryptophan, and histidine) will be measured using LC-MS/MS at baseline and at multiple postprandial time points following ingestion of control and test formulations. Results will be reported as incremental area under the curve (iAUC, µmol/L·h) over the postprandial period.

Secondary outcomes

  1. Change in exhaled volatile organic compounds (VOCs) profile (relative abundance, arbitrary units)

    Time frame: Throughout the entire study, approxiamtely during 1 month

    Exhaled air samples will be analyzed using gas chromatography-mass spectrometry (GC-MS). Specific VOCs will be quantified and reported as relative abundance (arbitrary units) and/or multivariate profile changes (e.g., PCA scores) comparing test vs control formulations.

  2. Change in salivary gastrointestinal hormone concentrations (pg/mL)

    Time frame: Throughout the entire study, approxiamtely during 1 month

    Salivary concentrations of gastrointestinal hormones (e.g., ghrelin, GLP-1, PYY) will be measured using immunoassays. Results will be expressed as change from baseline and iAUC (pg/mL·h) over the postprandial period.

  3. Gastrointestinal symptom severity score assessed using a 5-point Likert scale (0-4)

    Time frame: Throughout the entire study, approxiamtely during 1 month

    Gastrointestinal tolerance will be assessed using a standardized symptom questionnaire evaluating the severity of gastrointestinal symptoms (including bloating, abdominal pain, flatulence, nausea, and diarrhea).

    Each symptom will be rated using a 5-point Likert scale, defined as:

    0 = not at all

    • = slightly
    • = moderately
    • = severely
    • = very severely

    Results will be reported as:

    mean gastrointestinal symptom score (average across symptoms) and/or total symptom score (sum of all items; higher scores indicate worse symptoms) and change from baseline over the postprandial period following ingestion of study formulations.

  4. Number of participants with at least one adverse event

    Time frame: Throughout the entire study, approxiamtely during 1 month

    Adverse events will be collected throughout the study period and reported as the number and proportion of participants experiencing at least one adverse event, by condition.

Other outcomes

  1. Perceived stress score assessed using the Perceived Stress Scale (PSS-10; range 0-40)

    Time frame: Throughout the entire study, approxiamtely during 1 month

    Perceived stress will be assessed using the Perceived Stress Scale (10-item version, PSS-10), a validated questionnaire measuring the degree to which situations in one's life are appraised as stressful.

    The total score ranges from:

    0 to 40, with higher scores indicating higher perceived stress

    Results will be reported as:

    mean total PSS score change from baseline over the study period and/or between-group differences following ingestion of the study formulations.

Sponsors and collaborators

Lead sponsor

Université Catholique de Louvain

Other

Collaborators

  • University of Liege
  • University of Mons

Registry information

Official study title

Evaluation of the Consumption of Fresh Purple Bacteria Biomass in Healthy Humans: Safety Test and Monitoring of Metabolism

Acronym: PROTEBOOST_1

Important dates

Study start
2026
Primary completion
2026
Study completion
2026
First posted
May 29, 2026
Registry last updated
May 29, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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