Low-grade Inflammation and Gut Symptoms From A2 and Hydrolyzed A1 Milk

Low-grade Inflammation and Gut Symptoms From A2 and Protein-hydrolysed Lactose-free A1 Milk in Lactose-tolerant and Lactose-intolerant Volunteers

The aim of this study is to reveal how different forms of milk casein, lactose and moderate breakdown of proteins affect the symptoms that may arise from milk and markers of inflammation in volunteers receiving symptoms from milk. Research hypotheses are: 1) Protein hydrolyzed milk is as tolerated or better tolerated than A2 milk, and 2) Lactose is the main causative agent of stomach symptoms in milk-sensitive individuals.

Study Overview

• Status: Completed
• Conditions: Milk Intolerance
• Intervention / Treatment: Other: Dietary intervention

• Study Type: Interventional
• Enrollment (Actual): 37
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Finland
  • Turku
    • Turku, Turku, Finland, 20500
      • Food Sciences, Department of Life Technologies, University of Turku

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 65 years (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Perceive disturbing gut symptoms from regular milk
• Commits to the research diet for the whole research period
• Age: 18-65
• BMI: 18.5-30
• Healthy (normal kidney, liver and thyroid function and self-reported)

Exclusion Criteria:

• Milk allergy
• Regular medication (other than contraceptives) or medication affecting the gut
• Recent course of antibiotics (< 3 months prior the study)
• Pregnancy or lactation
• Diagnosed bowel disease

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Quadruple

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: A2 milk + placebo; A2 whole milk, 3.5% fat, heat-treated; placebo capsule without enzyme	Other: Dietary intervention; The arising gastrointestinal symptoms and inflammation markers from consumption of milk + lactase capsule / placebo.
Experimental: A2 milk+ lactase enzyme; A2 whole milk, 3.5% fat, heat-treated; lactase capsule	Other: Dietary intervention; The arising gastrointestinal symptoms and inflammation markers from consumption of milk + lactase capsule / placebo.
Experimental: Protein-hydrolyzed A1 milk + placebo; Protein-hydrolyzed lactose-free milk, 3% fat, heat-treated; placebo capsule without enzyme	Other: Dietary intervention; The arising gastrointestinal symptoms and inflammation markers from consumption of milk + lactase capsule / placebo.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Changes from baseline in Inflammation marker IL-4	IL-4 (interleukin 4) is measured from fasting plasma samples at the baseline before the study and then after each 3-day study arm on the 4th day. It will be analysed as part of the Olink Target 48 Cytokine Panel (Olink Proteomics, Uppsala, Sweden) that provides absolute quantities for 45 different proteins, such as interleukins, interferons, chemokines and growth factors that are related to inflammation. Differences in plasma inflammation marker is measured as a baseline	after treatment (4th day)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Changes from Baseline in Inflammation markers	Inflammation markers of 45 different proteins, such as interleukins, interferons, chemokines and growth factors are measured from fasting plasma samples as a baseline before the study and then on the 4th day after each 3-day study arm. The absolute quantities of the markers will be analysed with Olink Target 48 Cytokine Panel (Olink Proteomics, Uppsala, Sweden). Differences in inflammation markers (from plasma)	after treatment (4th day)
Changes from Baseline in Calprotectin	Faecal calprotectin (from faecal sample) is used to measure inflammation status of the gut. Participants collect the first stool of the day in a collection tube and bring it to the study facility in a cooled bag after each study arm.	after treatment (4th day)
Changes from Baseline in Stool types and Bowel movements	The changes in bowel movements and stool consistency are recorded using a defecation record with the 7-step Bristol stool chart during the consumption of milks (on each study arm). Participant will record the time of the bowel movement and the dominant type of the stool. The Bristol types will be categorized as hard (types 1 and 2), normal (types 3, 4, and 5), or loose stools (types 6 and 7).	3 days during the treatment
Changes from Baseline in Gastrointestinal symptoms	Gastrointestinal symptoms (self-reported) as measured by a questionnaire. The questionnaire is divided into seven types of gastrointestinal discomfort, and also includes a possibility to describe a gastrointestinal discomfort outside these seven given alternatives. The severity of the symptoms is self-reported on a three-step scale. Participants fill the questionnaire during 3 days on the baseline and on each study arm (treatment).	3 days during the treatment
Changes from Baseline in high-sensitivity CRP	Inflammation marker high-sensitivity CRP is measured from fasting plasma samples as a baseline before the study and then on the 4th day after each 3-day study arm.	after treatment (4th day)

Collaborators and Investigators

• Sponsor: University of Turku

Publications and helpful links

General Publications

• Mannila E, Hokkanen L, Ahonen E, Turpeinen AM, Kalliomaki M, Kortesniemi M, Linderborg KM. Tolerance of protein-hydrolyzed lactose-free A1 milk and A2 milk in lactose-tolerant and lactose-intolerant volunteers: A randomized crossover trial with 2 parallel groups. J Dairy Sci. 2025 Sep;108(9):9062-9077. doi: 10.3168/jds.2025-26712. Epub 2025 Jul 3.

Study record dates

Study Major Dates

• Study Start (Actual): May 18, 2022
• Primary Completion (Actual): March 3, 2023
• Study Completion (Actual): March 3, 2023

Study Registration Dates

• First Submitted: March 22, 2022
• First Submitted That Met QC Criteria: March 22, 2022
• First Posted (Actual): March 31, 2022

Study Record Updates

• Last Update Posted (Actual): April 29, 2026
• Last Update Submitted That Met QC Criteria: April 23, 2026
• Last Verified: March 1, 2023

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Metabolism, Inborn Errors; Genetic Diseases, Inborn; Metabolic Diseases; Intestinal Diseases; Digestive System Diseases; Gastrointestinal Diseases; Malabsorption Syndromes; Carbohydrate Metabolism, Inborn Errors; Congenital, Hereditary, and Neonatal Diseases and Abnormalities; Nutritional and Metabolic Diseases; Lactose Intolerance; Therapeutics; Nutrition Therapy; Diet Therapy
• Other Study ID Numbers: MILK3

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Sensitive volunteer data may only be shared for collaborative research purposes with a separate agreement with the data owner.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No