Milk Intolerance Lactose-free Knowledge (MILK) Trial, the effect of A1-protein-free lactose-free milk compared to conventional lactose-free milk in adults who identify as lactose intolerant.
Effect of A1-protein free lactose-free milk on markers of inflammation, immune response and cognitive function, as compared to conventional lactose-free milk which contains both A1/A2 type beta-casein proteins, in adults who drink lactose-free milk due to self-perceived lactose intolerance.
FOODiQ Global
124 participants
Sep 10, 2025
Interventional
Conditions
Summary
Lactose intolerance results from reduced activity of the lactase enzyme, leading to incomplete digestion of lactose and fermentation by gut microbiota, which can produce symptoms such as bloating, pain, and discomfort. While lactose malabsorption is common globally, symptoms occur in only a subset of individuals and self-reported lactose intolerance often does not align with objective clinical diagnosis. Lactose-free milk products have been developed to address lactose malabsorption, however, research shows inconsistent effects on gastrointestinal symptoms. Emerging evidence suggests that intolerance symptoms attributed to lactose may also be influenced by other milk components, particularly the A1 beta-casein protein. This study will investigate the effects of A1-protein-free lactose-free milk compared with conventional lactose-free milk in individuals with self-perceived lactose intolerance. Outcomes will include gastrointestinal symptoms and markers of inflammation and immune response. The study hypothesises that A1-protein-free lactose-free milk will improve tolerance and reduce symptoms compared with conventional lactose-free milk, while maintaining the nutritional benefits of dairy consumption.
Eligibility
Inclusion Criteria13
- Ability/desire to provide informed consent.
- Adults aged 18+ years.
- Any sex or gender.
- BMI: 18.5-35 kg/m2 inclusive.
- Understand written and spoken English.
- Self-reported intolerance to cows’ milk, via digestive discomfort after consuming lactose-containing milk.
- Currently consuming conventional lactose-free cows’ milk.
- Reside in the Brisbane metropolitan area for the duration of the study.
- Willing to attend all study visits and complete all study related procedures.
- Agree to avoid prebiotic and probiotic supplements during the study period.
- Willing to consume 500 mL of full cream lactose-free cows’ milk daily during the intervention periods (250 mL in the morning and 250 mL in the afternoon or evening).
- Agree to avoid all dairy products, including other milk not provided by the study.
- Be willing to follow a dairy exclusion diet (except the intervention milk provided by the study) and refrain from products used for lactose, milk or dairy intolerance (e.g., Lactaid® dietary supplements) throughout all washout and trial phases of the study.
Exclusion Criteria18
- Unable to provide informed consent.
- Clinically confirmed allergic reaction to cows’ milk.
- Diagnosed with one or more of the following conditions:
- A chronic disease, including autoimmune conditions, kidney or liver disease, cardiovascular disease, and diabetes.
- An inflammatory bowel disorder, including Crohn’s or ulcerative colitis. Controlled coeliac disease or functional bowel disorders (i.e., irritable bowel syndrome (IBS), functional bloating, functional diarrhoea, functional constipation and unspecified functional bowel disorders) will not be excluded due to no obvious inflammation within the digestive track.
- Disorders known to be associated with abnormal gastrointestinal motility (i.e., gastroparesis, neuromuscular diseases, collagen vascular diseases, alcoholism, uraemia, malnutrition or untreated hypothyroidism)
- Clinically diagnosed mental health conditions, including major depressive disorder, psychotic disorder such as schizophrenia, anorexia nervosa, bulimia nervosa, substance abuse disorder, bipolar disorder, personality disorder.
- Pregnant, breastfeeding, or attempting to become pregnant.
- Regular smoker of cigarettes, tobacco, or user of nicotine-containing products.
- Hospitalised within the past 1-month for any reason.
- Vaccination within 30 days of trial commencement (or during the trial).
- Recent infection within 30 days of trial commencement (and notify investigators if contracted during the trial)
- Recent use of systemic antibiotics, defined as use within 30 days prior to screening.
- Use of prescribed or recreational drugs, including steroids, CBD or cannabis, NSAIDs, or proton-pump inhibitors, within the past 2 months.
- Over-the-counter prescriptions permitted unless otherwise listed above or known to impact immunity and systemic inflammation.
- Participants that have used antihistamines or paracetamol in the past 7 days will be temporarily excluded from beginning the trial and requested to abstain from their use throughout the study
- Currently participating in another biomedical or medical study.
- Any other conditions/issues noted by study staff and/or Principal Investigator that would impact participation and/or protocol compliance (e.g. participant does not have reliable access to refrigeration, participant interview reveals safety concerns due to previous history of fainting with needles)
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Interventions
250 mL A1 protein-free, lactose-free, full cream (3.5% fat) cows milk (A2 lactose free), consumed twice per day, morning and evening, after a meal, for 14 days. Fresh milk will be delivered directly to participants weekly during the study periods via courier. Participants will be required to store the fresh milk at refrigerator temperature, and can consume the milk during the course of their normal daily activities. Participants are asked to avoid all dairy products other than those provided in the study for the duration of the study, which includes a 14-day run-in period, and 14-day washout period between intervention periods. Compliance will be monitored through participant reporting and dietary records collected during the study.
Locations(1)
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ACTRN12626000392369