An interventional study of Lactose-Containing A1-Free Milk and Lactose-Containing Conventional Milk in Postprandial Glucose Response, Insulin Response and Lactose Digestion, sponsored by Purdue University. Not yet recruiting. Open to participants aged 18 Years to 65 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-05-05.
Sponsored by Purdue University · Not applicable, Interventional, and Other
This study will examine how different types of milk affect blood sugar and insulin responses after eating. Specifically, the study compares milk that contains only A2 beta-casein protein (A1-free milk) to conventional milk, which contains both A1 and A2 proteins.
Participants will complete four study visits in which they will consume different milk-based beverages. These include lactose-containing milk and lactose-free milk followed by a lactose drink given later. Blood samples will be collected over several hours to measure glucose and insulin responses. Breath tests and questionnaires will also be used to assess digestion and gastrointestinal symptoms.
The goal of this study is to determine whether milk protein type influences metabolic responses and whether consuming lactose-free milk affects how the body processes lactose when it is consumed later.
Postprandial glucose and insulin responses are important indicators of metabolic health, even in individuals without diagnosed metabolic disease. The rate and pattern of nutrient digestion and absorption can influence these responses, and emerging evidence suggests that differences in milk protein composition, specifically the presence or absence of A1 beta-casein, may alter gastrointestinal function and metabolic outcomes.
This study is a randomized, double-blind, crossover trial designed to evaluate the effects of A1-free milk compared to conventional milk on postprandial metabolic responses in healthy adults. Participants will complete four experimental conditions in random order: (1) lactose-containing A1-free milk, (2) lactose-containing conventional milk, (3) lactose-free A1-free milk followed by a delayed lactose challenge, and (4) lactose-free conventional milk followed by a delayed lactose challenge.
The inclusion of both lactose-containing and lactose-free conditions allows for evaluation of two complementary questions. First, direct comparisons between lactose-containing A1-free and conventional milk will assess whether milk protein composition influences postprandial glucose and insulin responses under typical consumption conditions. Second, the lactose-free preload conditions, combined with a standardized delayed lactose challenge, are designed to evaluate whether prior milk consumption modifies subsequent metabolic responses to lactose exposure. This approach provides insight into potential differences in digestive kinetics, including gastric emptying, nutrient delivery, and lactose digestion and absorption.
During each study visit, participants will consume a standardized milk-based intervention following an overnight fast. In the lactose-free conditions, a lactose beverage matched to the amount of lactose typically present in the milk will be administered 60 minutes after milk consumption. Blood samples will be collected at multiple timepoints over a postprandial period to measure glucose and insulin concentrations and characterize response patterns, including early-phase responses and overall exposure.
Secondary and exploratory outcomes include breath hydrogen testing as a non-invasive marker of carbohydrate fermentation and lactose maldigestion, as well as gastrointestinal symptom assessments using validated questionnaires. These measures will be used to provide additional context for interpreting metabolic responses across conditions.
The crossover design allows each participant to serve as their own control, improving statistical power and reducing variability. The findings from this study will help clarify whether differences in milk protein composition influence metabolic responses and whether prior exposure to lactose-free milk alters the body's handling of lactose consumed at a later time.
Purdue University is the lead sponsor of 168 studies on the registry; 23 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Exclusion Criteria:
Participants consume lactose-containing A1-free milk during one study visit. Blood, breath hydrogen, urine, and gastrointestinal symptom measures are collected over the 180 minute postprandial period.
Dietary Supplement: Lactose-Containing A1-Free Milk
Participants consume lactose-containing conventional milk containing both A1 and A2 beta-casein during one study visit. Blood, breath hydrogen, urine, and gastrointestinal symptom measures are collected over the 180 minute postprandial period.
Dietary Supplement: Lactose-Containing Conventional Milk
Participants consume lactose-free A1-free milk followed by a lactose drink administered 60 minutes after milk consumption. Blood, breath hydrogen, and gastrointestinal symptom measures are collected over the 180 minute postprandial period.
Dietary Supplement: Lactose-Free A1-Free Milk With Delayed Lactose Drink
Participants consume lactose-free conventional milk containing both A1 and A2 beta-casein followed by a lactose drink administered 60 minutes after milk consumption. Blood, breath hydrogen, and gastrointestinal symptom measures are collected over the 180 minute postprandial period.
Dietary Supplement: Lactose-Free Conventional Milk With Delayed Lactose Drink
A lactose-containing milk beverage containing A2 beta-casein and no A1 beta-casein, consumed during one experimental study visit.
Also known as: A1-free milk, A2 milk
A lactose-containing conventional milk beverage containing both A1 and A2 beta-casein, consumed during one experimental study visit.
Also known as: Conventional milk, A1/A2 milk
A lactose-free A1-free milk beverage consumed at the start of the study visit, followed by a lactose drink administered 60 minutes after milk consumption. The lactose drink is matched to the amount of lactose expected in the milk serving.
A lactose-free conventional milk beverage containing both A1 and A2 beta-casein consumed at the start of the study visit, followed by a lactose drink administered 60 minutes after milk consumption. The lactose drink is matched to the amount of lactose expected in the milk serving.
Postprandial Plasma Insulin Incremental Area Under the Curve (iAUC)
Incremental area under the curve (iAUC) for plasma insulin concentrations following consumption of each study condition, measured from serial blood samples collected via an indwelling catheter.
Time frame: 0 to 180 minutes post-intervention during each study visit
Postprandial Plasma Glucose Incremental Area Under the Curve (iAUC)
Incremental area under the curve (iAUC) for plasma glucose concentrations following consumption of each study condition, measured from serial blood samples collected via an indwelling catheter.
Time frame: 0 to 180 minutes post-intervention during each study visit
Early-Phase Postprandial Glucose and Insulin Response
Early-phase postprandial response assessed by incremental area under the curve (iAUC) for plasma glucose and insulin concentrations.
Time frame: 0 to 60 minutes post-intervention
Time to Peak Plasma Glucose and Insulin Concentrations (Tmax)
Time required to reach peak plasma glucose and insulin concentrations following each study condition.
Time frame: 0 to 180 minutes post-intervention
Circulating Metabolite Responses
Postprandial changes in circulating metabolites, including amino acids and acylcarnitines, measured from plasma samples to assess metabolic responses.
Time frame: 0, 30, 60, and 120 minutes
Breath Hydrogen Concentrations
Breath hydrogen levels measured as a non-invasive marker of carbohydrate fermentation and lactose maldigestion.
Time frame: Baseline and every 30 minutes from 0 to 180 minutes post-intervention
Gastrointestinal Symptom Scores
Self-reported gastrointestinal symptoms (e.g., bloating, gas, abdominal discomfort) assessed using visual analog scale and Likert-type questionnaires.
Time frame: Baseline and at 60, 120, and 180 minutes post-intervention
Urinary Galactose Concentrations
Urinary galactose concentrations measured as an marker of lactose metabolism.
Time frame: Baseline and 180 minutes post intervention
No study locations are listed for this record.
Plan to share: No
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