Milk Containing A2 β-Casein ONLY, as a Single Meal, Causes Fewer Symptoms of Lactose Intolerance than Milk Containing A1 and A2 β-Caseins in Subjects with Lactose Maldigestion and Intolerance: A Randomized, Double-Blind, Crossover Trial.

Monica Ramakrishnan, Tracy K Eaton, Omer M Sermet, Dennis A Savaiano

Journal: Nutrients 2021;12(12):3855

PMID: 33348621

Plain Language Summary

Lactose intolerant people cannot digest a sugar molecule in milk called lactose, leading to uncomfortable symptoms like abdominal pain, bloating, flatulence, diarrhoea and faecal urgency. The symptoms may appear within a few hours of consuming the milk. Previous studies in the Chinese and Australian populations have shown that milk consumption containing only the A2 β-casein protein caused fewer lactose intolerance symptoms than milk containing both A1 and A2 β-casein protein. Casein is a protein abundant in milk. Conventional milk contains both A1 and A2 β-casein protein. The digestion of A1 β-casein protein releases a peptide called β-casomorphin-7, which may contribute to lactose intolerance symptoms. This randomised, double-blind, crossover single-meal trial aims to determine the tolerance of four different types of milk that contain A1 and A2 β-casein protein to varying concentrations among 33 people with lactose intolerance and maldigestion. The participants who consumed milk containing only A2 β-casein protein reported less abdominal pain than those who drank conventional milk or Jersey milk. The results of this study will need to be confirmed by further research in a larger population. Healthcare professionals can use this study when making dietary recommendations.

Abstract

Acute-feeding and multiple-day studies have demonstrated that milk containing A2 β-casein only causes fewer symptoms of lactose intolerance (LI) than milk containing both A1 and A2 β-caseins. We conducted a single-meal study to evaluate the gastrointestinal (GI) tolerance of milk containing different concentrations of A1 and A2 β-casein proteins. This was a randomized, double-blind, crossover trial in 25 LI subjects with maldigestion and an additional eight lactose maldigesters who did not meet the QLCSS criteria. Subjects received each of four types of milk (milk containing A2 β-casein protein only, Jersey milk, conventional milk, and lactose-free milk) after overnight fasting. Symptoms of GI intolerance and breath hydrogen concentrations were analyzed for 6 h after ingestion of each type of milk. In an analysis of the 25 LI subjects, total symptom score for abdominal pain was lower following consumption of milk containing A2 β-casein only, compared with conventional milk ( = 0.004). Post hoc analysis with lactose maldigesters revealed statistically significantly improved symptom scores ( = 0.04) and lower hydrogen production ( = 0.04) following consumption of milk containing A2 β-casein only compared with conventional milk. Consumption of milk containing A2 β-casein only is associated with fewer GI symptoms than consumption of conventional milk in lactose maldigesters.

Address: Department of Nutrition Science, College of Health and Human Sciences, Purdue University, West Lafayette, IN 47907, USA.

DOI: 10.3390/nu12123855

Patient Centred Factor

Triggers: A1 and A2 β-Caseins

Physical Environment

Infectious Agents

Clinical Imbalances

Gastro-intestinal

Modifiable Lifestyle Factors

Diet

Jadad Score

Allocation Concealment

Yes

Nutrition Evidence Keywords

A1 and A2 β-Caseins A2 β-Casein protein Lactose intolerance and maldigestion β-casomorphin-7

Bioactive Substances

A1 and A2 β-Casein Protein A2 β-Casein Protein β-casomorphin-7

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MeSH Terms: Abdominal Pain, Adult, Animals, Caseins, Cross-Over Studies, Diarrhea, Double-Blind Method, Feeding Behavior, Female, Flatulence, Humans, Lactose Intolerance, Male, Meals, Middle Aged, Milk, Young Adult