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

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 (p = 0.004). Post hoc analysis with lactose maldigesters revealed statistically significantly improved symptom scores (p = 0.04) and lower hydrogen production (p = 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.

Keywords: A1 beta-casein; A2 beta-casein; Qualifying Lactose Challenge Symptom Score; beta-casomorphin; gastrointestinal intolerance; hydrogen breath test; lactose challenge; lactose intolerance symptoms; milk intolerance.

Conflict of interest statement

The authors declare no potential conflicts of interest during the conduct of this study.

Figures

Figure 1

Study enrollment, randomization and analyses. HBT, hydrogen breath test; LI, lactose intolerance/intolerant.

Figure 2

Total symptoms reported during the 6 h after consuming the four milk products in 25 lactose intolerant subjects. ** p = 0.004 for abdominal pain due to milk containing A2 β-casein only vs. conventional milk.

Figure 3

Total symptoms reported during the 6 h after consuming the four milk products in 33 lactose maldigesters. ** p = 0.001 for abdominal pain and * p = 0.04 for total symptoms (abdominal pain + bloating + flatulence + diarrhea) due to milk containing A2 β-casein only vs. conventional milk; † p = 0.05 for bloating due to Jersey milk versus conventional milk.

Figure 4

Total hydrogen produced during the 6 h after consuming the four milk products in 25 lactose intolerant subjects. ppm, parts per million. † p = 0.05, † p = 0.03, † p = 0.01, and † p = 0.05 for Jersey milk vs. commercial milk at 0, 0.5, 2, and 3 h, respectively.

Figure 5

Total hydrogen produced during the 6 h after consuming the four milk products in 33 lactose maldigesters. ppm, parts per million. * p = 0.05, * p = 0.03 for milk containing A2 β-casein only vs. conventional milk at 3 and 4 h, respectively; † p = 0.03 for Jersey milk versus conventional milk at 2 h.