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.
Objectives
We evaluated tolerance to single meals of milks containing different levels of a1 and a2 β-casein as compared to lactose-free milk. We also determined if lactose digestion was affected by a2, high a2 (Jersey) and high a1 (commercial) β-casein milks, as measured by breath hydrogen.
Methods
A double-blinded, randomized crossover trial was conducted in 21 verified lactose intolerant subjects, feeding four milks (commercial, Jersey, a2 and commercial lactose free) after an overnight fast. Breath hydrogen was measured, and intolerance symptoms were recorded for 6 hours following treatment.
Results
Mean hydrogen production and total symptoms were significantly lower following consumption of a2 milk as compared to commercial milk (P = 0.03 for both). Similarly, high a2 Jersey milk produced significantly lower hydrogen than commercial milk (P = 0.01). However, symptoms due to Jersey were not significantly different from commercial milk (P = 0.47).
Conclusions
A2 milk caused fewer symptoms and lower gas production in verified lactose intolerant subjects.
Funding Sources
Gift funds from the a2 Milk Company.
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