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.

Lactose maldigesters report an increase in abdominal pain due to the consumption of milk containing a mixture of A1 and A2 β-casein as compared to milk containing only A2 β-casein. Gastric transit affects gastrointestinal symptoms and rapid transit has been associated with an increase in abdominal pain. We conducted a double-blinded, randomized, crossover trial in 10 lactose maldigesters. Subjects consumed each of the two types of milk: conventional milk containing 75% A1 β-casein and 25% A2 β-casein and A2 milk containing 100% A2 β-casein. Magnetic resonance images were acquired, and abdominal pain was rated and recorded at 0, 10, 30, 60 and 120 min after milk consumption. The volume of milk in the stomach was calculated using FSL software. The volume of milk in the stomach after consuming milk with 75% A1 β-casein and 25% A2 β-casein was significantly lower at 30 (p = 0.01), 60 (p = 0.002) and 120 (p < 0.001) minutes as compared to milk with 100% A2 β-casein in the 10 lactose maldigesters. The transit of New-World milk containing A1 and A2 β-casein was more rapid as compared to Old-World milk containing only A2 β-casein. This difference in transit may mediate symptoms of lactose intolerance.

No abstract

Objectives To compare the gastric transit time of milk containing A1 beta-casein and milk containing only A2 beta-casein in lactose maldigesters. Methods We conducted a double-blinded, randomized, crossover trial. Subjects consumed each of the two types of milk: conventional New World milk containing 75% A1 beta-casein and 25% A2 beta-casein and Old World milk containing 100% A2 beta-casein, matched for macronutrient composition. Magnetic Resonance Imaging (MRI) images were acquired and symptoms were rated and recorded at 0, 10, 30, 60 and 120 minutes after consumption. Images were analyzed with FSL software and the volume of milk (ml) in stomach at 0, 10, 30, 60 and 120 minutes was calculated. Results The volume of milk in the stomach after consuming A1 milk was significantly lower at 10 (P = 0.04), 30 (P = 0.07), 60 (P = 0.04) and 120 (P = 0.001) minutes as compared to A2 milk (N = 6), demonstrating more rapid transit. Conclusions There is more rapid transit after consumption of New World milk containing A1 beta-casein. This difference in transit may mediate symptoms of lactose intolerance. Funding Sources Gift funds from A2 milk company.