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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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.

It is difficult for adults to achieve the DRI for calcium without consuming dairy products; therefore, aversion to and avoidance of milk and dairy products puts US adults in danger of calcium deficiency. We examined whether a 21 day milk drinking intervention could reverse milk aversion in people who do not habitually consume milk due to lactose intolerance (LI), perceived LI or taste aversion. 445 potential participants responded to advertisements; 82 were screened, 27 completed the milk drinking intervention, 26 completed the 3 month follow up and 24 completed the 6 month follow up. Participants who entered the milk drinking phase were instructed to consume increasing amounts of liquid cow’s milk for a period of 21 days up to 1 cup two times/day with a pre and post hydrogen breath test. The lactose digesters and maldigesters both showed a decrease in overall symptom scores, with no significant difference between groups. Independent of digestive status, subjects demonstrated a significant decrease in aversion, an increase in likeness and an increase in milk and overall calcium consumption at 3 and 6 month following the intervention. These changes in milk consumption were independent of demographics or digestive status. The data reported here suggest a reversal of food avoidance and the possibility that milk avoiders are able to increase likeness and incorporate milk into their diet after increased exposure.