Prolonged Consumption of A2 ß-Casein Milk Reduces Symptoms Compared to A1 and A2 ß-Casein Milk in Lactose Maldigesters: A Two-Week Adaptation Study.

Approximately 30% of milk protein is ß-casein. We aimed to determine whether lactose maldigesters who chronically consumed two cups of A1/A2 milk (containing 75% A1 ß-casein and 25% A2 ß-casein) would adapt to have fewer intolerance symptoms, lower serum inflammatory markers, and/or altered glutathione levels similar to those consuming A2 milk (containing 100% A2 ß-casein). A double-blinded, randomized, crossover trial was conducted. Sixteen confirmed lactose maldigesters consumed 250 mL of A1/A2 milk and A2 milk twice daily with meals for two weeks. At the end of the adaptation period on day 15, lactose maldigestion was measured after a challenge with the same milk used for adaptation (0.5 g of lactose per kg of body weight) with a hydrogen breath test. Fecal urgency was higher during the two-week consumption of A1/A2 milk compared to A2 milk (p = 0.04, n = 16). Bloating (p = 0.03, n = 16) and flatulence (p = 0.02, n = 16) were also higher on the 15th day with A1/A2 milk compared to A2 milk challenge. However, day-to-day symptoms, hydrogen, serum inflammatory markers, and antioxidant concentrations were not different after A1/A2 and A2 milk consumption adaptation periods. Adaptation over two weeks did not improve lactose digestion or tolerance of A1/A2 milk to match that of A2 milk.

Gastric Emptying of New-World Milk Containing A1 and A2 Β-Casein Is More Rapid as Compared to Milk Containing Only A2 Β-Casein in Lactose Maldigesters: A Randomized, Cross-Over Trial Using Magnetic Resonance Imaging.

Lactose maldigesters report an increase in abdominal pain due to the consumption of milk containing a mixture of A1 and A2 ß-casein as compared to milk containing only A2 ß-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 ß-casein and 25% A2 ß-casein and A2 milk containing 100% A2 ß-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 ß-casein and 25% A2 ß-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 ß-casein in the 10 lactose maldigesters. The transit of New-World milk containing A1 and A2 ß-casein was more rapid as compared to Old-World milk containing only A2 ß-casein. This difference in transit may mediate symptoms of lactose intolerance.

Relationships of Intestinal Lactase and the Small Intestinal Microbiome with Symptoms of Lactose Intolerance and Intake in Adults.

BACKGROUND: Approximately two-thirds of adults are genetically predisposed to decreased lactase activity after weaning, putting them at risk of lactose intolerance. However, symptoms are a poor marker of lactose maldigestion. AIMS: We assessed association between self-reported lactose intolerance and intestinal lactase, lactose intake, and the small intestinal microbiome. METHODS: Patients 18-75 years presenting for upper endoscopy were recruited prospectively. Observational study participants completed a lactose intolerance symptom questionnaire and reported lactose intake. Post-bulbar biopsies were obtained to measure lactase activity and assess the small intestinal mucosal microbiome. We compared intestinal lactase between patients with and without lactose intolerance. We assessed associations between lactose intolerance symptoms and lactase and lactose intake. We examined associations of small bowel microbial composition with self-reported lactose intolerance and symptoms. RESULTS: Among 34 patients, 23 (68%) reported lactose intolerance. Those with lactose intolerance had higher total symptom scores, more frequent bowel urgency, and more bowel movements after consuming dairy. The proportion of individuals with abnormal lactase activity did not differ by lactose intolerance status. Median lactase levels were correlated with total lactose intolerance symptom scores (p = 0.038) and frequency of bowel urgency (p = 0.012). Daily lactose intake did not differ between groups. In 19 patients, we observed significant associations of small intestinal microbiome beta diversity with stool consistency after consuming dairy (p = 0.03). CONCLUSIONS: Intestinal lactase is associated with lactose intolerance symptoms and bowel urgency in adults but does not distinguish the clinical phenotype entirely. Studying other contributing factors (microbiota, diet) may further clarify the pathophysiology of lactose intolerance.

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

Acute-feeding and multiple-day studies have demonstrated that milk containing A2 ß-casein only causes fewer symptoms of lactose intolerance (LI) than milk containing both A1 and A2 ß-caseins. We conducted a single-meal study to evaluate the gastrointestinal (GI) tolerance of milk containing different concentrations of A1 and A2 ß-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 ß-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 ß-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 ß-casein only compared with conventional milk. Consumption of milk containing A2 ß-casein only is associated with fewer GI symptoms than consumption of conventional milk in lactose maldigesters.