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Effects of milk containing only A2 beta casein versus milk containing both A1 and A2 beta casein proteins on gastrointestinal physiology, symptoms of discomfort, and cognitive behavior of people with self-reported intolerance to traditional cows' milk.

ABSTRACT: Cows' milk generally contains two types of ?-casein, A1 and A2 types. Digestion of A1 type can yield the peptide ?-casomorphin-7, which is implicated in adverse gastrointestinal effects of milk consumption, some of which resemble those in lactose intolerance. This study aimed to compare the effects of milk containing A1 ?-casein with those of milk containing only A2 ?-casein on inflammation, symptoms of post-dairy digestive discomfort (PD3), and cognitive processing in subjects with self-reported lactose intolerance.Forty-five Han Chinese subjects participated in this double-blind, randomized, 2 × 2 crossover trial and consumed milk containing both ?-casein types or milk containing only A2 ?-casein. Each treatment period was 14 days with a 14-day washout period at baseline and between treatment periods. Outcomes included PD3, gastrointestinal function (measured by smart pill), Subtle Cognitive Impairment Test (SCIT), serum/fecal laboratory biomarkers, and adverse events.Compared with milk containing only A2 ?-casein, the consumption of milk containing both ?-casein types was associated with significantly greater PD3 symptoms; higher concentrations of inflammation-related biomarkers and ?-casomorphin-7; longer gastrointestinal transit times and lower levels of short-chain fatty acids; and increased response time and error rate on the SCIT. Consumption of milk containing both ?-casein types was associated with worsening of PD3 symptoms relative to baseline in lactose tolerant and lactose intolerant subjects. Consumption of milk containing only A2 ?-casein did not aggravate PD3 symptoms relative to baseline (i.e., after washout of dairy products) in lactose tolerant and intolerant subjects.Consumption of milk containing A1 ?-casein was associated with increased gastrointestinal inflammation, worsening of PD3 symptoms, delayed transit, and decreased cognitive processing speed and accuracy. Because elimination of A1 ?-casein attenuated these effects, some symptoms of lactose intolerance may stem from inflammation it triggers, and can be avoided by consuming milk containing only the A2 type of beta casein.ClinicalTrials.gov/NCT02406469.

SUBMITTER: Jianqin S

PROVIDER: S-EPMC4818854 | biostudies-literature | 2016 Apr

REPOSITORIES: biostudies-literature

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Effects of milk containing only A2 beta casein versus milk containing both A1 and A2 beta casein proteins on gastrointestinal physiology, symptoms of discomfort, and cognitive behavior of people with self-reported intolerance to traditional cows' milk.

Jianqin Sun S Leiming Xu X Lu Xia X Yelland Gregory W GW Ni Jiayi J Clarke Andrew J AJ

Nutrition journal 20160402

<h4>Background</h4>Cows' milk generally contains two types of β-casein, A1 and A2 types. Digestion of A1 type can yield the peptide β-casomorphin-7, which is implicated in adverse gastrointestinal effects of milk consumption, some of which resemble those in lactose intolerance. This study aimed to compare the effects of milk containing A1 β-casein with those of milk containing only A2 β-casein on inflammation, symptoms of post-dairy digestive discomfort (PD3), and cognitive processing in subject ...[more]

PMID: 27039383

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Project description:A major protein component of cow's milk is ?-casein. The most frequent variants in dairy herds are A1 and A2. Recent studies showed that milk containing A1 ?-casein promoted intestinal inflammation and exacerbated gastrointestinal symptoms. However, the acute gastrointestinal effects of A1 ?-casein have not been investigated. This study compared the gastrointestinal effects of milk containing A1 and A2 ?-casein versus A2 ?-casein alone in Chinese adults with self-reported lactose intolerance.In this randomised, crossover, double-blind trial, with a 3-day dairy washout period at baseline, subjects were randomised to consume 300 mL of milk containing A1 and A2 ?-casein (ratio 58:42; conventional milk) or A2 ?-casein alone; subjects consumed the alternative product after a 7-day washout period. Urine galactose was measured at baseline after a 15 g lactose load. Subjects completed 9-point visual analogue scales for gastrointestinal symptoms (borborygmus, flatulence, bloating, abdominal pain, stool frequency, and stool consistency) at baseline and at 1, 3, and 12 h after milk consumption.A total of 600 subjects were included. All six symptom scores at 1 and 3 h were significantly lower after consuming A2 ?-casein versus conventional milk (all P<0.0001). At 12 h, significant differences remained for bloating, abdominal pain, stool frequency, and stool consistency (all P<0.0001). Symptom scores were consistently lower with A2 ?-casein in both lactose absorbers (urinary galactose ?0.27 mmol/L) and lactose malabsorbers (urinary galactose <0.27 mmol/L).Milk containing A2 ?-casein attenuated acute gastrointestinal symptoms of milk intolerance, while conventional milk containing A1 ?-casein reduced lactase activity and increased gastrointestinal symptoms compared with milk containing A2 ?-casein. Thus, milk-related gastrointestinal symptoms may result from the ingestion of A1 ?-casein rather than lactose in some individuals.NCT02878876 , registered August 16, 2016. Retrospectively registered.

Dataset Information

Effects of milk containing only A2 beta casein versus milk containing both A1 and A2 beta casein proteins on gastrointestinal physiology, symptoms of discomfort, and cognitive behavior of people with self-reported intolerance to traditional cows' milk.

Publications

Effects of milk containing only A2 beta casein versus milk containing both A1 and A2 beta casein proteins on gastrointestinal physiology, symptoms of discomfort, and cognitive behavior of people with self-reported intolerance to traditional cows' milk.

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