Comparative effects of A1 versus A2 beta-casein on gastrointestinal measures: a blinded randomised cross-over pilot study

• Published in: European journal of clinical nutrition Vol. 68; no. 9; pp. 994 - 1000
• Main Authors: Ho, S, Woodford, K, Kukuljan, S, Pal, S
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.09.2014; Nature Publishing Group
• Subjects: 692/699/1503; 692/700/2814; Abdominal Pain - etiology; Adult; Aged; Animals; Biological and medical sciences; Casein; Caseins - pharmacology; Cattle; Clinical Nutrition; Consistency; Cow's milk; Cross-Over Studies; Diet; Digestion - drug effects; Digestive system; Double-Blind Method; Endorphins - metabolism; Epidemiology; Feces; Feeding. Feeding behavior; Female; Fundamental and applied biological sciences. Psychology; Gastric motility; Gastroenterology; Gastrointestinal system; Gastrointestinal tract; Gastrointestinal Tract - drug effects; Gastrointestinal Tract - metabolism; Humans; Internal Medicine; Intolerance; Lactose intolerance; Leukocyte L1 Antigen Complex - metabolism; Male; Medical sciences; Medicine; Medicine & Public Health; Metabolic Diseases; Middle Aged; Milk; Milk - chemistry; original-article; Pain; Peptide Fragments - metabolism; Physiological aspects; Physiological research; Pilot Projects; Properties; Proteins; Public Health; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Young Adult; Randomization; Casein; Dicotyledones; Angiospermae; Metabolic diseases; Spermatophyta; Gastrointestinal; Crossover study; Comparative study; Chenopodiaceae; Beta
• ISSN: 0954-3007; 1476-5640; 1476-5640
• DOI: 10.1038/ejcn.2014.127

Background/objectives: At present, there is debate about the gastrointestinal effects of A1-type beta-casein protein in cows’ milk compared with the progenitor A2 type. In vitro and animal studies suggest that digestion of A1 but not A2 beta-casein affects gastrointestinal motility and inflammation through the release of beta-casomorphin-7. We aimed to evaluate differences in gastrointestinal effects in a human adult population between milk containing A1 versus A2 beta-casein. Subjects/methods: Forty-one females and males were recruited into this double-blinded, randomised 8-week cross-over study. Participants underwent a 2-week dairy washout (rice milk replaced dairy), followed by 2 weeks of milk (750 ml/day) that contained beta-casein of either A1 or A2 type before undergoing a second washout followed by a final 2 weeks of the alternative A1 or A2 type milk. Results: The A1 beta-casein milk led to significantly higher stool consistency values (Bristol Stool Scale) compared with the A2 beta-casein milk. There was also a significant positive association between abdominal pain and stool consistency on the A1 diet ( r =0.520, P =0.001), but not the A2 diet ( r =−0.13, P =0.43). The difference between these two correlations (0.52 versus −0.13) was highly significant ( P <0.001). Furthermore, some individuals may be susceptible to A1 beta-casein, as evidenced by higher faecal calprotectin values and associated intolerance measures. Conclusions: These preliminary results suggest differences in gastrointestinal responses in some adult humans consuming milk containing beta-casein of either the A1 or the A2 beta-casein type, but require confirmation in a larger study of participants with perceived intolerance to ordinary A1 beta-casein-containing milk.