Comparative Effects of A1 Versus A2 Beta-Casein on Gastrointestinal Measures: a Blinded Randomised Cross-Over Pilot Study
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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.
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Comparative effects of A1 versus A2 beta-casein on gastrointestinal measures: a blinded randomised cross-over pilot studyHo, S.; Woodford, K.; Kukuljan, S.; Pal, Sebely (2014)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 ...
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