Food and Behaviour Research

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06 August 2014 - questioning-answers - Gastrointestinal response to A1 vs A2 milk

Paul Whiteley
I want to talk about the findings from Ho and colleagues today, and in particular their observation of: "differences in gastrointestinal responses in some adult humans consuming milk containing beta-casein of either the A1 or the A2 beta-casein type".

If you're wondering why such a paper finds it's way on to a blog predominantly about autism research, well stay with me on this rather long blogging entry...
  • First things first, this was a double-blind, randomised cross-over study looking at "gastrointestinal effects" in adults under conditions of either A1 or A2 milk consumption. Two weeks of either A1 or A2 milk consumption (with an appropriate washout period in between) were completed.
  • The very informative Bristol Stool Chart was used to grade poop (stool) consistency alongside other more physiological measures such as faecal calprotectin.
  • Results: "The A1 beta-casein milk led to significantly higher stool consistency values". That and a correlation between stool consistency and reports of abdominal pain for participants when on the A1 milk compared with when on A2 milk. Ergo, it didn't seem that A2 milk did anything over and above A1 milk, rather that consumption didn't seem to be linked to the symptoms noted when drinking A1 milk. 
Appreciating the authors' call for further study in this area, I was intrigued by these results. Not so many moons ago, I came across the paper by Barnett and colleagues talking about greater gastrointestinal (GI) transit time in rats fed A1 milk over A2 milk. One might very well overlap those rodent reports with the more recent Ho results in terms of how longer transit time from A1 milk might mean greater discomfort bearing in mind some of the literature on longer transit time and "pain and distension" in certain conditions.

As per my previous caveat, I don't think we are in a position yet to advocate changes in milk drinking practices for specific groups based on the available literature, but there might be quite a bit more research to do in this important area.