Unspecified milk intolerance in the absence of cows' milk protein allergy is reported to affect up to 20% of UK adults. The lay assumption of this phenomenon is lactose intolerance.
However the prevalence of lactose intolerance in Europe is quite low, attributed to the persistence of lactase activity into adulthood, reports suggest that <5% of the UK are clinically diagnosed as lactose intolerant.
Two randomised controlled trials have been conducted to date that suggest the removal of A1 beta-casein, found in regular cows' milk and substitution with a2 Milk™ can help with the management of gastrointestinal disturbance associated with regular cows' milk intake.
Trial 1. Ho and colleagues (2014) conducted a randomised, double blind, cross-over trial for 6 weeks with 33 non-milk intolerant and 8 self-assessed milk intolerant participants.
All were provided with milk containing 100% A1 beta-casein or 100% A2 beta-casein (a2 Milk™) for 2 weeks, followed by a washout period of rice milk for 2 weeks. All participants then crossed over to receive the opposing milk for 2 weeks.
- Gastrointestinal inflammation using faecal calprotectin was overall, higher in participants when they drank 100% A1 beta-casein milk compared to a2 Milk™.
- Gastrointestinal symptoms: bloating, abdominal pain, flatulence and difficulty voiding were worse for participants when they drank 100% A1 beta-casein milk compared to a2 Milk™.
- Stool consistency and bowel frequency were higher when drinking 100% A1 beta-casein milk. This infers softer stools, trending towards diarrhoea. a2 Milk™ produced no change in stool consistency.
Trial 2. Sun et al. (2016) recruited 45 healthy participants in Shanghai, China with a history of self-reported milk intolerance into a double-blind, randomised, 8-week cross-over study. Following a 2 week washout period with rice milk, participants had 2 weeks of drinking conventional cows' milk (A1 beta-casein containing) before undergoing another 2 week washout period. This was then followed by 2 weeks of drinking a2 Milk™. Twenty three of the 45 were clinically diagnosed as lactase deficient (urinary galactose analysis), the authors reporting this as lactose intolerance.
- SMART pill assessment showed a visual increase in gastrointestinal inflammation when the participants drank regular cows' milk. This was also confirmed by serum marker (CRP, Hb, IL-4, IgG1, IgG2a, IgE & GSH) and faecal analysis (SCFA, MPO). When the participants switch to a2 Milk™, all markers improved towards baseline.
- SMART pill confirmed a reduction in mean whole gut transit time by 6.6 hours when participants drank regular cows' milk. a2 Milk™ was comparable to baseline in all participants, no significant impact on gut transit.
- Visual Analog Scale assessment of bloating, flatulence, borborygmus and abdominal pain were all rated as worse when participants drank regular milk. Symptoms were highest in those with lactose intolerance as expected. a2 Milk™ did not trigger symptoms in any participants, including those with lactose intolerance.
- A Subtle Cognitive Impairment Test demonstrated that participants who drank regular cows' milk had a 2.76% error rate and were 14.7 milliseconds slower in terms of reaction time than those drinking a2 Milk™
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