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Milk Intolerance, Beta-Casein and Lactose

1
School of Public Health, Curtin Health Innovation Research Institute, Curtin University, GPO Box U1987, Perth WA 6845, Australia
2
Agricultural Management Group, Lincoln University, PO Box 85084, Lincoln 7647, Christchurch, New Zealand
3
The a2 Milk Company (Australia) Pty Ltd, PO Box 180, Kew East, Victoria 3102, Australia
*
Author to whom correspondence should be addressed.
Nutrients 2015, 7(9), 7285-7297; https://doi.org/10.3390/nu7095339
Received: 2 July 2015 / Revised: 12 August 2015 / Accepted: 21 August 2015 / Published: 31 August 2015
(This article belongs to the Special Issue Lactose Intolerance: Biology, Genetics and Dietary Management)
True lactose intolerance (symptoms stemming from lactose malabsorption) is less common than is widely perceived, and should be viewed as just one potential cause of cows’ milk intolerance. There is increasing evidence that A1 beta-casein, a protein produced by a major proportion of European-origin cattle but not purebred Asian or African cattle, is also associated with cows’ milk intolerance. In humans, digestion of bovine A1 beta-casein, but not the alternative A2 beta-casein, releases beta-casomorphin-7, which activates μ-opioid receptors expressed throughout the gastrointestinal tract and body. Studies in rodents show that milk containing A1 beta-casein significantly increases gastrointestinal transit time, production of dipeptidyl peptidase-4 and the inflammatory marker myeloperoxidase compared with milk containing A2 beta-casein. Co-administration of the opioid receptor antagonist naloxone blocks the myeloperoxidase and gastrointestinal motility effects, indicating opioid signaling pathway involvement. In humans, a double-blind, randomized cross-over study showed that participants consuming A1 beta-casein type cows’ milk experienced statistically significantly higher Bristol stool values compared with those receiving A2 beta-casein milk. Additionally, a statistically significant positive association between abdominal pain and stool consistency was observed when participants consumed the A1 but not the A2 diet. Further studies of the role of A1 beta-casein in milk intolerance are needed. View Full-Text
Keywords: milk consumption; lactose; beta-casein; lactose intolerance milk consumption; lactose; beta-casein; lactose intolerance
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Pal, S.; Woodford, K.; Kukuljan, S.; Ho, S. Milk Intolerance, Beta-Casein and Lactose. Nutrients 2015, 7, 7285-7297.

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