Milk protein from the high-producing Holstein cows source of lactose intolerance
Humans who exhibit symptoms of lactose intolerance could be unable to digest A1, a protein most often found in milk from the high-producing Holstein cows favoured by American and some European industrial dairies. The A1 protein is much less prevalent in milk from Jersey, Guernsey, and most Asian and African cow breeds, where, instead, the A2 protein predominates. The difference between A1 and A2 proteins is subtle. The A2 variety of beta-casein mutated into the A1 version several thousand years ago in some European dairy herds. Two genes code for beta-casein, so modern cows can either be purely A2, A1/A2 hybrids, or purely A1. Milk from goats and humans contains only the A2 beta-casein, yet not everyone likes the flavour of goat milk, which also contains comparatively less vitamin B-12 – a nutrient essential for creating red blood cells.
Editor’s note: Another reason to promote local breeds for dairy production? Consumer adoption of dairy products in developing countries could well be determined by the content of A2 protein.
(Mother Jones, 12/03/2014)
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