Humans have been drinking milk for centuries, yet it doesn't always sit well in our tummies. What you may not know is that you can enjoy fresh cow's milk without the discomfort. The answer lies in the a1 and a2 proteins found in milk. a1 is the culprit behind manyof the uncomfortable symptoms people experience after drinking milk. a2 Milk is the only dairy milk derived from cows that naturally produce only the a2 protein and none of the tummy-grumbling a1. a2 milk can be found in all leading supermarkets and many Australian cafes.