I remember hearing it in my physiology class of med school. No citation or anything so not 100% confident but the link below seems to indicate that those with lactose intolerance may tolerate goats milk better, though it lacks a mechanistic explanation.
Originally Posted by veryhrm
Cow milk comes with lactase but it gets destroyed by pasteurization. Whether or not it is useful in your stomach if you drink raw milk is debatable.
Originally Posted by vanslix
This is a really common misconception and I dont know how it started. There are a lot of enzymes in milk, and a lot of them are killed by pasteurizing it , but there isnt lactase in there.
Originally Posted by Caje
Lactase is produced in the small intestine as a digestive enzyme, it cant make its way from the intestine into the mammary glands and into milk.
If lactase WAS in milk, it would be breaking down the lactose presumably while its still in the mammary gland, rendering the whole thing basically useless. Milk would be digesting itself. But if milk HAD the means to digest it already, there would be no need to produce lactase in the intestines at all.
Post-weening lactose intolerance is a natural state, it is only through a genetic mutation that lactase production continues through adulthood in some populations. Such an adaptation would not have been advantageous, and would not have spread, if (during the thousands of years before pasteurization) there was enough lactase in raw milk for it to be already digestible.
No milk, be it goat, cow, human, or bengal tiger is any different in this respect. There are differences in how easily milk from different animals (and i imagine in different states e.g. raw vs. processed) is absorbed in the body. They have a different fatty acid composition, which affects how efficiently its broken down. Because goat milk is processed faster, theres basically less time for it to cause problems in the digestive system, making the discomfort far less acute for most people with a lactose intolerance.