We definitely don’t recommend drinking the skim, pasteurized milk you find in plastic containers at the grocery store (in fact, we generally like to avoid anything that comes in a plastic container). If you can find raw, whole milk, that’s the best, but there are still some issues with it.
First off, many people can’t digest lactose or casein, and if you can’t digest something, obviously you should avoid consuming it. Even those who don’t have stomach issues sometimes notice that dairy causes other health problems for them, including mood swings, acne, and nasal congestion. As always, it’s an N=1 experiment. If you like drinking milk and it doesn’t cause any issues for you, then you should go for it.
The Nutritional Content of Milk
Whole milk is preferable to the low-fat or skim varieties because consuming fat with carbohydrates helps prevent a spike in blood sugar. Milk is also full of fat-soluble vitamins, such as vitamins A, D, E, and K, which our bodies cannot use without the fat to help transport them.
Paleo and Carbohydrates
Despite all this, milk is still pretty high in carbohydrates, with lactose sometimes contributing as much as 40% of calories from whole milk. Because of the high sugar content, if you do choose to include milk as part of your Paleo lifestyle, we recommend keeping it to an occasional treat, rather than a daily habit.
Chris Kresser has a whole post on the benefits of raw milk over pasteurized.