There are many common misconceptions regarding milk, digestion, intolerances and allergies. Your body uses digestive enzymes in the stomach and intestine to help you digest milk protein; supplemental enzymes or other dietary supplements don't have any additional effect. Furthermore, you don't need additional help digesting milk protein; it's not possible to have a specific problem with milk protein digestion.
The process of digestion -- breaking down the large nutrient molecules in the food you eat into smaller molecules -- depends on water, acid and digestive enzymes. Different digestive enzymes help with the digestion of different nutrient compounds. For instance, you use enzymes called amylases to break down starch, while enzymes called lipases break down fat. Milk proteins -- and all other dietary proteins -- are broken down by protease enzymes.
You secrete protease enzymes from cells in the lining of your stomach and also from your pancreas, says Dr. Lauralee Sherwood in her book "Human Physiology." Stomach cells secrete proteases into the stomach itself, while the pancreas secretes its digestive enzymes into the small intestine. While enzymes are specific with regard to what kinds of molecules they digest, proteases can't differentiate between milk proteins and other dietary proteins. You don't have specific milk protein-digesting enzymes.
Allergies and Intolerances
Some people have milk intolerance, while others have true milk allergies. Intolerance is due to an inability to digest the sugars -- not the proteins -- in milk, and you can benefit from supplemental enzymes. A milk allergy results from your immune system reacting to the proteins in milk as invading organisms, with far more serious symptoms than those associated with an intolerance, according to MayoClinic.com. An allergy, however, has nothing to do with inability to digest milk.
If you think you're having trouble digesting milk, it may be that you aren't tolerant of -- meaning able to digest -- milk sugar, or lactose. If your symptoms are more severe, you could have an allergy. Either way, see a doctor to help you determine the source of the problem. Because you can digest milk protein if you can digest other proteins, you don't need supplements to help you do so -- and such supplements won't have an effect on your ability to process milk.