And people naturally like dairy foods. They taste good and are fat-rich with a high satiety value. Dairy makes you feel full for a long time. Dairy is also high in protein; protein is hard to digest and this too keeps one feeling full for a long time. But many people, especially those from cultures who traditionally (genetically) didn't have dairy cows, particularly Africans, Asians and Jews, just do not produce the enzymes necessary to digest cows milk. Some individuals belonging to these groups can digest goats milk. Some can't digest any kind except human breast milk. And some can digest fermented milk products like yogurt and kiefer. Whenever one eats a protein food that is not fully digestible, it putrefies in the digestive tract, with all the bad consequences previously described. But no one, absolutely no one can fully digest pasteurized cows milk, which is what most people use because they have been made to fear cow-transmitted diseases and/or they are forced to use pasteurized dairy products by health authorities. I suspect drinking pasteurized milk or eating cheese made from pasteurized milk is one of the reasons so many people develop allergic reactions to milk. Yet many states do not allow unpasteurized dairy to be sold, even privately between neighbors. To explain all this, I first have to explain a bit more about protein digestion in general and then talk about allergies and how they can be created. Proteins are long, complex molecules, intricate chains whose individual links are amino acids. Proteins are the very stuff of life. All living protoplasm, animal or plant, is largely composed of proteins. There are virtually an infinite number of different proteins but all are composed of the same few dozen amino acids hooked together in highly variable patterns. Amino acids themselves are highly complex organic molecules too. The human body custom-assembles all its proteins from amino acids derived from digesting protein foods, and can also manufacture small quantities of certain of its own amino acids to order, but there are eight amino acids it cannot make and these are for that reason called essential amino acids. Essential amino acids must be contained in the food we eat. . Few proteins are water soluble. When we eat proteins the digestive apparatus must first break them down into their water-soluble components, amino acids, so these can pass into the blood and then be reassembled into the various proteins the body uses. The body has an interesting mechanism to digest proteins; it uses enzymes. An enzyme is like the key for a lock. It is a complex molecule that latches to a protein molecule and then breaks it apart into amino acids. Then the enzyme finds yet another protein molecule to free. Enzymes are efficient, reusable many many times.