Dairy products can come from many animals, but most people get their dairy from cows. Cow’s milk contains the protein casein, as well as a type of sugar called lactose. In some people both of these substances can cause many issues. Humans lose the ability to digest lactose at the natural age of weaning, which is approximately from age 4-7, according to data collected worldwide. Most people will find that they cannot tolerate consuming dairy because of either intolerance to the lactose in milk, or the inability to properly digest the casein in milk. If you notice that you have any of the symptoms listed next, you might want to try ditching the dairy and see if you feel better. Many people report feeling much better after switching out the dairy products in their diet to dairy-free versions.