Many people run into stomach woes when they eat dairy because they lack lactase, the enzyme that digests the milk sugar lactose. If that sounds like you, it’s possible for your intestinal bacteria to develop the lactase that your intestines themselves can’t make. To see if the training will work for you, start by drinking just a little bit of milk every day, then slowly increase the amount. In some cases it may only take a couple of weeks to regain the ability to digest dairy.

READ MORE: Why You Should Be Wary About Dairy