Does your stomach churn after you drink milk? Do you have diarrhea soon afterward? If so, you may be lactose intolerant.
The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) estimates that 30 to 50 million Americans are lactose intolerant.
Being lactose intolerant means you can’t digest lactose—the natural sugar found in milk and other dairy products. People who cannot digest lactose have a shortage, or deficiency, of an enzyme called lactase, which is produced in the small intestine. Lactase breaks down milk sugar into two simpler forms of sugar, which are then absorbed into the bloodstream.
Read more including how to avoid problems with lactose intolerance at the FDA Lactose Intolerance page