Advertisement for a lactase supplement: Lactase, an enzyme produced by the body, aids in the digestion of lactose, a natural sugar found in dairy foods  Many subjects in an experiment who drank a liter of milk on an empty stomach showed signs of lactose intolerance -- difficulty in digesting dairy products because of insufficient lactase
Thus, extrapolating from the number of subjects adversely affected, at least 50 million people in North America alone should take lactase supplements
Most people who consume dairy products consume less lactose at each meal than the amount found in a liter of milk.