Lactose Intolerance After WLS

Lactose, the natural sugar found in milk products, is digested in the small bowel by means of the enzyme lactase. About 10% of adults in the United States are lactose intolerant. They do not have enough lactase to digest milk. When they eat milk or milk products, they develop crampy abdominal pain, bloating and diarrhea. Lactose intolerance can be acquired after gastric bypass or other gastric surgeries by as many as 10% of patients. When a person with a normal stomach drinks milk, it accumulates in the stomach and then is released slowly into the small intestine. There is enough lactase available to handle a small amount of milk at a time. After gastric bypass, milk passes directly through the gastric pouch into the small bowel at a much higher rate. The milk overwhelms the available enzyme and the lactose intolerance symptoms occur.

The strategies to deal with lactose intolerance that develops after surgery are to take milk products more slowly, eat thicker products such as yogurt or cheese rather than liquids milk, avoid milk products all together, or take an enzyme substitute Lactaid with meals.
The following information on the lactose-controlled diet and use of lactaid was provided by Marylyn Swift, RD from a hospital dietary manual.