LACTASE DEFICIENCY - An intolerance to milk and dairy products due to a deficiency of lactase in the intestine. Lactase is a enzyme which breaks down milk sugar, or lactose. This condition is common in adults and may affect as many as 70-90% of Asians, African Americans, Native Americans, and Mediterranean populations. This condition may also develop as the result of an intestinal disease such as celiac sprue. Symptoms include abdominal cramps, bloating, nausea, weight loss, and diarrhea. Treatment involves removing milk products from the diet. For infant's see Lactofree or ProSobee.