The National Institute of Child Health and Human Development wrote in their Jan. 2006 publication "Lactose Intolerance: Information For Health Care Providers":

“Individuals vary in their degree of lactose intolerance, but even children and teenagers with primary lactose intolerance can usually consume 8 to 12 ounces (1 to 1.5 cups) of milk without experiencing symptoms.

Although the degree of lactose intolerance varies, most people with lactose intolerance do not require a completely lactose free diet. Milk and milk products should not be completely eliminated because they provide key nutrients such as calcium, vitamins A and D, riboflavin, and phosphorus.”

Jan. 2006