The goal of this research is to see if the diet fed to infants in the first year of life affects the course of their cystic fibrosis (CF) disease. At this time nobody knows if changes in the diet make any difference in how sick people with CF are, but there is some evidence that certain fats in the diet may be important for children with CF. It is the goal of this research to see if adding small amounts of these fats to an infant’s diet will help children with CF.