to the editor: This article on infant formulas was informative and well written. However, in primary lactase deficiency (the common form of chronic lactose intolerance), the actual prevalence in infants, and subsequent management, should be further discussed.

The author mentions that most proven cases of lactose intolerance develop after 12 months of age. Limited data suggest that children younger than two years do not have primary lactase deficiency,^1,2 and that the lactose intolerance present in many adults³ develops sometime after two years of age.

In adults, reports on clinical symptoms of lactose intolerance (such as diarrhea, flatulence, and abdominal pain) are prone to subjectivity.⁴ The same may be said for infants and children younger than two years, making patient counseling more difficult. Further complicating matters is that there may be drawbacks to switching to a lactose-free formula, because recent evidence indicates that lactose-free diets result in lower calcium absorption.⁴

The author mentions that many physicians suggest a trial of lactose-free formula to see if symptoms reported by the parents improve. However, there is little evidence that this practice is beneficial. Educating parents about the available data is an important part of the formula discussion, and may provide equivalent reassurance to parents as the often unnecessary (and potentially harmful) practice of switching formula.