In infants with gastroenteritis and diarrhea, lactase deficiency may develop. Which formula would not provide benefit from soy-based formula?

• A. Lactose-free formula
• B. Hydrolyzed formula
• C. Free amino acid formula
• D. Soy-based formula

Answer: (D)

Lactase deficiency in infancy means lactose in feeds can worsen diarrhea, so the goal is to use feeds that are lactose-free. Soy-based formula is naturally lactose-free, so it directly addresses the problem of lactose intolerance and would be the option most likely to provide benefit in this scenario.

The other formulas may or may not be lactose-free depending on the product, and without confirming their lactose content, they’re not guaranteed to offer the same clear benefit as a lactose-free soy-based choice. For example, some hydrolyzed or amino acid formulas can contain lactose unless explicitly made lactose-free, and they’re often used for different indications (protein intolerance or metabolic needs) rather than solely for lactose avoidance. Therefore, in the context of preventing lactose-driven diarrhea from lactase deficiency, the soy-based option best fits the goal. Note that soy-based feeds are not appropriate for all infants (e.g., soy allergy or certain metabolic conditions), but given the scenario described, they provide the most direct benefit.