Is a soy formula recommended in infants with acute diarrhea associated with gastroenteritis who develop secondary lactase deficiency?

• A. Yes
• B. No
• C. Only with lactose-containing formula
• D. Only after antibiotics

Answer: (B)

Secondary lactase deficiency from gastroenteritis means the gut can’t digest lactose well, so giving lactose-containing feeds worsens diarrhea. The goal is a diet that minimizes lactose while still providing adequate calories and fluids, which is best achieved with lactose-free feeds. Soy-based formulas are not recommended in this acute setting because, despite being lactose-free, they carry other nutritional and safety concerns for infants and there isn’t clear evidence they’re the preferred option during acute gastroenteritis. The usual approach is to use a lactose-free cow’s milk–based formula or continue breast milk if possible, ensuring proper hydration and nutrition.