A 2-week-old neonate born to consanguineous parents presents with vomiting, jaundice, hepatomegaly, and failure to thrive after initiation of milk feeding. Laboratory investigations show elevated galactose-1-phosphate levels and reduced enzyme activity. Newborn screening confirms deficiency of the enzyme marked **B** in the galactose metabolism pathway diagram. Which of the following is the most appropriate long-term management for this patient?