Soy-based formulas have been clinically shown to help reduce common feeding problems such as fussiness and gas. Similac Soy Isomil has nucleotides for your baby's developing immune system and prebiotics to help support the digestive system. Our gentle soy formula features an exclusive blend of DHA, lutein, and vitamin E, important ingredients found in breast milk. DHA supports brain development, lutein supports eye development, and vitamin E is an important nutrient that supports developing cells. Similac is the #1 infant formula brand fed in hospitals. Soy-based formulas are not recommended for preterm infants.