Soy-based formulas have been clinically shown to help reduce common feeding problems such as fussiness and gas when switching from milk-based formula. 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 premature infants with birth weights less than 1800 g.