Similac gold 4 is designed for babies HMO (2-fl). The HMOs found in human milk support your growing child's digestive system. And because70% of the immune system exists in the gut, keeping your little one's digestive system healthy also means strengthening their immunity. HMOs serve as food for good bacteria in the gut. When beneficial bacteria are properly nourished, they are able to grow, multiply, and fight off bad bacteria. Good bacteria also produce short-chain fatty acids that strengthen the immune system further. HMOs act as decoys that prevent bad bacteria from attaching to gut cells thus, preventing them from entering your child's system. Some HMOs are also absorbed into the bloodstream where they can trigger immune cells to release protective factors, regulate allergies or infections in your child. Thus, HMOs deliver an immunity boost beyond the gut.