Designed by a doctor in 1996, Dr. Brown’s Natural Flow® is the only baby bottle to feature an internal vent system that is clinically proven to reduce colic. Dr. Brown’s bottles also help reduce spit-up, burping and gas by eliminating negative pressure and air bubbles, help preserve vitamins C, A, & E by minimizing oxidation of breastmilk and formula, and provide vacuum-free feeding similar to breastfeeding
From.https://www.drbrownsbaby.com Dr.Brown's
Designed by a doctor in 1996, Dr. Brown’s Natural Flow® is the only baby bottle to feature an internal vent system that is clinically proven to reduce colic. Dr. Brown’s bottles also help reduce spit-up, burping and gas by eliminating negative pressure and air bubbles, help preserve vitamins C, A, & E by minimizing oxidation of breastmilk and formula, and provide vacuum-free feeding similar to breastfeeding
From.https://www.drbrownsbaby.com