9 out of 10 healthcare professionals recommend Dr Brown's Natural Flow Bottle for Colic relief. The patented internal vent system creates a vacuum-free environment which eliminates the vacuum and air bubbles found in most baby bottles making feeding with this bottle closer to breastfeeding. It allows air to enter through the teat collar, without being incorporated into the breast milk or formula. The air is then channelled through the internal vent, to the area behind the feed. Over half of those changing to a Dr Brown's Natural Flow baby bottle saw an improvement in 3 feeds or less, outperforming any other brand. - Results of HCP Colic Survey carried out by Consumer Analysis Ltd - May 2010 The design of the Natural Flow Options Bottle will help to reduce colic, while the vent system eliminates the negative pressure and air bubbles which also reduce burping and wind by creating a paced flow. These BPA-free bottles can be used with or without the vent system, and helps preserve vitamins, reduce feeding problems, and aid digestion.