The American Academy of Pediatrics weighed in on juice back in 2017, and the stance is still the same today: no juice before age 1. A bottle or sippy cup containing anything other than water and left in an infant’s mouth while sleeping can cause decay. This happens because sugar in the liquid mixes with bacteria in dental plaque, forming acids that attack the tooth enamel.

Effects of Sugar on Teeth

Each time a child drinks liquids containing sugar, acids attack the teeth for about 20 minutes. When awake, saliva carries away the liquid. During sleep, the saliva flow significantly decreases and liquids pool around the child’s teeth for long periods, covering the teeth in acids.