Dr. Greene’s Answer: Normally, when someone swallows, the food
travels down the esophagus, a sphincter at the lower end
relaxes, and the food is permitted to enter the stomach, where a
pool of acid awaits to continue digesting it. The sphincter then
closes tight. When the sphincter does not remain tightly closed,
the acid and the food slosh back up into the esophagus. This is
what is meant by reflux. These refluxed stomach contents can
burn the lining of the esophagus and irritate the lungs. A small
amount of reflux immediately following meals is common in
healthy adults and causes no problems. Swallowing saliva to wash
away the acid protects the vulnerable walls of the esophagus. In
most newborns, the lower esophageal sphincter is relatively lax.
Thus, frequent spitting up is common in infants. This is called
physiologic reflux. Over time, the lower esophageal sphincter
becomes more competent; children eat more solid food; they
assume a more upright posture. The spitting up diminishes. In
most cases the spit