According to an article from Reader's Digest, there is new evidence that shows how harmful drinking lots of fruit juice can be for children younger than 24 months. The liquid fills their tiny stomachs and ruins their appetite for foods with needed nutrients and calories. A study published in Pediatrics indicated the resulting malnutrition can prevent babies from developing normally.

Eight children, ages 14 months to 27 months, whose growth had lagged behind their peers, were examined at Maimonides Medical Center in New York. Each was drinking 12 to 30 ounces of juice a day. After recording what else the children ate, researchers realized the fruit beverages accounted for 25 to 60 percent of the daily calorie consumption. Soon after the parents gave their children less juice and more milk, the infants gained weight.

Health professionals suggest babies under six months shouldn't be given juice; some pediatricians suggest waiting until after the first birthday. Whenever they start, young children shouldn't have more than a few ounces a day. Since apple juice contains two sugars that tots can't absorb, large amounts can cause diarrhea.