"Juice and soda essentially contain the same carbohydrates, so the body reacts to them the same way," Lustig explains. "Juice contains fructose, glucose and sucrose, while soda contains high-fructose corn syrup, which is 55 percent fructose and 45 percent glucose."
He adds that juice is actually worse than soda because juice has a higher energy density or more calories per ounce. While most sodas have 150 calories in a 12-ounce serving, juices have about 170 calories for the same amount.
"People incorrectly think juice is natural and healthy simply because it's extracted from fruit. But there's nothing natural about extracting juice from fruit," says Lustig. "It's the fruit in its entirety that's good for you. The human body needs the fiber, which is what holds the fruit together. The fiber is the good part of the fruit and the juice is the bad part of the fruit. The juice is nature's way of getting you to eat your fiber."
UCSF Medical Update - Drinking juice is no better than drinking [regular] soda