Q: Just how bad is it to give kids fruit juice before they turn 1?

A: Fruit juice has been touted as "part of a nutritious breakfast" for years. As a child, I was told that juice was good for me, providing me with vitamin C. After all, it was a healthier alternative to sodas, and it tasted good. Today, kids routinely drink cranberry juice, orange juice, grape juice, apple juice and many other juices for those reasons. But now, with the epidemic of obesity and diabetes, adults are starting to think more carefully about the sugar content of fruit juice.

Fruit juice contains four sugars: sucrose, glucose, fructose and sorbitol. All of these, except sorbitol, are easily absorbed by the body and raise blood sugar and insulin levels. In addition, the sugars from juice that are not absorbed can cause bloating, abdominal pain and diarrhea in toddlers.

Another problem with fruit juice is that you easily get all the sugar of a fruit, but without the fiber. Take orange juice, for example. If you were to eat an orange, your hunger might be satiated enough not to eat another, thus limiting your sugar and caloric intake. However, an 8-ounce glass of orange juice might require four oranges. This is true for many other fruits as well. That's a lot of sugar and calories, with all their negative effects.

A recent policy statement from the American Academy of Pediatrics suggests that infants who drink fruit juice may be less likely to eat fruits when they are older, and, further, infants might be replacing milk with juice. Milk, in addition to sugar, has a substantial amount of the protein, fat and vitamins necessary for growth. However, juice has sugar and some vitamins, but no protein or fat. Not convinced? Excessive consumption of juice in children has been associated with malnutrition and short stature. (Note that because water lacks nutrients, it's not recommended for infants younger than 6 months.)

Another worry about the sugar in fruit juice is the effect it has on young teeth, because prolonged exposure to sugar leads to cavities. The risk is heightened when infants are given juice in a bottle or sippy cup, because they can carry the bottle or sippy cup with them -- drinking whenever they want. Both the American Academy of Pediatrics and the American Academy of Pediatric Dentistry recommend that juice be given only in an open cup to minimize how much a child drinks.

I agree that giving juice to children younger than 1 year of age is not healthy for them. But the same holds true for those older than 1. Juice may have some health benefits, but overconsumption will still ultimately lead to a greater risk for obesity, cavities and diabetes. So parents of older children should continue to control their consumption of juice. And, because they're not reliant on liquids for nutrition, teaching them to use water to slake their thirst is a good idea.

We've focused here on drinks that are 100 percent juice. The unhealthy elements of juice become even more pronounced when sugar is added to create a "fruit drink" or a "juice cocktail."

I understand that it's hard for a parent to say no to a crying infant who craves juice or a fruit drink. But doing so is much easier than trying to change entrenched unhealthy habits.

Robert Ashley, M.D., is an internist and assistant professor of medicine at the University of California, Los Angeles. Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.