Soda in a sippy cup?

Most parents wouldn’t dream of it. But researchers say when a baby’s bottle or cup is filled with juice — even the 100 percent, all-natural, no-sugar-added stuff — parents might as well be pouring Pepsi.

A growing body of science is linking sweet drinks, natural or otherwise, to a host of child health concerns — everything from bulging bellies to tooth decay.

“All of these beverages are largely the same. They are 100 percent sugar,” Dr. David Ludwig, an expert on pediatric obesity at Children’s Hospital Boston, said recently. “Juice is only minimally better than soda.”

The trouble is that parents who are quick to limit a child’s soft drink consumption often overlook or even encourage juice indulgence thanks to the beverage’s good-for-you image.

But that image can be overstated. Though healthy in moderation, juice essentially is water and sugar. In fact, a 12-ounce bottle of grape soda has 159 calories. The same amount of unsweetened grape juice packs 228 calories.

The $10 billion juice industry maintains that a conclusive link between its products and obesity has yet to be established, but researchers say sugar is sugar, and sweet drinks of any kind must be consumed with care.

Overuse of juice is a relatively recent phenomenon. Before the rise in popularity of soda, juice and other sweetened drinks during the latter half of the 20th century, water and milk were children’s primary beverages.

In a nation where nearly a third of children are either overweight or at risk of becoming overweight, health officials now say high-calorie beverages have little place in a young child’s diet.

Kimberly Kwitkiwski gives her twin 2-year-olds Jillian, left, and Jade a mixture of water and juice. Over the course of a day, the Hooksett, N.H., woman's children get only about 4 or 5 ounces of light juice. Evidence is mounting that sweet drinks are contributing to child health concerns.

“With the possible exception of milk, children do not need any calorie-containing beverages,” Ludwig says. “What is needed to replace fluid loss and satisfy thirst is the same beverage we’ve been drinking for millions of years, and that’s water.”

In 2001, the American Academy of Pediatrics issued guidelines saying fruit juice should not be given to children younger than 6 months, and that there is no nutritional reason to give it to them before their first birthday.

After that, juice is optional, though the group favors whole produce and urges parents to limit juice to 4 to 6 ounces a day for children up to 6 years old, and to no more than 8 to 12 ounces for older children. Experts say pudgy children should avoid juice altogether.

Despite the guidelines, 60 percent of 1-year-olds drink juice, averaging 11 1/2 ounces a day, according to 2002 USDA data. That’s up from 57 percent less than a decade before.