No health problems in babies have been associated with Similac Organic. But to pediatricians, there are risks in giving babies cane sugar: Sucrose can harm tooth enamel faster than other sugars; once babies get used to its sweeter taste, they might resist less sweet formulas or solid foods; and some studies suggest that they might overeat, leading to rapid weight gain in the first year, which is often a statistical predictor of childhood obesity.

Asked about these concerns, Carolyn Valek, a spokeswoman for Abbott Nutrition, the division of Abbott Laboratories that makes Similac Organic, said that sucrose had been approved by the Food and Drug Administration and was considered “safe and well established.” Ms. Valek said that Similac Organic had no more sweetener than other formulas and that prolonged contact with any kind of sugar could cause tooth decay.

In Europe, where sudden increases in childhood obesity are a pressing public health issue, sucrose-sweetened formulas will be banned by the end of 2009, except when ordered by a doctor for babies with severe allergies. The 27 countries of the European Union adopted the new rules according to the recommendations of the group’s Scientific Committee on Food, which found that sucrose provided no particular nutritional advantages, could, in rare cases, bring about a fatal metabolic disorder, and might lead to overfeeding.

The F.D.A., however, which regulates infant formula, does not specify which sugars can be used, as long as they are already classified as safe. Nor does it set the amount of sugar per serving, as it does for fats and proteins.

Still, a number of pediatricians said they were surprised by the choice of sucrose.

“I would be very concerned about this as a pediatrician,” said Dr. Benjamin Caballero, director of the Center for Human Nutrition at the Johns Hopkins Bloomberg School of Public Health and an expert in risk factors for childhood obesity. “The issue is that sweet tastes tend to encourage consumption of excessive amounts,” Dr. Caballero said. Evidence shows that babies and children will always show a preference for the sweetest food available, he said, and they will eat more of it than they would of less-sweet food.