NEW YORK (Reuters Health) – While fluoride protects against cavities, some children may be getting too much of it via fluoridated beverages, and have the telltale white streaks on their teeth to prove it.

A study of 408 Iowa children found that more than one in three showed such signs of dental fluorosis. Their fluoride sources included different types of beverages, such as infant formula and 100 percent fruit juice.

In light of the findings, parents should “beware of the potential for the risk of fluorosis,” study author Dr. Teresa A. Marshall, an assistant professor at the University of Iowa’s College of Dentistry, told Reuters Health.

Combining the fluoride in such beverages with the fluoride in toothpaste, supplements, and other sources may, in some cases, lead to mild fluorosis, such as that seen in the current study.

“Parents should be educated as to how much toothpaste their children are using and whether (fluoride) supplements are necessary,” Marshall said.

Marshall, a registered dietitian at the college, and her team conducted the study to examine associations between dental fluorosis of the permanent incisor teeth and children’s beverage consumption during infancy and early childhood.

The 10- to 13-year-old participants were followed from birth as part of the Iowa Fluoride Study. The researchers reviewed parents’ three-day diaries of the children’s beverage consumption at 6, 9 and 12 months and every four months later up to 3 years of age. They also analyzed the fluoride concentration of well waters and various purchased drinks. The children had their teeth examined by a dentist when they were 7 to 12 years old.

The findings were presented during the annual meeting of the American Association of Dental Research.

Overall, nearly 36 percent of the children had white streaks on their teeth or other signs of mostly mild dental fluorosis. These children consumed more 100 percent juice at 16 months and less milk at 9 months than did those without fluorosis, the researchers note.

Children with fluorosis also consumed more fluoride from various beverage sources, including infant formulas at 6 and 9 months and 100 percent juice at 12, 16, and 20 months than did those without any signs of fluorosis.

Thus, “fluoride intakes from beverages during infancy and early childhood contribute to fluorosis of the permanent incisors,” the researchers conclude.

Yet, Marshall stops short of recommending that parents make specific dietary changes. She instead advises that they follow recommendations by the American Academy of Pediatrics, including limiting their child’s juice consumption to four ounces daily, and says that adults should “have (their) water tested for fluoride prior to getting supplements,” as is recommended by most dental professionals.

“There’s not one recommendation that’s blanket for everyone because there’s so many different sources of fluoride,” Marshall said.