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Release: Feb. 24, 2000

Fluoride in soft drinks could lead to fluorosis, UI study says

IOWA CITY, Iowa -- The presence of fluoride in foods and beverages, particularly soft drinks, could be an important part of total fluoride intake for young children and should be considered by physicians and dentists when thinking about prescribing fluoride supplements, according to University of Iowa College of Dentistry researchers.

Dental fluorosis is a condition resulting from exposure to excessive amounts of ingested fluoride while teeth develop in early childhood. Judy Heilman, research assistant in the Dows Institute for Dental Research in the UI College of Dentistry, said the majority of soft drinks have substantial concentrations of fluoride that may be an important part of total fluoride ingestion, possibly contributing to fluorosis.

"Few studies have reported fluoride levels in soft drinks and since there is an increase in carbonated beverage consumption among children, they may be receiving substantial fluoride intake from soft drinks," she said. "This added amount of fluoride needs to be considered when dentists are making the decision to recommend fluoride supplements."

Dental fluorosis does not appear until years after exposure to excessive fluoride, after the teeth come into the mouth. It appears as dull, chalky, mottled enamel on the child's permanent teeth, and in severe cases orange or brown stains may occur. According to Heilman, recent studies have reported that the prevalence of dental fluorosis has increased significantly in the United States and Canada, by as much as 20 to 70 percent.

In a study led by Heilman and published in the November 1999 issue of the Journal of the American Dental Association, researchers tested more than 300 carbonated beverages purchased in eastern Iowa for fluoride concentrations. Fluoride amounts ranged between .02 to 1.28 parts per million (ppm). Optimal fluoride levels in water are .7 to 1.2 ppm. More than 70 percent of the soft drinks contained more than .60 ppm. The most important determinant in fluoride content for these drinks was their production site and the fluoride levels in the water used in making the soft drinks.

Other studies have found increasing rates of soft drink consumption among children, Heilman said. In one national study 39 percent of the children drank up to 8.9 ounces of carbonated beverages a day, while 12 percent drank 9 or more ounces. The consumption of one 12-ounce can of a soft drink may account for a considerable portion of a child's daily beverage intake, Heilman said, making the fluoride concentration in these drinks extremely important.

Besides soft drinks, Heilman said fluoride is found in other beverages and food products.

"It's important to realize that carbonated beverages are only one of several sources of possible ingested fluoride," she said. "We have already conducted tests on juice, juice drinks, infant formulas, milk, cereals and baby foods and we've found a wide range of fluoride levels. The majority of the fluoride here is coming from the water source at the production sites."

The fluoridation of public water supplies has contributed significantly to the decline of tooth decay, a major public health problem through most of the last century, said Steven Levy, D.D.S., professor in the College of Dentistry and co-author of the study. However, the greater variety of sources of fluoride now creates a much more complex situation.

"Most children today have much lower rates of tooth decay and no missing teeth, largely due to water fluoridation," he said. "The Centers for Disease Control recently recognized fluoridation of public water supplies as one of the 10 great public health achievements of the 20th century. However, now there are more varied sources of fluoride ingested by more young children, which accounts for the data on increased frequency of mostly mild fluorosis."

About 4 percent of the U.S. population consumes drinking water with naturally occurring optimal fluoride levels and about 52 percent consumes drinking water with added fluoride, Heilman said. In areas where the water is not fluoridated, however, it would seem that soft drinks and other products could provide some fluoride that residents would otherwise not receive. The researchers realize this can cause a problem.

"Since fluoride is present in rinses and water-based products that come in from other areas, there really are no non-fluoridated areas," she said. "If a community has water without added fluoride, an assumption often is made that the child is not getting enough fluoride. Although this may be true from the drinking water alone, other sources need to be considered."

When prescribing fluoride supplements, physicians and dentists should think not only of home water as a fluoride source, but also substantial quantities of soft drinks and juices, Heilman said. Assessing these fluoride sources is a tough task, but some sort of labeling could be the key.

"Companies would have to be willing to undertake the venture of labeling," Heilman said. "They would have to have the finished products or the water used in production measured for fluoride on a regular basis as levels can vary. This could help in tracking the total dietary fluoride intake and help physicians and dentists decide whether to recommend fluoride supplements."

Although many soft drinks have fluoride, parents should not replace their kids' glasses of milk, juice or water with their favorite soft drinks to give their child more fluoride, she said.

"Soft drinks have a lot of sugar and acidity and lack important nutrients. Consuming them is not conducive to oral health, so they should be taken in moderation."

Other UI College of Dentistry collaborators on the study include Mary Kiritsy, research assistant in preventive and community dentistry and James Wefel, Ph.D., professor of pediatric dentistry and director of the Dows Institute for Dental Research.