Junkfood Science: It will rot your teeth out!

May 10, 2007

It will rot your teeth out!

The news presented a very dim picture on the latest “Trends on Oral Health Status” report from the U.S. Centers for Disease Control and Prevention (CDC). We heard that preschoolers’ teeth are decaying as never before and they’re getting fat — and it’s all parents’ fault for giving their tots too much sugar and processed foods. It perfectly illustrates how misinformation and pop beliefs can lead us astray from effective public health policies and information that can constructively help children and families.

Associated Press headlines proclaimed:

Too much sugar putting too many cavities in baby teeth, study says

Cavities on rise in baby teeth; too much sugar, experts report

Tooth decay in young children's baby teeth is on the rise, a worrying trend that signals the preschool crowd is eating too much sugar, according to the largest government study of the nation's dental health in more than 25 years....One reason is that parents are giving their children more processed snack foods than in the past and more bottled water or other drinks instead of fluoridated tap water, [Dr. Bruce Dye of the National Center for Health Statistics] said. “They're relying more on fruit snacks, juice boxes, candy and soda (for the sustenance of preschoolers)."

And, even a dentistry news story somehow managed to tie in the “obesity epidemic:”

“The same things contributing to the obesity epidemic can also contribute to tooth decay," said Dr. Gary Rozier, a dentist who teaches public health policy at the University of North Carolina.

The Reuters version was also quick to blame sugary foods and bad parents:

Sugary foods and drinks and non-fluoridated bottled water may be helping to rot the teeth of more young U.S. children, reversing four decades of progress against tooth decay, U.S. health officials said on Monday....several likely factors, including parents serving young children more prepackaged foods with high sugar content, more sugary juices and sodas and more bottled water, much of which is not treated with fluoride....

A brief mention of positive news was near the bottom of the story, saying:

Among those aged 12 to 19, the rate fell to 59 percent from 68 percent. Dye said it is not clear why tooth decay rose among the younger children but not among the older children.

It is unimaginable why it wasn’t clear, since several pages of the CDC report were devoted to demonstrating the most likely factors, and the medical literature has consistently supported the same for decades. It is equally unbelievable that none of the reporters appear to have read the CDC report because if they had, they would have seen that sugar was never even mentioned in the 104-page report.

Not once.

Neither were processed foods, snacks, sugary juices or sodas.

The actual findings

The CDC report actually brought pretty good news: “Americans of all ages continue to experience improvements in their oral health.” Based on data from the National Center for Health Statistics NHANES surveys from 1988-1994 to 1999-2004, it said “significant decreases were found in the prevalence of tooth decay in the permanent teeth for children, teens and adults.”

According to the American Dental Association: “Findings from national epidemiologic surveys conducted since the early 1960s provide incontrovertible evidence that a dramatic decline in dental caries has occurred in school-age children in the United States.” This CDC report was no different, and reported continued improvements in children’s cavities. For permanent teeth, the prevalence of tooth decay among children and teens decreased overall. For kids 6 to 11, it went from 25% in 1988-94 to 21% in 1999-2004. Among ages 12-19, cavities dropped from 68% to 59%.

The only increases in children’s dental caries were among 2 to 5 year olds with primary (baby) teeth; for them, the average number of actual decayed and filled primary teeth went from 1.39 to 1.58.

So, what might explain why children of all ages with permanent teeth saw such improvements, while only the little ones with their baby teeth didn’t? Are we really to believe that preschoolers are consuming so much sugary foods, drinks and expensive bottled waters and they all stop after the Tooth Fairy visits?

There is a more reasoned explanation.


For a historical perspective on just how notable dental health has improved over recent decades, did you know that during the early 1970s, 90.4% of kids had dental cavities? They had an average of 6.2 cavities apiece! [To believe the sugar hypothesis, we’d have to ignore that the production of sodas and “processed foods” has risen during the years since then as cavities have plummeted. Don’t you just hate how facts get in the way of all these popular beliefs, when we stop to think about them?]

Dental caries are more than a cosmetic issue, but can result in the loss of teeth and progress to acute systemic infections. During both World Wars, dental caries and tooth loss were among the most common causes for rejection of young men from military service, according to the CDC. The public health measure that has had the greatest impact on reducing cavities in the United States and developed countries, according to the CDC, is the widespread fluoridation of water which began in selected communities in the U.S. and Canada in the 1940s. By 1992, about 56% of the population had fluoridated water. “Today, all U.S. residents are exposed to fluoride to some degree,” according to the CDC.

Recent fears surrounding fluoridated water have encouraged the growth of bottled waters, which don’t contain fluoride. So, bottled water isn't best for cavity prevention. Juices and soft drinks, and foods processed in fluoridated water, however, subsequently provide about 75% of the fluoride for some people. The safety and effectiveness of fluoride has been studied for decades. The CDC convened an expert working group to critically analyze the scientific evidence on dental caries, fluoride and public preventive health programs, which analyzed 270 papers, and it’s findings and recommendations were published in a 2001 issue of Morbidity and Mortality Weekly Report.

The Canadian Task Force on the Periodic Health Examination and the U.S. Preventive Services Task Force, as well as several expert panel reviews and the CDC’s fluoride working group have all concluded that “fluoridation of the water supply remains the single most effective, equitable and efficient means of preventing coronal and root dental caries.” These expert bodies have given fluoridation their strongest “A” recommendation has having good evidence. According to their reviews, fluoride has been shown in controlled trials to reduce caries by 20-40%.

While fluoridation of water has reduced caries population-wide and lessened disparities, disparities in dental health remain. The findings of this latest CDC report and the body of evidence offer valuable information on how we can most help from here to improve dental health among our children.

What doesn’t work

What has poor evidence for actually reducing cavities may surprise you. Despite the popularity of beliefs that sugary, “processed” foods cause cavities, dental researchers and public health experts long ago moved beyond dietary recommendations for the primary prevention of cavities among the public. When the experts reviewed the scientific evidence on sugar and carbohydrates during the development of the 2005 Dietary Guidelines for the U.S. Department Health and Human Services, they looked for every possible justification to deter us from eating these “unhealthy” foods. But the evidence on sugar promoting dental cavities came up short. Studies using the NHANES data found “no relationship between soft drink consumption and caries in individuals under age 25.” They noted that numerous studies that have looked at sugary sports drinks, soft drinks and acidic foods, and sweets, and found no relationship with cavities. The Dietary Guidelines Science Base, Section 5 on Carbohydrates, concluded that the type of carbohydrate and its retention time in the mouth has a less significant role than dental care.

The Canadian Task Force and U.S. Preventive Services Task Force, after their comprehensive reviews of the evidence, similarly concluded that dietary recommendations to reduce sugar intake has poor evidence for effectiveness and are less important for most people nowadays. Even children consuming high levels of sugary foods were found in several longitudinal studies to have low incidences of cavities. “Thus, routine dietary counselling today may be misguided. As well, the effectiveness of dental counselling in inducing behaviour change is suspect,” said doctors Donald W. Lewis, DDS, DDPH, MScD, FRCDC and Amid I. Ismail, BDS, MPH, DrPH who led the Canadian Task Force. What may be especially surprising, is that both Task Forces found there was little evidence that toothbrushing or flossing as ordinarily practiced reduce cavities, although they continue to recommend both for good hygiene and to help control gum disease.*

What is the single greatest factor in cavities today?

Social class.

Social class is two times more significant to cavities than toothbrushing, and three times more significant than any sugary consumption, according to the HHS. The scientific reviews concluded that restricting sugary foods doesn’t have nearly the impact on caries in young children as dental care. An oral health survey of 17,256 children, representing 93 percent of children residing in 62 Tennessee communities, for example, reported in the Journal of the American Dental Association a few years ago conclusively found: “Dental health was significantly worse for low-socioeconomic communities than for medium- and high-SES communities.” The CDC’s 2001 review also concluded that low socioeconomic status most determined risk for dental caries.**

According to this latest CDC report, dental caries varied significantly by poverty status. These discrepancies are similar to the last CDC report issued on August 26, 2005, which found that among children ages 2 to 11 years old, about 55% of the Mexican-American kids had cavities compared to 38% of the whites; and that over 55% of the poor children had cavities compared to 30% of the children from families with incomes greater than 200% of the poverty level.

It is simply cruel prejudice to look at a poor child and assume his/her parents are too stupid or incapable of feeding their child well or that a poor or fat child must be eating more sugar or “bad” foods than other children. As we’ve seen, even those mothers on government assistance, are following pediatricians’ recommendations for sweet drinks and juices. The HHS Dietary Guideline science review specifically cautioned that studies showing an association between sugar and cavities in children failed to note that sugary foods were simply proxies for other life situations that were much more predictive and significant in caries.

Why might poverty have such a significant role, far beyond brushing or diet?

The poor have less access to dental services and dental insurance, according to the CDC. And what is proving to have the biggest impact over recent years beyond improvements seen in water fluoridation, according to the Canadian Task Force and U.S. Preventive Services Task Force, is preventive dentistry. Professional topical fluoride applications and fluoride dentifrices for high risk people or with active decay have good evidence for effectiveness, with “A” recommendations. And one of the most important measures, which also explains the discrepancies seen in dental health among children, according to the American Dental Association, is “the percentage of children with dental sealants, [which is] directly related to the community’s socioeconomic status.” Dental sealants have been extensively studied in randomized clinical trials and have proven to be effective in reducing surface decay.

This is exactly what this new CDC report found.

This latest CDC report makes a special point of showing that tooth decay directly relates (inversely) to the use of dental sealants. Sealants are mostly placed on permanent teeth after they completely erupt beyond the gum behind the baby teeth. Sealants also go along with professional dental care. The CDC report found that from 1988 to 2004, the prevalence of dental sealants on permanent teeth among ages 6-11 increased from 22% to 30%; and among ages 12 to 19 increased from 18% to 38%.

And the report clearly shows that children receiving dental sealants and dental care is most determined by their socioeconomic situation. Among 6 to 8 year olds, only 5% of the poor children living in families under 100% of the poverty level had sealants compared to 20% among the well-off children in families over 200% of the poverty level. Among 9 to 11 year olds, half of the wealthier kids had sealants compared to less than a third of the poor ones. The poorest children also had more than three times the unfilled cavities, reflecting their general lower access to preventive dentistry care.

So, while the overall prevalence of caries has dropped among American children, it continues to be highest among the poorest children. If we are sincerely interested in helping children, we wouldn’t be condemning parents for juice boxes and fruit snacks, and spending massive resources on public programs to eliminate sugary drinks for which there is poor supportive evidence. Instead, we would be helping to improve access to preventive dentistry.

* What causes a cavity?

Cavities result from a progressive demineralization of the tooth enamel. “Demineralization” isn’t usually caused by acidic foods, and we normally eat a wide variety of acidic foods, such as fruits and vegetables, condiments and yogurts, most with more acid than in sodas. Actual dental erosion (demineralization from direct contact with acids) is relatively rare and found in those with bulimia or GERD due to continual gastric acids hitting the teeth, made worse among those with reduced saliva.

Most demineralization is caused by acids produced by bacteria in plaque that ferment with dietary carbohydrates. “Dental caries is an infectious, transmissible disease,” according to the CDC. That’s one reason caries run in families and why good dental care is important for parents in helping to reduce it among children. These acids dissolve the hard surfaces of teeth and, if unchecked, can penetrate the underlying dentin and reach the soft pulp tissue, resulting in pain, loss of the tooth and infections. Demineralization is normally balanced by natural remineralization that occurs a few hours after eating, thanks to saliva. Remineralization can also be promoted by rinsing with water after eating and brushing with a fluoride toothpaste.

Fluoride inhibits the demineralization of enamel, enhances remineralization and inhibits the activity of cariogenic bacteria. It concentrates in plaque and is in our saliva. It can slow or reverse the progression of existing lesions, according to the CDC. Brushing with a fluoride toothpaste, while modest alone in comparison to water fluoridation, can help reduce cavities by their application of fluoride, reported the CDC. And, as with anything, too much fluoride can be a problem. The Canadian Dental Hygienists Association offers a guide to fluoride safety for children here.

A food’s contribution to decay is determined by how long it’s in contact with the teeth. With tiny tots, this is one of the reasons we discourage parents from letting them suck for hours on juice bottles, but as we’ve seen, parents are doing fine in following juice recommendations. Liquids that are swallowed, however, are less a problem than carbohydrates that are chewed, sticky or kept in the mouth a long time. So many of those “healthy” chewy things like granolas, raisins and dried fruits; cooked starches and grains; and baked breads actually contribute more than drinks. Sugary foods and drinks consumed as part of meals are also less of a problem since remineralization is disrupted with meals anyway.

** Children and adults with special medical problems are at higher risk for dental caries. These include bulimics, those with Sjogren’s syndrome, and those receiving therapeutic radiation, chemotherapy, or medications that reduce salivary flow. Other things that place individuals at high risk for cavities include malformed enamel or dentin; family history for caries; exposed root surfaces; impaired ability to maintain oral hygiene; low salivary buffering capacity (saliva neutralizes acids less well); and the wearing of space maintainers, orthodontic appliances, or dental prostheses.

© 2007 Sandy Szwarc

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