Several scholars from the International and American Association for Dental Research (IADR/AADR) are calling for a re-emphasis on free sugars as the main cause for caries. The authors of two recent papers criticize both the thought that caries is a "multifactorial condition" and the lack of sugar-related policies.
The first article, "Diet and Dental Caries: The Pivotal Role of Free Sugars Reemphasized," reviews various clinical studies and argues that free sugars are the primary factor in the development of caries. The second, "The Confluence of Sugar, Dental Caries, and Health Policy," examines how current health policies do not reflect the latest scientific research and questions what can be done to change that. Both papers were first published online in the Journal of Dental Research on August 10, 2015, and will appear in the October 2015 print issue.
"The importance of sugars as a cause of caries is underemphasized and not prominent in preventive strategies," wrote the authors of the "Diet and Dental Caries" article. "This is despite overwhelming evidence of its unique role in causing a worldwide caries epidemic."
Aubrey Sheiham, BDS, PhD, and his co-author argued that free sugars are the primary determinant for caries, while other factors merely alter the effects. Dr. Sheiham is an emeritus professor of epidemiology and public health at the University College London.
They used the World Health Organization (WHO) definition of free sugars: "all monosaccharides and disaccharides added to foods by the manufacturer, cook, or consumer, plus the sugars naturally present in honey, syrups, and fruit juices."
This is a notable distinction, according to the authors, because the term sugar is generally used to indicate all dietary sugar; the general term does not differentiate between sugar that is added to food and sugar that occurs naturally. Instead, free sugars include all types of sugar, including those added by manufacturers and those found in natural fruit juices and syrups.
Most of the so-called caries-causing factors, which include oral microorganisms, acid, salivary flow, and the role of fluoride, are part of the disease process but are not causal factors, Dr. Sheiham and colleague wrote. By calling caries a multifactorial disease, it is misleading, because without sugars, the disease does not occur, they argued.
"So, it is clear that sugars start the process and set off a causal chain; the only crucial factor that determines the caries process in practice is sugars," the authors wrote. "Thus, to stress the multifactorial effects on the sugars-induced causal process muddies our understanding and misdirects policy."
To back up their claim, they drew evidence from research, including a study on people with a hereditary fructose intolerance, population studies before and after average sugars intake spiked, and systematic reviews. Such evidence showed that despite interventions, caries steadily progresses with age, its effects are lifelong, and there is a causal relationship between free sugars and dental caries.
"So why call caries an infectious transmissible disease when the presence of these microorganisms in the mouth is ubiquitous," he asked, "and it is only the addition of sugars that then stimulates their proliferation and adhesive qualities and allows them to produce the acids required for dental caries?"
While the authors did present substantive scientific evidence, they noted that it can be incredibly difficult to get quality research, because it is difficult to undertake "single-blind, let alone double-blind, community-based randomized trials of sucrose reduction over sufficient periods to monitor dental caries development." Furthermore, Beau Meyer, DDS, and Jessica Y. Lee, DDS, MPH, PhD, authors of "The Confluence of Sugar, Dental Caries, and Health Policy," noted that research to elicit behavior change is perhaps more difficult to undertake.
In addition, there is interference from the sugar industry, which defends itself by continuously denying that sugars are harmful, according to Dr. Sheiham and colleague. The industry also has considerable influence on international committees and organizations.
What can be done about creating new policies?
Current policies focus on fluoride, despite a growing body of evidence that sugar intake is positively associated with dental caries, according to Drs. Meyer and Lee. As a result, they essentially called for a shift from focusing on tertiary preventions, such as fluoride, to attacking the root cause -- sugars.
Dr. Meyer is a pediatric dental resident and Master of Public Health student at the University of North Carolina at Chapel Hill (UNC) School of Dentistry, and Dr. Lee is a professor and also the chair and director of research for the pediatric dentistry department at the UNC dental school, as well as an associate professor of health policy and management at the UNC Gillings School of Global Public Health.
Some policy progress has been made with the WHO's recent recommendations, which the authors of both papers mentioned. The guidelines strongly recommend limiting free sugars intake to less than 10% of total energy intake and conditionally recommend further reducing free sugars intake to less than 5% of total energy intake.
"The recommendations developed by WHO are in place to protect the health of populations while understanding that individual differences may exist," the authors wrote. "The WHO recommendations are by no means calling for a zero-tolerance policy on sugar intake; rather, they are simply calling for a reduction in sugar intake that could improve the health of populations."
In addition, the U.S. Department of Agriculture and the Department of Health and Human Services are currently drafting the nation's new dietary guidelines, which include a reduction in added sugar intake to no more than 10% of daily energy and supports labeling and educational approaches. These guidelines will be released later in 2015.
Drs. Meyer and Lee noted that more can be done, especially for addressing the accessibility of sugary products and introducing disincentives for the behavior. They encouraged policymakers to "be courageous enough to develop policies restricting sugar intake consistent with national and WHO guidelines."
Finally, the authors asked the scientific community to have a voice. They wrote that researchers understandably see a need to remain objective; however, they also need to readily communicate findings to those who can make evidence-based changes.
"There has been increasing attention on how to reduce the research, evidence-practice, and policy gaps," Drs. Meyer and Lee concluded. "This requires engagement of stakeholders who are in the appropriate positions to use the evidence to make informed policy decisions to improve the health of a population."