Washington — An independent review of the scientific evidence for national dietary recommendations supports an increased level of public and policy confidence in the effectiveness of fluoride in reducing tooth decay at all ages, a National Academy of Sciences panel said June 10.
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The NAS Institute of Medicine convened a panel of experts to search for patterns in diet and health research that could streamline the scientific process and bring useful recommendations and information to consumers more rapidly. The panel examined research underlying NAS dietary recommendations established in reports dating from 1989 to 2001 but did not review research conducted after this, even though the panel indicated awareness of subsequent research in some areas.

While the panel found no “pattern express train” to recommend to policymakers or the public, the report urges caution on using preliminary evidence from non-controlled studies as a basis for dietary recommendations. Policymakers and regulators should rely “heavily” on large, randomized controlled studies, the report said.

“Claims about nutrient-disease relationships are more easily made than scientifically supported,” the report said in a section addressed to consumers, policymakers and regulators. “Because the implications for public health are so important, caution is urged prior to accepting such claims without supportive evidence from appropriately designed, typically large, clinical trials.”

The committee increased the confidence rating scale for just three of the 14 diet-health relationships reviewed, reporting an increased level of confidence in the scientific evidence for the fluoride-dental caries relationship over the decade between relevant NAS dietary reports. This was the only diet-health relationship for which the panel increased the level of confidence from “accepted” to “accepted plus,” based on the extension of fluoride’s benefits from children to a broader population embracing adults.

Research provides “conclusive evidence that fluoridation of the water supply or supplemental fluoride reduces dental caries, and the (1989 NAS) diet and health report stated that ‘of all dietary components exhibiting a protective effect against caries, the most effective is fluoride’,” the committee said.

The confidence level for a relationship between vitamin C and the common cold, among the other diet-health relationships selected for review, remains “uncertain,”according to the Committee on Examination of the Evolving Science for Dietary Supplements. The committee reduced the confidence level for benefits from three dietary supplements and various cancers and left others unchanged or described as accepted and promising in one NAS report but not the other.

The committee review, Evolution of Evidence for Selected Nutrient and Disease Relationships, describes how the evidence base underpinning selected nutrient-disease relationships has changed over the past decade. The report is available to read online at the National Academy Press Web site.

The committee found that public confidence in nutrient-disease relationships can change over time and that preliminary evidence supporting a relationship is “often not confirmed.” The panel used a scale of “accepted,” “promising,” “uncertain” or “no relationship” to describe the extent to which subsequent scientific evidence agreed with or modified the evidence used to support NAS dietary recommendations.

“The analysis was also to include characteristics of information useful to consumers regarding the health effects of such food components or nutrients that allow them to make scientifically informed judgments regarding the role that a specific food component or nutrient plays in health,” the report said. The committee undertook the study at the request of the U.S. Food and Drug Administration.

Large, retrospective and intervention studies conducted before the 1989 NAS/ National Research Council report, Diet and Health: Implications for Chronic Disease Risk, provided conclusive evidence that fluoridated water and dietary fluoride supplements reduce dental caries, the committee said.

“The science in this area had already evolved to the point that the level of fluoride required to reduce caries, but not result in fluorosis, was established,” the new report said. “Additional studies conducted after the D&H report and considered in the (1997) Dietary Reference Intake report provided evidence that fluoridated water, dietary supplements, and topical application of fluoride reduce dental caries at all ages.”

Studies conducted after the 1989 NAS report on diet and health led to the conclusion that there is no evidence to support the need for additional fluoride during pregnancy, the committee said.

The seven-member committee appointed to review selected case studies of diet and health relationships and the evolving science brought expertise in nutritional epidemiology, evidence-based medicine, research design methodology, clinical medicine, dietetics and nutritional sciences. Norman Krinsky, Ph.D., committee chair, is professor emeritus, Department of Biochemistry, Tufts University School of Medicine.

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