CRN: RCT results don’t necessarily debunk benefits of dietary supplements

12/1/2008

WASHINGTON Results of randomized, controlled trials that don’t vet the benefits of dietary supplements as noted in prior observational trials don’t necessarily debunk those benefits, the Council for Responsible Nutrition stated in a release last week.

“Over the past several decades, a series of observational trials resulted in exciting prospects for the benefits of antioxidant vitamins and chronic disease,” stated Andrew Shao, vice president, scientific and regulatory affairs, CRN. “These encouraging results led the scientific community to conduct the recently released randomized, controlled trials, which seemed to be the next logical step. While everyone—researchers, industry and consumers—would have been thrilled to see the positive findings from observational studies confirmed, this has not been the case. This leads to more intrigue for the scientific community—to try to determine why the results from these recent RCTs are in apparent conflict with the existing body of data,” he said.

“One explanation is that … RCTs may be inherently limited in their capacity to address the unique challenges presented by nutrients and dietary interventions. Nutrients appear to work best in combination with other nutrients, yet RCTs tend to examine effects of unique chemical molecules in isolation—which is how pharmaceuticals work. Further, in using RCTs to study nutrition questions, there is the challenge of being able to create a true control or placebo group,” Shao noted. “In contrast to pharmaceuticals, it is both impossible and unethical to ensure participants in the control group are not exposed at any level to vitamins and minerals.”

Vitamins play a vital role in promoting overall general health and filling specific nutrition gaps, Shao added. And despite the results from recent studies, there is additional research that suggests antioxidant vitamins may play a role in helping to lower the risk of chronic diseases. “However, vitamin supplements are just one piece of the puzzle, which may be why we didn’t see the results we anticipated from the recent clinical trials,” he said. The other pieces of the puzzle may include pursuing an active lifestyle and practicing good nutrition.

“Perhaps we need to revise our expectations that one single healthy habit will serve as a ‘magic bullet’ and allow us to live disease-free—after all, one piece does not complete the whole puzzle, but we certainly don’t discard the piece just because it doesn’t fit in a particular spot.”

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