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Clinical Nutrition Science Questions

Friday, November 02, 2018

Research into the role of nutrients in health continues to face a number of methodological challenges in the choice of study design, measurement methods, and analytic options. Reliance on randomized controlled trial (RCT) design also continues to be the evidence-based Gold Standard in disease-specific nutrient research.

Scientists have been asked for years to consider whether the RCT drug model for research is actually the most appropriate evidence-based research model for nutrients, including dietary supplements.

All physicians recognize RCTs because they are such an important piece of the drug research puzzle, but we cannot ignore all the other research; case-control and cohort studies and other epidemiological data, because these studies often indicate where further research should be focused and may prove or disprove hypotheses as well as help develop them.

Steve Mister, the president of the Council for Responsible Nutrition challenged a group of scientists in a Washington, DC, symposium some years ago with this comment, "If observational studies show a benefit which is not confirmed by a clinical trial, that does not discount the importance of the initial studies. The totality of the evidence should not be dismissed."

In an article published in Nutrition Review, Jeffery Blumberg, PhD, professor in the Friedman School of Nutrition Science and Policy at Tufts University, who participates in activities relevant to the incorporation of sound nutrition science into public health policy, suggested that with each research approach, there are inherent limitations to the use of RCTs, particularly when testing the effectiveness of preventive nutrition. 

In contrast to drugs, nutrients have beneficial effects on multiple body tissues and interact in a dynamic fashion with other nutrients found in supplements and in the diet. But most large-scale RCTs only test one or a few nutrients on complicated degenerative disease that takes decades to develop.

Dr. Blumberg further pointed out that RCTs must test a very specific and narrow question under a particular set of conditions, making it difficult to extrapolate the results to the general population. Thus diet and nutrition recommendations must still rely on the totality of available evidence, rather than exclusively on a single research approach like the RCT.

It’s important that science look at the full-spectrum of micronutrient research and evidence available, including observational studies, because they can provide a clearer picture of the benefits of supplements. 

Observational studies can often better represent typical populations. These studies have a closer relationship to how foods and supplements are used in the "real world" than in a clinical setting.

Additionally, observational studies are often the only feasible or ethical approach in cases where eliminating essential nutrients as part of the RCT study design could be detrimental to the study population. The National Eye Institute (NEI) sponsored large- scale, six- to seven-year AREDs studies are perfect examples.

The Institute of Medicine's (IOM) Dietary Reference Intakes (DRIs) always include observational studies when developing nutritional guidelines and safe upper limits of micronutrients.

Ellen Troyer, Spencer Thornton, MD, David Amess and the Biosyntrx staff



Nutrition research is a catch-22. In addition to the problems associated with using RCTs for studying nutrients, using RCTs to study prevention may be neither practical, affordable or in most cases even appropriate. 

RCTs are generally based on treatment modalities. But dietary supplements, by FDA law, are prohibited from using any type of treatment claim on their products, even if there is a vast amount of supporting science; therefore, the incentive remains limited for companies to fund nutritional therapy-oriented RCTs.