Nutrition Science Evidence
November 19, 2010
All scientists 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, as these studies often indicate where further research should be focused and they may prove or disprove hypotheses as well as develop them.
Steve Mister, the president of the Council for Responsible Nutrition challenged a group of scientists in a Washington, D.C. symposium 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 August 2010 article in Nutrition Review Jeffery Blumberg, PhD, professor in the Friedman School of Nutrition Science and Policy at Tufts University 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 the diet. But most RCTs can test only one or two compounds, each at a single dose, for a few years. This is too short a period to have significant impact on chronic 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 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 it 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 Institute of Medicine's (IOM) Dietary Reference Intakes (DRIs) include observational studies when developing nutritional guidelines and safe upper limits of micronutrients.
Ellen Troyer, MT MA -
Biosyntrx CEO / Chief Research Officer
Double Ended Spatula 6-105-1
Evidence-based criteria in the nutritional context. Blumberg J, Heaney PR. et al. Nutr Rev. 2010 Aug,68(8):478-84 [abstract]