New Paradigm of Evidence-Based Nutrition

A Commentary on the Nutrient-Chronic Disease Relationship and the New Paradigm of Evidence-Based Nutrition

A discussion regarding the relationship between predisposition to many chronic diseases and the diet, nutritional status, and lifestyle of an individual.

Continued from Yesterday

Evidence-Based Medicine Vs. Evidence-Based Nutrition


* A PubMed search for “evidence-based medicine” resulted in 41,096 publications; the same search for “evidence-based nutrition” resulted in 37 publications. http://www.ncbi.nlm.nih.gov/sites/entrez Accessed August 10, 2010.

Figure 1. Pyramid describing the hierarchy of evidencebased medicine, the c cornerstone of which is its strong reliance on the randomized, controlled trial as the “gold standard” of evidence.

These nuances, while seemingly apparent, have been largely overlooked in the design and/or interpretation of some of the most resource-intensive, high-profile RCTs conducted in recent years. The results of these recently published trials9–13 by EBM criteria has led to conclusions that there is no evidence to support the supplemental nutrient-chronic disease relationship. But given the clear, yet under-appreciated differences between drugs and nutrients, one must ask a series of importantquestions regarding study design, the questions intended to be addressed, and the questions that were actually addressed and whether broad conclusions can be drawn from these studies to serve as the basis for recommendations (or lack thereof ). If blind application of EBM to nutrition questions is inappropriate, the scientific paradigm within which nutrients should be evaluated needs to be defined.

The Women’s Health Initiative (WHI) trial13 is a glaring example of the difficulties researchers face when conducting large-scale, long-term RCTs examining the effect of supplemental nutrients on chronic disease risk, even when adequate resources are readily available. While well intentioned, the trial (which included multiple arms: calcium and vitamin D supplementation;low-fat diet; hormone replacement therapy) suffered from a host of logistical limitations, including poor compliance, extensive use of supplemental nutrients in the placebo arm (due to ethical constraints), and other administrative difficulties associated with multicenter trials. Because the investigators found themselves caught in an ethical dilemma (WHI was initiated when awareness of the bone-protecting benefits of calcium was just becoming widespread), they could not prevent the use of calcium supplements by the placebo group. The result was a median calcium intake in the placebo group of nearly 1,100 mg/day. Thus, the hypothesis ostensibly tested in the WHI trial was not “low vs. high calcium intake” but “high vs. higher calcium intake.” The erroneous message sent from this multimillion dollar ($625 million), NIH-sponsored trial was that calcium and vitamin D supplementation is not useful for maintaining bone health in post-menopausal women, which is counter to the overwhelming majority of evidence. This has prompted some to question the value of large and expensive RCTs: “The results of the WHI add further evidence that clear answers to questions about the long-term effects of diet on risks of cancers and other major diseases may not be obtainable by large randomized intervention trials, no matter how much money is spent conducting them.”14

http://www.naturalmedicinejournal.com/article_content.asp?article=117

http://www.depsyl.com/

http://back2basicnutrition.com/

http://bionutritionalresearch.olhblogspace.com/