New Paradigm of Evidence-Based Nutrition

Continued from Yesterday

A more recent example of inappropriate application of EBM to nutrition research comes from the recent study of the effect of antioxidant supplementation on preeclampsia.17

Investigators randomized more than 10,000 women to receive 1,000 mg vitamin C and 400 IU vitamin E daily or placebo between the 9th and 16th weeks of pregnancy and concluded there was no effect of antioxidants on preeclampsia. Analysis of the findings reveals that the majority of the women enrolled in the study (80%) were using multivitamins, which could have affected their baseline nutritional status and, therefore, their response to the supplemental vitamin C and E. Furthermore, vitamin C and E status was not assessed at baseline or during the study, so one cannot know whether these women were truly in need of supplementation.

Finally, the premise of the study is that oxidative stress may induce preeclampsia.

However, oxidative stress was neither measured at baseline nor during the study, so the “oxidative stress status” of these women was not known; if they were not oxidatively stressed in the first place, it follows that the antioxidant supplements would fail to have an effect. These critical nutritional nuances were overlooked by the investigators and the publishing journal as well. Clinicians should not take the results from this RCT at face value and abandon antioxidant supplementation among this target population, but instead should determine what level of confidence they have that the data from this trial are transferable to the individual patients sitting in their offices.

This “blind faith” in RCTs without consideration of study limitations and quality should be of greater concern than it currently is. A well-designed RCT eliminates variables such as comorbid conditions, concomitant interventions, and assumes individual variability in treatment response will be randomly allocated if the trial is large enough. Conversely, a clinician must carefully consider these same variables when deciding if a particular treatment is suited for an individual patient. From the clinician’s perspective, an RCT may be the best way to determine if a treatment works; however, it reveals little about which individuals will benefit. EBM applies a hierarchy of evidence (with the RCT as the “gold” standard) to guide clinical judgment rather than using clinical judgment as a guide to evidence that is relevant to an individual patient.18 Recommendations, whether they be public health-based or practitioner-patient-based, should be developed from the totality of the available evidence, not on a single study or study design.

Continued Tomorrow

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

http://www.depsyl.com/

http://back2basicnutrition.com/

http://bionutritionalresearch.olhblogspace.com/