Evidence-Based Nutrition

Randomized controlled trials are considered the gold standard of scientific evidence. Half get the active treatment, half get a sugar pill—works great for evaluating new drugs, but a concern is that evidence-based medicine has made a leap from considering randomized controlled trials to be a high standard to being the only standard. Consider this review of dietary interventions for multiple sclerosis by the esteemed Cochrane Collaboration. They basically concluded that there’s not much diet can do. But what about Dr. Swank’s success in treating MS with a low saturated fat diet, the most effective treatment ever reported, published in some of the world’s most prestigious journals? Of course, they knew about his work, but the study design didn’t fit the inclusion criteria considered for the review, because it was not a controlled trial.

Demanding randomized trials makes sense for drugs, which are expensive and risky, killing off a hundred thousand Americans every year, but a healthy diet has no downsides, just good side-effects; so, we shouldn’t have to wait on randomized controlled trials to start saving people’s lives.

Consider smoking. It took more than 7,000 studies and the death of countless habitual smokers before a consensus was reached in the medical community regarding the causal link between smoking and lung cancer, and still without a single randomized controlled trial. One has to wonder, how many people are currently suffering needlessly while they wait for a randomized controlled trial to confirm the results found by other kinds of strong studies?

In fact, a famous statistician, R.A. Fisher, railed against what he called propaganda to convince the public that cigarette smoking was dangerous. Since they cannot produce evidence from randomized controlled trials: a thousand kids banned from smoking, another thousand forced to smoke at least a pack and a half a day. If that type of experiment could be done, then, there would be no difficulty. Maybe instead of smoking causing lung cancer, lung cancer causes smoking. In its earliest stages, lung cancer may cause inflammation. So, anyone suffering from chronic inflammation is going to want to smoke a cigarette to make themselves feel better, and it’s that kind of comfort that might be a real solace to anyone in the 15 years of approaching lung cancer. And, to take the poor chap’s cigarettes away from him will be rather like taking away a white stick from a blind man. It would make an already unhappy person a little more unhappy than he need be.

Fisher made invaluable contributions to the field of statistics, but his analysis of lung cancer and smoking was flawed by an unwillingness to examine the entire body of data available. His smokescreen may have been because he was a paid  consultant to the tobacco industry, but also because he was himself a smoker. Part of his resistance to seeing the association may have been rooted in his own fondness for smoking, which makes me wonder about some of the foods many nutrition researchers may be fond of as well.

A famous paper in the British Medical Journal lampooned this insistence on randomized controlled trials as the only legitimate evidence.  “Parachute use to prevent death and major trauma related to gravitational challenge: a systematic review of randomized controlled trials.” They didn’t find any. Parachutes appear to reduce the risk of injury after “gravitational challenge.” We can observe that people who fall out of planes without them tend to die a bit more than those with parachutes, but their effectiveness has not been proved with randomized controlled trials. Advocates of evidence-based medicine have criticized the adoption of interventions evaluated by using only observational data. We think that everyone might benefit if the most radical protagonists of evidence-based medicine organized and participated in a double blind, randomized, placebo controlled, trial of the parachute. In other words, individuals who insist that all interventions need to be validated by a randomized controlled trial need to come down to earth with a bump.

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.

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• G C S Smith, J P Pell. Parachute use to prevent death and major trauma related to gravitational challenge: systematic review of randomised controlled trials. BMJ. 2003 Dec 20; 327(7429): 1459–1461.
• B J Kaplan, G Giesbrecht, S Shannon, K McLeod. Evaluating treatments in health care: The instability of a one-legged stool. BMC Medical Research Methodology 2011, 11:65.
• M Farinotti, L Vacchi, S Simi, C Di Pietrantonj, L Brait, G Fillppini. Dietary interventions for multiple sclerosis. Cochrane Database Syst Rev. 2012 Dec 12;12:CD004192.
• P C Gugiu, M R Gugiu. Levels of Evidence: A Reply to Berger and Knoll. Evaluation & the Health Professions 000(00) 1-4.
• R Fisher. CIGARETTES, CANCER, AND STATISTICS. The Centennial Review of Arts & Science Vol. 2 (1958), pp. 151-166.
• J Blumberg, R P Heaney, M Huncharek, T scholl, M Stampfer, R Vieth, C M Weaver, S H Zeisel. Evidence-based criteria in the nutritional context. Nutr Rev. 2010 Aug;68(8):478-84.
• P D Stolley. When Genius Errs: R. A. Fisher and the Lung Cancer Controversy. Am. J. Epidemiol. (1991) 133 (5): 416-425.
• R A Fisher. Cancer and Smoking. Nature 182, 596 (30 August 1958).
• P C Gugiu, M R Gugiu. A critical appraisal of standard guidelines for grading levels of evidence. Eval Health Prof. 2010 Sep;33(3):233-55.

Images thanks to U.S. Department of Agriculture via Flickr.

• cancer
• chronic diseases
• Dr. Roy Swank
• industry influence
• inflammation
• lung cancer
• medications
• multiple sclerosis
• smoking
• tobacco
• weight loss