Evidence-Based Nutrition

Evidence-Based Medicine or Evidence-Biased?

Image Credit: clement127 / Flickr. This image has been modified.

Dr. Esselstyn’s landmark study, demonstrating that even advanced triple vessel coronary artery disease could be reversed with a plant-based diet, has been criticized for being such a small study. But the reason we’re used to seeing large studies is that they typically show such small effects. Drug manufacturers may need to study 7,000 people in order to show a barely statistically significant 15% drop in ischemic events in a subsample of patients. Esselstyn achieved a 100% drop in those who stuck to his diet, all the more compelling considering that those 18 participants had experienced 49 coronary events (like heart attacks) in the eight years before they went on the diet. These patients were the sickest of the sick, most of whom having already failed surgical intervention. When the effects are so dramatic, how many people do you need?

Before 1885, a symptomatic rabies infection was a death sentence, until little Joseph Meister became the first to receive Pasteur’s experimental rabies vaccine. The results of this and one other case were so dramatic compared with previous experience that the new treatment was accepted with a sample size of two. That is, the results were so compelling that no randomized controlled trial was necessary. Having been infected by a rabid dog, would you be willing to participate in a randomized controlled trial, when being in the control group had a certainty of a ‘‘most awful death’’? Sadly, such a question is not entirely rhetorical.

In the 1970’s, a revolutionary treatment for babies with immature lungs called “extracorporeal membranous oxygenation” (ECMO), transformed immature lung mortality from 80% dead to 80% alive nearly overnight. The standard therapy caused damage to infants’ lungs and was a major cause of morbidity and mortality in infants. ECMO is much gentler on babies’ lungs, “providing life support while allowing the lungs to ‘rest.’”

Despite their dramatic success, the researchers who developed ECMO felt forced to perform a randomized controlled trial. They didn’t want to; they knew they’d be condemning babies to death. They felt compelled to perform such a trial because their claim that ECMO worked would, they judged, carry little weight amongst their medical colleagues unless supported by a randomized controlled trial. Therefore, at Harvard’s Children’s Hospital, 39 infants were randomized to either get ECMO or conventional medical therapy. The researchers decided ahead of time to stop the trial after the 4th death so as not to kill too many babies. And that’s what they did. The study was halted after the fourth conventional medical therapy death, at which point nine out of nine ECMO babies had survived. Imagine being the parent to one of those four children.

Similarly, imagine being the child of a parent who died from conventional medical or surgical therapy for heart disease.

In her paper “How evidence-based medicine biases physicians against nutrition,” Laurie Endicott Thomas reminds us that medical students in the United States are taught very little about nutrition (See Evidence-Based Medicine or Evidence-Biased?). Worse yet, according to Thomas, their training actually biases them against the studies that show the power of dietary approaches to managing disease by encouraging them to ignore any information that does not come from a double-blind, randomized controlled trial. Yet, humans cannot be blinded to a dietary intervention—we tend to notice what we’re eating—and, as a result, physicians are biased in favor of drug treatments and against dietary interventions for the management of chronic disease.

Evidence-based medicine is a good thing. However, Thomas points out that the medical profession may be focusing too much on one type of evidence to the exclusion of all others. Unfortunately, this approach can easily degenerate into “ignoring-most-of-the-truly-important-evidence” based medicine.

Heart disease is a perfect example. On healthy enough plant based diets, our number one cause of death may simply cease to exist. The Cornell-Oxford-China Study showed that even small amounts of animal-based food were associated with a small, but measurable increase in the risk of some chronic diseases. In other words, “the causal relationship between dietary patterns and coronary artery disease was already well established before Dean Ornish and Caldwell Esselstyn undertook their clinical studies.” The value of their studies was not so much in providing evidence that such a dietary change would be effective, but in showing that “physicians can persuade their patients to make such changes,” and in “providing interesting data on the speed and magnitude of the change in severe atherosclerotic lesions as a result of dietary therapy.”

Therefore, any complaints that these studies were small or unblinded are simply irrelevant. Because the evidence of the role of diet in causing atherosclerosis is already so overwhelming, “assigning a patient to a control group eating the standard American diet could be considered a violation of research ethics.”

Evidence of the value of plant-based diets for managing chronic disease has been available in the medical literature for decades. Walter Kempner at Duke University, John McDougall, the Physician’s Committee for Responsible Medicine, Nathan Pritikin, and Denis Burkitt all warned us that the standard Western diet is the standard cause of death and disability in the Western world. Yet physicians, especially in the US, are still busily staffing the ambulances at the bottom of the cliff instead of building fences at the top.

If you’re not familiar with Dr. Esselstyn’s work, I touch on it in:

Sadly, medical students learn little about these powerful tools:

If you haven’t heard of Pritikin, I introduce him here: Engineering a Cure

An intro to Dr. Ornish: Convergence of Evidence

Dr. Burkitt: Dr. Burkitt’s F-Word Diet

The Cornell-Oxford-China Study: China Study on Sudden Cardiac Death

Dr. Walter Kempner: Kempner Rice Diet: Whipping Us Into Shape

-Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live year-in-review presentations Uprooting the Leading Causes of DeathMore Than an Apple a DayFrom Table to Able, and Food as Medicine.

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