Editor's Note: There has recently been a flurry of discussion prompted by an article by raw-animal-product advocate Denise Minger, which criticizes The China Studyand attacks its author, Dr. T. Colin Campbell. Minger questions Dr. Campbell's personal motives and attempts to impugn his character.
Dr. Campbell recently took time to review Minger's observations and respond. You can read Minger's original article below, linked at the start of Dr. Campbell's response.
Previously we at VegSource had looked at some of Minger's anti-Campbell rhetoric. One thing we were struck by early on was the fact that Minger apparently removes comments on her blog from scientific researchers who point out the flaws in her reasoning and in her understanding of accepted research methods. In his report below Dr. Campbell notes an example of one researcher whose critical post was removed.
A cancer epidemiologist who says she posted criticism of Minger's methods last week on Minger's blog complained in a posting on VegSource that her critical post first appeared and then was removed from the Comments area of Minger's blog. In fact, Minger herself posted on VegSource in response to this epidemeologist's complaint, and did not deny that the epidemeologist's critical comments had been yanked. After complaining on VegSource about the post disappearing, the epidemiologist's post apparently reappeared on Minger's blog. (Minger subsquently said something about a "spam filter" being at fault.)
As the exchange showed, it was clear to the epidemologist that Minger was out of her depth, and she offered to give Minger some some assistance and teach Minger some proper methods of analysis. In response Minger expressed excitement at hoping to attract professional researchers to help examine Dr. Campbell's data in the future, and see if they can aid Minger in proving Dr. Campbell is wrong in some way. Minger wrote that if she could enlist actual researchers who could help her poke holes in China Study data, "this could be a really great opportunity to grab the attention of the medical community."
About the only community interested in the kind of thing Minger is attempting would be the pro-beef Weston Price Foundation and the meat industry. Minger may find helpers coming forward from those ranks and offering their assistance; many have already tried unsuccessfully for years to attack and undercut the message of Dr. Campbell's life work. On their own website, the Weston Price people express how thrilled they are that Minger has joined in their attempts to discredit Dr. Campbell's work. (In fact, Minger is a fan of the Weston Price Foundation and recommends their work to others. You can read an expose about the Price Foundation at the end of Dr. Campbell's article -- which includes the revelation that Price himself, the founder, actually recommended a vegetarian diet to his family as the most healthy.)
Of course, Minger expresses no interest in publicizing any of her work when it shows Campbell is correct.
We see this often; someone trying to build some credibility on their own by taking aim at the biggest target they can find in hope that they can punch a hole, thus showing themselves to be smart enough to take down the big guy. Unqualified to actually do any kind of study of her own, Minger hopes to find flaws in the peer-reviewed work of researchers from Oxford University, Cornell University, and the Chinese Academy of Preventive Medicine.
Except she's not up to the task of taking on professional researchers who have to work to the most rigorous standards in academia. These are slightly higher than standards for kids blogging on the web.
A critic's post pointing out some of Minger's errors disappears from her blog, and reappears when the critic starts complaining about it elsewhere on the web. Minger then publicly admits that she could use help understanding Dr. Campbell's research, because she doesn't have professional expertise to analyze and interpret the data she's pontificating about.
23-year-old Minger lists her educational and professional qualifications on her Facebook page as writer, Catholic school teacher, summer camp instructor, and "Professional Sock Puppeteer."
So we were mildly surprised that Dr. Campbell felt he needed to take the time to dignify Minger's musings with a response. Still, this is the internet, and I guess sometimes it doesn't hurt to respond, even if the attacks constitute no more than a mosquito bite.
So just in case there are individuals who might feel there was merit to any of Minger's scientific-sounding speculation, here is Dr. Campbell's response:
Reply To Denise Minger
by Dr. T. Colin Campbell, PhD, author The China Study
Ms. Denise Minger has published a critique of our book, The China Study, as follows.
The China Study: Fact or Fallacy? by Denise Minger - article found at: http://bit.ly/9s5pn8
It is both interesting and gratifying that there has been such a huge response, both on her blog and on those of others. This is a welcome development because it gives this topic an airing that has long been hidden in the halls and annals of science. It is time that this discussion begin to reach a much larger audience, including both supporters and skeptics.
I hope at some point to be able to read all of the discussions and the questions that have been raised, but present deadlines and long-standing commitments have forced me, for now, to focus on the most common concerns and questions, in order to respond in a timely manner here.
Kudos to Ms. Minger for having the interest, and taking the time, to do considerable analysis, and for describing her findings in readily accessible language. And kudos to her for being clear and admitting, right up front, that she is neither a statistician nor an epidemiologist, but an English major with a love for writing and an interest in nutrition. We need more people with this kind of interest.
I am the first to admit that background and academic credentials are certainly not everything, and many interesting discoveries and contributions have been made by "outsiders" or newcomers in various fields. On the other hand, background, time in the field, and especially peer review, all do give one a kind of perspective and insight that is, in my experience, not attainable in any other way. I will try to make clear in my comments below when this is particularly relevant.
My response can be divided into three parts, mostly addressing her argument's lack of proportionality--what's important and what's not.
Misunderstanding our book's objectives and my research findings
Excessive reliance on the use of unadjusted correlations in the China database
Failure to note the broader implications of choosing the right dietary lifestyle
Before proceeding further, however, I would like to make a general comment about my approach in responding to Denise. I believe Denise is a very intelligent person, and I can see how she might reach the conclusions she did; this is easy to do for someone without extensive scientific research experience. Having said this, there are fundamental flaws in her reasoning, and it is these flaws that I will address in this paper. Some might wonder, "Why didn't he go through her laundry list of claims and address each one in the same order?" The answer is simple: these claims are derived from the same faulty reasoning, so it is this underlying problem that I will address. I do in fact illustrate this point by addressing one of her claims regarding wheat, and the reader can assume that one could go through a similar exercise with all her claims.
A. Not understanding the book's objectives.
The findings described in the book are not solely based on the China survey data, even if this survey was the most comprehensive (not the largest) human study of its kind. As explained in the book, I draw my conclusions from several kinds of findings and it is the consistency among these various findings that matter most.
First and foremost, our extensive work on the biochemical fundamentals of the casein effect on experimental cancer in laboratory animals (only partly described in our book) was prominent because these findings led to my suggestion of fundamental principles and concepts that apply to the broader effects of nutrition on cancer development. These principles were so compelling that they should apply to different species, many nutrients, many cancers and an almost unlimited list of health and disease responses (e.g., nutritional control of gene expression, multi-mechanistic causation, reversal of cancer promotion but not reversal of initiation, rapidity of nutritional response, etc.). These principles also collectively and substantially inferred major health benefits of whole plant-based foods.
This earlier laboratory work, extensively published in the very best peer-reviewed journals, preceded the survey in China. These findings established the essence of what can be called biological plausibility, one of the most important pillars establishing the reliability of epidemiological research. [Biological plausibility represents established evidence showing how a cause-effect relationship works at the biological level, one of the principles of epidemiology research established by the epidemiology pioneer, Sir Bradford Hill.]
Unfortunately, this issue of biological plausibility too often escapes the attention of statisticians and epidemiologists, who are more familiar with 'number crunching' than with biological phenomena. The first 15-20 years of our work was not, as some have speculated, an investigation specifically focused on the carcinogenic effects of casein. It was primarily a series of studies intended to understand the basic biology of cancer and the role of nutrition in this disease. The protein effect, of course, was remarkable, and for this reason, it was a very useful tool to give us a novel insight into the workings of the cancer process. [Nonetheless, the casein effect, which was studied in great depth and, if judged by the formal criteria for experimentally determining which chemicals classify as carcinogens, places casein in the category of being the most relevant carcinogen ever identified.]
Second, this survey in rural China, based on a very unique population and experimental format (from several perspectives), resulted in the collection of an exceptionally comprehensive database that, to a considerable extent, permitted the testing of hypotheses and principles learned in the laboratory, both mine and others. By 'testing', I mean questioning whether any evidence existed in the China database to support a protective effect characterized by the nutritional composition of a plant-based diet. I was not sure what might be found but nonetheless became impressed with what was eventually shown.
The China project data afforded an opportunity to consider the collective interplay and effects of many potentially causative factors with many disease outcomes--the very definition of nutrition (my definition of nutrition is not about the isolated effects of individuals nutrients, or even foods for that matter). The China project encouraged us not to rely on independent statistical correlations with little or no consideration of biological plausibility. In the book, I drew my conclusions from six prior models of investigation to illustrate this approach: breast cancer, liver cancer, colon cancer (minimally), energy utilization/body weight control, affluent disease-poverty disease and protein vs. body growth rates. Using this strategy, I first inquired whether a collection of variables in the China survey (ranging from univariate correlations to more sophisticated analyses) could consistently and internally support each of these biologically plausible models and, second, I determined whether the findings for each of these models were consistent with the overarching hypothesis that a whole food, plant-based diet promotes health--I could not discuss much of this rationale in a page-limited book intended for the public.
Most importantly, I cannot emphasize enough that the findings from the China project, standing alone, do not solely determine my final views expressed in the book. That's why only one chapter of 18 was devoted to the China survey project, which is only one link in a chain of experimental approaches. I was simply asking the question whether there were biologically plausible data in the China database to support the findings gained in our laboratory, among others. Because of the uniqueness of the China database, I believed that the evidence was highly supportive. One of the unique characteristics of this survey was the traditional dietary practices of this cohort of people. Mostly, they were already consuming a diet largely comprised of plant-based foods, thus limiting our ability to detect an hypothesized plant-based food effect--thus making our final observations that much more impressive.
Third, in the book, we summarized findings from other research groups for a variety of diseases to determine the consistency of our model with their findings, according to my principles and concepts. One of the most compelling parts of this exercise was the fact that so many of their findings, although published in good peer-reviewed journals, had been and were continuing to be ignored and/or distorted, a very disturbing and puzzling phenomenon. This posed for me the question, why? My participation in extensive reviews of the work of others during my 20-year stint working on or as a member of expert committees gave me a particularly rich opportunity to consider these previously published studies. There still is, and for a long time has been, an intentional effort at various levels of science hierarchy to denigrate studies that speak to the more fundamental biology of plant-based diets. The fact that there has been resistance, oftentimes hostile and personal in the lay community, speaks volumes to me.
Fourth, and most importantly, there is the enormously impressive findings of my physician colleagues, which came to my attention near the end of the China project data collection period and which were showing remarkable health benefits of plant-based nutrition, involving not only disease prevention but also disease treatment (alphabetically: Diehl, Esselstyn, Goldhamer, Klaper, McDougall, Ornish, Shintani-and many others since the book's publication: T. Barnard, N. Barnard, Corso, Fuhrman, Lederman, Montgomery, Popper, Pulde, Schulz, Shewman). I cannot overemphasize the remarkable accomplishments of these primary care physicians. In effect, their work affirmed my earlier laboratory research. I should add that I knew none of them or their work during my career in the laboratory, thus was not motivated or biased to find ways to affirm their work.
It was the combination of these various lines of inquiry that made so compelling the larger story told in the book, at least for me. Denise mostly ignores these fundamental but highly consistent parts of my story. In that vein, I strongly believe that the findings of no single study in biology or even a group of similar studies should be taken too seriously until context is established. Biology is not for engineers and number crunchers, as important as they may be, because, compared to their systems, biological response is much more complex and dynamic.
B. The use of 'raw' univariate correlations.
In a study like this survey in China (ecologic, cross-sectional), univariate correlations represent one-to-one associations of two variables, one perhaps causal, the other perhaps effect. Use of these correlations (about 100,000 in this database) should only be done with caution, that is, being careful not to infer one-to-one causal associations. Even though this project provided impressive and highly unique experimental features, using univariate correlations to identify specific food vs. specific disease associations is not one of these redeeming features, for several reasons. First, a variable may reflect the effects of other factors that change along with the variable under study. Therefore, this requires adjustment for confounding factors--mostly, this was not done by Denise. Second, for a variable to have information of value (as in making a correlation), it must exhibit a sufficient range. If, for example, a variable is measured in 65 counties (as in China), there must be a distribution of values over a sufficiently broad range for it to be useful. Third, the variables should represent exposures representative of prior years when the diseases in question are developing. I see little or no indication that Denise systematically considered each of these requirements.
I should point out that when we were deciding to publish these data in the original monograph, we decided to do something highly unusual in science--to publish the uninterpreted raw correlations, hoping that future researchers would know how to use or not use them. We felt that this highly unusual decision was necessary because we were wary of those in the West who might have doubted the validity of data collected in China--we had several experiences to suspect this. But also, we believe that research should be as transparent as possible, simply for the sake of transparency, thus minimizing suspicion of hidden agendas. We knew that taking this approach was a risk because there could be those who, knowing little or nothing about experimentation of this type, might wish to use the data for their own questionable purposes. Nonetheless, we decided to be generous and, in order advise future users of these data, we added our words of caution--written about 1988--as part of our 894-page monograph. I also have repeated this caution in other publications of mine. It seems that Denise missed reading this material in the monograph.
As I was w