I woke up one morning last week to a bunch of emails from random people, all suggesting that I check out the same article. A really smart and thorough girl wrote a critique of The China Study which resonated with me. I've been sent a few critiques of the China Study before, but none of them were compelling, unlike Denise's.

I may have an ego about some things, but diet isn't one of them; it's too important. I'm happy to be wrong about what I eat if it means that I can improve my diet, and thus improve my health and my longevity. So I read the critique carefully and left it thinking that I'd likely start eating meat again.

I don't have the time or inclination to become an expert on diet. It takes a lot of time and focus, and the research just isn't interesting enough to me. So instead, like many other fields, my approach is to find the person who seems to be the most knowledgeable and follow their lead. Until I read the critique, that person was T Colin Campbell, author of The China Study.

T Colin Campbell is an easy choice because the China Study is the biggest study on human health ever conducted, and he was one of the scientists who conducted it. I'm not sure what sort of credentials could exceed that.

Still, experts can be wrong. I emailed Dr. Campbell to ask his opinion on her piece. He read it and replied with this, which I have been given permission to publish here:

Dear Tynan,

I don't have time to review every comment but did quickly scan the text. This analysis seems very impressive, especially given the writer's young age with no training in nutritional science (see her web page).

She claims to have no biases--either for or against--but nonetheless liberally uses adjectives and cutesy expressions that leaves me wondering.

As far as her substantive comments are concerned, almost all are based on her citing univariate correlations in the China project that can easily mislead, especially if one of the two variables does not have a sufficient range, is too low to be useful and/or is known to be a very different level of exposure at the time of the survey than it would have been years before when disease was developing. There is a number of these univariate correlations in the China project (associations of 2 variables only) that do not fit the model (out of 8000, there would be) and most can be explained by one of these limitations.

A more appropriate method is to search for aggregate groups of data, as in the 'affluent' vs. 'poverty' disease groups, then examine whether there is any consistency within groups of biomarkers, as in considering various cholesterol fractions. This is rather like using metanalysis to obtain a better overview of possible associations. I actually had written material for our book, elaborating some of these issues but was told that I had already exceeded what is a resonable number of pages. There simply were not enough pages to go into the lengthy discussions that would have been required--and I had to drop what I had already written. This book was not meant to be an exhaustive scientific treatise. It was meant for the public, while including about as much scientific data and discussion that the average reader would tolerate.

She also makes big issues out of some matters that we had no intent to include because we knew well certain limitations with the data. For example, only 3 counties (of the 65) consumed dairy and the kind of dairy consumed (much of it very hard sun-dried cheese) was much different from dairy in the West. It makes no sense to do that kind of analysis and we did none, both because of the limited number of sample points and because we discovered after the project was completed that meat consumption for one of the counties, Tuoli, was clearly not accurate on the 3 days that the data were being collected. On those days, they were essentially eating as if it were a feast to impress the survey team but on the question of frequency of consumption over the course of a year, it was very different. Still, the reviewer makes a big issue of our not including the data for this county as if I were being devious.

In short, she has done what she claims that should not be done--focusing on narrowly defined data rather than searching for overarching messages, focusing on the trees instead of the forest.

I very carefully stated in the book that there are some correlations that are not consistent with the message and, knowing this, I suggested to the reader that he/she need not accept what is said in the book. In this very complex business it is possible to focus on the details and make widely divergent interpretations but, in so doing, miss the much more important general message. In the final analysis, I simply asked the reader to try it and see for themselves. And the results that people have achieved have been truly overwhelming.

One final note: she repeatedly uses the 'V' words (vegan, vegetarian) in a way that disingenuously suggests that this was my main motive. I am not aware that I used either of these words in the book, not once. I wanted to focus on the science, not on these ideologies.

I find it very puzzling that someone with virtually no training in this science can do such a lengthy and detailed analysis in their supposedly spare time. I know how agricultural lobbying organizations do it--like the Weston A Price Foundation with many chapters around the country and untold amounts of financial resources. Someone takes the lead in doing a draft of an article, then has access to a large number of commentators to check out the details, technical and literal, of the drafts as they are produced.

I have no proof, of course, whether this young girl is anything other than who she says she is, but I find it very difficult to accept her statement that this was her innocent and objective reasoning, and hers alone. If she did this alone, based on her personal experiences from age 7 (as she describes it), I am more than impressed. But she suffers one major flaw that seeps into her entire analysis by focusing on the selection of univariate correlations to make her arguments (univariate correlations in a study like this means, for example, comparing 2 variables--like dietary fat and breast cancer--within a very large database where there will undoubtedly be many factors that could incorrectly negate or enhance a possible correlation). She acknowledges this problem in several places but still turns around and displays data sets of univariate correlations. One further flaw, just like the Weston Price enthusiasts, is her assumption that it was the China project itself, almost standing alone, that determined my conclusions for the book (it was only one chapter!). She, and others like her, ignore much of the rest of the book. Can any other diet match the findings of Drs. Esslestyn, Ornish and McDougall, who were interviewed for our book (and now an increasing of other physicians have done with their patients)? No diet or any other medical strategy comes close to the benefits that can be achieved with a whole foods, plant based diet.

I also know that critics like her would like nothing better than to get me to spend all my time answering detailed questions, but I simply will not do this. As we said in our book, no one needs to accept at face value what I say. Rather, as we said in the book, "Try it" and the results will be what they are. So far, the reports of positive benefits have been nothing less than overwhelming.

I hope this helps, although it was written in haste.

Colin

I also heard back from Denise. She very reasonably cautioned me against changing my diet based only on her critique, unless I was having problems as a vegan, and added this:

He's absolutely right that I only posted univariate correlations -- in fact, an epidemiologist pointed this out as well as a flaw in my analysis -- but what I posted was nowhere near the full extent of my data-crunching. [...] I ran multiple variable regressions on the data and it not only confirmed what I demonstrated through simpler graphs, but actually revealed more pronounced inverse relationships between animal foods and diseases (especially heart disease). I'll be compiling the results of the MRAs I ran, since it seems to be a sore point and perceived weakness in my critique, and posting them in a future blog entry.

So here's what I think about everything:

I think I have to trust that Dr. Campbell is the authority on the subject. As he said, with so many correlations, there well always be outliers. That's the truth of any large survey or study, and to expect otherwise is unreasonable. Denise doesn't purport to have studied the entire data, so no matter how much I respect her work, as both she and Dr. Campbell agree, it's not necessarily wise to base a diet change on it.

That said, I don't believe that Denise has any connection with the dairy industry, and I wish Dr. Campbell didn't accuse her of it. She appears to be nothing but genuine to me (and doesn't eat dairy herself). Even if she was associated, I think it's irrelevant. Reasoning stands independent of affiliation. Denise also wrote a response to this point, but in the interest of keeping things as succinct as possible and focusing on the science, I've left it out.

Dr. Campbell is sometimes accused of making rather obvious mistakes or having an agenda. I don't believe that this is true either. I've had the fortune of knowing a lot of people in positions of high accomplishment and have universally found such conspiracy theories to be false. Fakes and people prone to gross oversight just don't make it that far.

Maybe the most important factor is this: there isn't a perceptible downside to eating a healthy vegan diet. I've tracked my diet meticulously over multi-day periods and found that I exceed, often drastically, all required nutrients. Beyond that, I feel as good as I ever had eating my diet, although I will admit that I have felt equally excellent when eating meat. Sugar and flour, on the other hand, are certainly dangerous and negatively affect how I feel.

So I remain a healthy vegan. Other than my twice monthly meat-meals (which fall under the 5% admitted by Dr. Campbell as not affecting health), I only eat whole plant based foods. No flour, no sugar. If you're new to how I eat and my reasoning, read this post about the Max Diet.

If this is an interesting topic to you, I'd highly suggest you read The China Study and Denise's Blog.