Last week, the British Medical Journal published a bombshell critical analysis of the flawed scientific process behind the American dietary guidelines, written by Nina Teicholz.1
In two separate published commentaries, David Katz2 took some exception to Teicholz conclusions. I quote only the first of these:
I am rather stunned that the BMJ published a journalist’s commentary about the work of the 2015 United States Dietary Guidelines Advisory Committee as if it were an authoritative rebuttal. The transgression is particularly glaring since this commentary by a non-scientist purports to tell BMJ readers whether or not the work of the DGAC is…scientific. It’s as if someone selling horse paperweights had been invited to critique the Olympic equestrian team. …
With all due respect to the author in question, she is not a nutrition expert, and not a scientist. … If the DGAC report is valid, which it is, it calls into question her own conclusions- as well it should. She may therefore have suspect motives in seeking to discredit this work. …
I confess, I was stunned then, as now, that what was once rarefied territory for truly expert opinion is being allocated so indiscriminately. The notion that the opinion of one journalist with a book to sell is in any way a suitable counterweight to the conclusions of a diverse, multidisciplinary, independent group of scientists who reviewed evidence for the better part of two years; who have been adjudicated by a jury of qualified peers; who were screened assiduously for any actual or apparent conflict of interest; and who relied upon knowledge and judgment cultivated over decades of relevant work- is nearly surreal.
The DGAC very correctly draws conclusions from the weight of evidence, including diverse trials, and the real-world experience of large populations, such as the Blue Zones.3
For reasons that will become clearer, it is necessary to dismantle this unfortunate piece of rhetoric point-by-point.
First: Katz’s criticism that Teicholz is a journalist, not a scientist, and therefore, her opinion does not hold weight. I think that this view is highly contradictory given Katz’s own repeated citation of journalists–a pattern of citation that has been largely erroneous, suggesting, at least in Katz’s case, not that journalists should be barred from scientific debate, but that Katz’s has a history of misunderstanding and misreading them.
To begin, it is worth pointing out that a writer that Katz routinely defers to, Michael Pollan, is, like Nina Teicholz, also a journalist. Indeed, Katz used Pollan’s ideas as his central criterion for evaluating the value of the DGAC report–even though Pollan explicitly outright rejects nutritional science as a means of formulating food guidelines. Indeed, in June of this year, Katz cites Pollan approvingly in precisely this respect:
“We have managed to invent an unending variety of junk foods, each under the alo of some particular nutrient “virtue”: low fat; low carb; low fructose; vitamin fortified; gluten free. We have invented a parade of ways to eat badly, and are, predictably, mostly fatter and sicker as a result. … [However,] the DGAC decided to de-emphasize nutrients altogether, and instead to emphasize the very items we have been overlooking, foods and dietary patterns. … The 8 years of history since Michael Pollan wrote about “nutritionism” in the New York Times have judged his insight to be of profound importance.”4
These claims are surprising, since this citation of Pollan’s ideas is in direct contradiction with the approach taken by the DGAC. For example, in the DGAC report, a cursory search reveals 256 instances of the phrase “saturated fat”, 328 of “sodium”, and 405 of “calorie”. Such technical words are, as we would put it in the language of medicine, pathognonomic of nutritionism–that is, use of such words identify, beyond a doubt, these guidelines as nutritionist. To be clear: any dietary guidelines suspicious of the pitfalls of nutritionism will not make the bulk of its recommendations on the basis of a highly technical nutritional science. In the very same article that Katz quotes approvingly, Pollan states:
“Let culture be your guide, not science.”5
So, one begins to wonder whether Katz has actually read Michael Pollan or merely writes with second-hand familiarity–or if the purpose of citing Pollan ideas in relation to the DGAC was a desperate mystification of a very popular idea. Katz cites Pollan to say the opposite of what Pollan actually says.6
All of this goes to show two points. Even though Katz decries the publication a journalist’s criticism of DGAC:
- He himself appeals to the authority of a journalist, Michael Pollan, in the defense of the DGAC; and
- The ideas of the journalist in question radically contradict the point that Katz is trying to make.
Closer to the present:
After lambasting Teicholz for being a journalist–and for having the gall to pose well-researched critical questions to nutritional experts–Katz proceeds to appeal to the authority of yet another journalist, this time Dan Buettner, of the Blue Zones fame, to show that the DGAC, contrary to what Teicholz says, is good:
“The DGAC report is excellent, and represents both the weight of evidence, and global consensus among experts. It is entirely in line with the persuasive experience of Blue Zone populations.”
So, in the very same article as Katz ridicules the publication of the work of a “non-scientist” “journalist”, he cites the work of a second non-scientist journalist to contradict the findings of the first journalist (who, to Katz, didn’t have credibility in the first place, mind you). So perhaps what Katz means is that only journalists that he doesn’t agree with shouldn’t have their work disseminated.
Notwithstanding all of this, is the DGAC in fact “entirely in line with the persuasive experience of Blue Zone populations”?
Sadly, no, Buettner’s work contradicts the DGAC, just as Pollan’s does. In the The Blue Zones Solution, Buettner writes:
“Small amounts of sheep’s milk or goat’s milk products— especially full-fat, naturally fermented yogurt with no added sugars— a few times weekly are okay. Goat’s and sheep’s milk products do figure prominently in the traditional menus of both the Ikarian and Sardinian Blue Zones.”
On the other hand, the DGAC says:
“The overall body of evidence examined by the 2015 DGAC identifies that a healthy dietary pattern is higher in vegetables, fruits, whole grains, low- or non-fat dairy. …”7
Thus, Buettner’s work seems not to contradict, but validate Teicholz’s critique of the diet-heart hypothesis: there are documented, modern populations consuming a traditional cuisine rich in full-fat dairy products, whose rate of chronic disease is exemplarily low and whose life expectancies are unusually long. If so, this certainly casts doubt on the nutritionistic and possibly cherry-picked impression posed by the DGAC report.
So, now we have not just one, and not just two, but three journalists whose work shouldn’t be allowed to be published or cited.
Indeed, the number of intelligent, diligent, and highly compelling critics of the idea that saturated fat is unhealthy numbers in the hundreds. Even the Academy of Nutrition and Dietetics, the organization that certifies registered dietitians in the United States, recommended dropping saturated fat from the list of forbidden macronutrients. The AND was ignored.8
Based on the preceding, we might pose the following question: if David L. Katz consistently misreads the work of journalists, what is the chance that he appropriately reads Teicholz’s work–or, for that matter, the scientific literature? Because Katz chooses to attack persons and credentials rather than arguments, I personally feel that I have only this history of obvious errors and inconsistencies (to name but a few) to judge the opinion of the man. For science’s sake: I would think it better were his target arguments rather than persons.
Perhaps not coincidental: it is worth noting that Katz’s NuVal system—a system that he claims to be his “life’s work”9—is based on the Dietary Guidelines for Americans.10 This fact may put into context the vigor with which Katz attacks those who publish scientific critiques of the guidelines. (These attacks indeed seem be escalating. For example, Katz recently wrote a column calling Teicholz and her associates “parasites” and calling their writing dangerous, moving into rhetorical territory that I find disturbing.)11
Now, I have privately noticed several other and perhaps more serious errors or inconsistencies in Katz’s popular articles that I have not had the time to address directly here. These appear to be both highly pertinent to present debates and, due to Katz’s prominence in the popular press, important to highlight for the sake of deflecting popular misinformation. Therefore, in Part 2 of this series of posts, I will highlight these and show how they relate to continued debates over the dietary guidelines. More importantly, I will set NuVal (and especially, the errors that make it seem like a good idea) against the backdrop context of an emerging, anti-nutritionistic dietary-culinary paradigm currently making headway among American food writers and American popular culture. This new paradigm is scientifically exemplified by Brazil’s new dietary guidelines, a revolutionary departure from the advice given by America’s nutritional authorities for the past 50 years.12
In the meantime, I must focus on not failing medical school. When I do have the time to make my next post, I can only hope that my being a medical student, rather than an “expert”, does not preclude me from being taken seriously when I make carefully constructed arguments based on a demonstrated, serious reading of the literature. If I am not mistaken: such arguments, and not letters after one’s name, are the real stuff of science.
In Food Rules, Pollan goes further, even more radically skeptical of and opposed to Katz’s approach to nutrition: “I learned that in fact science knows a lot less about nutrition than you would expect–that in fact nutrition science is, to put it charitably, a very young science. It’s still trying to figure out exactly what happens in your body when you sip a soda, or what is going on deep in the soul of a carrot to make it so good for you, or why in the world you have so many neurons–brain cells!–in your stomach, of all places. It’s a fascinating subject, and someday the field may produce definitive answers to the nutritional questions that concern us, but–as nutritionists themselves will tell you–they’re not there yet. Not even close. Nutrition science, which after all only got started less than two hundred years ago, is today approximately where surgery was in the year 1650–very promising, and very interesting to watch, but are you ready to let them operate on you? I think I’ll wait.” How can Katz cite Pollan so glowingly and yet be so unaware of Pollan’s ideas? ↩
“If it isn’t quite my life’s work, it is a whopping big chunk. Or, to use my favorite metaphor, if my life’s work is a levee to contain and turn a floodtide of obesigenic and morbidigenic factors, NuVal is the best and biggest sandbag I’ve been able to contribute to it. Hefting it into its current position has required years of arduous effort.” I take this paragraph to translate, roughly, as: “NuVal is my life’s work.” ↩
Among the recommendations: a simple list of 10 steps, published in both English and Portuguese:
- Make natural or minimally processed foods the basis of your diet
- Use oils, fats, salt, and sugar in small amounts when seasoning and cooking natural or minimally processed foods and to create culinary preparations
- Limit consumption of processed foods
- Avoid consumption of ultra-processed products
- Eat regularly and carefully in appropriate environments and, whenever possible, in company
- Shop in places that offer a variety of natural or minimally processed foods
- Develop, exercise and share culinary skills
- Plan your time to make food and eating important in your life
- Out of home, prefer places that serve freshly made meals
- Be wary of food advertising and marketing
Praised by food writers as diverse as Marion Nestle and Yoni Freedhoff–just this year Vox.com published a piece on the Brazil’s guidelines (entitled: “Brazil has the best nutritional guidelines in the world”) where, in conclusion, they write:
All this amounts to the Brazilian food guide’s “golden rule,” which you’ll note reads like something in a Michael Pollan book:
“Always prefer natural or minimally processed foods and freshly made dishes and meals to ultra-processed foods. In other words, opt for water, milk, and fruits instead of soft drinks, dairy drinks, and biscuits, do not replace freshly prepared dishes (broth, soups, salads, sauces, rice and beans, pasta, steamed vegetables, pies) with products that do not require culinary preparation (packaged soups, instant noodles, pre-prepared frozen dishes, sandwiches, cold cuts and sausages, industrialised sauces, ready-mixes for cakes), and stick to homemade desserts, avoiding industrialised ones.”
See: http://www.vox.com/2015/2/20/8076961/brazil-food-guide, http://health.usnews.com/health-news/blogs/eat-run/2015/02/23/americans-dietary-guidelines-need-a-brazilian, & http://www.foodpolitics.com/2014/02/brazils-new-dietary-guidelines-food-based/ ↩