I didn’t want you all to have to wait all weekend for the truth: Walter Willet didn’t really say, “I’ve never met a statistical person I didn’t like,” but he is sort of the Will Rogers of nutrition.
The Will Rogers of nutrition?
Everybody likes him, me included. Like Will Rogers was about politics, Willett is a staunch nutrition middle-of-the-roader who thinks fat it not so bad after all, but hey now, let’s not go any kind of crazy here, because saturated fat will still kill you in a New York minute probably maybe.
I spent a lot of time with him earlier this year—okay, really just his book, but his book is so sweet and personal that I felt just like I was sitting at the master’s feet—which were clad in my imagination in the most sensible of shoes—as he unfolded for me the saga of nutritional epidemiology.
What I’m about to say is said with all due respect to the man himself (he’s basically created a whole freekin’ discipline for goodness sake). This is simply my reading of a particular text located within a particular context, i.e. this is what happens when they let English majors into science programs.
There are many reasons why nutritional epidemiology may not be up to the task of giving us a sound basis for nutrition policy. But why take my word for it? If you want to understand the heart of nutritional epidemiology—the driving force behind our bold 40-year march in the misguided direction of one-size-fits-all dietary recommendations—you must read Walter Willett’s Nutritional Epidemiology. It is a book I love more every time I read it, and I say this in all sincerity.
The exciting cover graphics merely hint at the fabulousness that awaits inside!
While I suppose it was written as a sort of textbook, and it is certainly used as one, it doesn’t really read like a textbook. It is part apology and part defense, and is much more about “why” than “how.” And the “why?” that it tries to answer to is “Why apply the techniques of epidemiology to nutrition and chronic disease?”
In this regard, it is a touching masterpiece. Walter Willett, MD, DrPH is a professor at the Harvard School of Public Health and at Harvard Medical School. He is considered by many to be the father of nutritional epidemiology. To stretch the analogy, you can think of nutritional epidemiology as his child. Reading the book this way, it almost moves me to tears (again, not joking*), for I find this book to be a father’s sweet and sad paean to a beautiful prince full of promise, who has grown into a spoiled, churlish, and lazy adult, unfit to rule the kingdom, but with too much of the dreams of many poured into him to banish altogether. And the dreams of the father are the most poignant of all.
Apparently, to Willett’s eternal dismay, the whole field got started off on the wrong foot by focusing on dietary cholesterol (as a cause) and serum cholesterol (as an outcome), associations—as we now know—that turned out to be weak, inconsistent, nonexistent, or even the inverse of what was expected (pp. 5-6, 417-418) . We now know that sub-fractions of serum cholesterol affect heart disease risk differently (LDL-C vs HDL-C, for instance) and that different foods affect different aspects of serum cholesterol differently, making the relationship to overall heart disease risk even more obscure, which seems to be par for the course in this field, as Willett readily admits.
Here, according to Willett, is what we don’t know and can’t do in nutritional epidemiology:
- We don’t know any given individual’s true intake. It can only be estimated with greater or lesser degrees of error. (p. 65)
- We don’t know any given individual’s true status for a nutrient. Ditto above. (p. 174)
- We don’t know the true nutrient content of any given food that a person might eat. Double ditto. (pp. 23-24)
- We don’t know what factors/nutrients in a food may operate together to prevent/cause disease. Similarly, we don’t how foods commonly found together in dietary patterns may operate together to prevent/cause disease. (pp. 15, 21-22, 327-328)
- We have a really hard time separating calorie intake from nutrient intake (Ch. 11). Ditto nutrients and food patterns, food patterns and lifestyle patterns, etc. (pp. 10, 15, 22)
- We can’t separate metabolic consequences of food intake patterns from the food itself, i.e. what we are looking at in any given data set is really metabolism of food, not food. (p. 15)
- We don’t know what really causes the chronic diseases we study in nutrition epidemiology (p. 12); age, genetics, education, income, and lifestyle factors may influence, modify, or be more important than any dietary factor in the origins of these diseases (pp. 10, 15).
- We can’t distinguish between causal and coincidental associations. Furthermore, weak associations could be causal; strong associations can be coincidental (p. 12).
- Associations we do find are likely to be weak; we will often find no associations at all. Even if we do find statistically significant associations between nutrients and disease, they may be clinically or practically irrelevant and should not necessarily be used to make public health recommendations. (pp. 12-14, 21).
But wait! Willett cries. Don’t give up! This book is also a defense of those shortcomings—although one blinkered by what I must assume is Willett’s love for the field. I am always a little touched and frustrated by the section on why we find so many instances of lack of association between an ostensible nutritional cause and a disease outcome in nutrition epidemiology. Willett meticulously lists the possible reasons one by one as to why we may not be able to “observe a statistically significant association when such an association truly exists” (pp. 12-14). At no time does he venture to offer up the possibility that perhaps—and how would we know one way or the other?—no such association does truly exist.
A new edition of the book is coming out; this should make the old edition cheap in comparison. I won’t read the new edition because I’m afraid it would ruin my romance with the old edition, which is the one I recommend to you.
If you think Gary Taubes is “a poisonous pea in an ideological pod” (as I’ve heard him called), read this book (especially Ch 17 on “Diet and Coronary Heart Disease”). On the other hand, if you think population studies investigating nutrition and chronic disease are basically a gigantic undifferentiated crock of malarkey, read this book. Why? Because there are no clear answers and no real heroes. If you want to know the strengths and weakness of nutritional epidemiology, best to hear them outlined in excruciating and loving detail by Willett himself.
You don’t have to read it cover to cover. Skip around. You’ll learn in passing some methodology behind the folly of trying to forge links between specific nutrients in food to long-term chronic diseases that have multiple and complex origins (just the sections on how we collect information about what we think people are eating are eye-opening in that regard—Ch. 4-8). But I think (I hope) you’ll also hear the voice of a father wise enough to know that children are—must be—brought into this world on grand faith, one that hopes that they will make the world a better place than before, and that his child—nutritional epidemiology—is no different. Willett believes in this child and the book is a statement of that faith.
Please draw your own conclusions, here’s mine: Faith is not science.
Any parent out there knows this: you seem at first to have a child of your own, but you end up sending an adult out into the world who is no longer yours and never really was. The mistakes, limitations, failures, shortcomings belong only to that grown child, not to the parent. But still. It may be hard to acknowledge the fact that your precious one is no better than the other kids and probably won’t save the world. Sometimes, when I’m reading this book—when I’m supposedly studying for an exam—I am caught unawares by the sighs of disappointment, the rally of excuses, and finally the prickly justifications: The prince must be allowed to rule; the king knows he’s a weak little louse, but he’s all we’ve got.
I know—and any of us who are students of literature know—that this is the king’s tragic flaw. The prince can’t save the kingdom; the empire must crumble. But here is the king, holding brick and mortar together through sheer force of will, somehow acknowledging and somehow—at the same time—unaware, that this particular castle was built on sand in the first place. In this book, I hear Willett’s love for a hopelessly flawed field, a touching declaration of blind optimism, and I love this book, and I deeply respect the man himself, for showing that to me.
Note: I don’t expect anybody but dweeby English majors to get the title of this post, but for dweeby wanna-bees, see T. S. Eliot’s “The Love Song of J. Alfred Prufrock.” It just makes my heart sing with joy that Willett refers to his diet of preference as the “prudent” diet.
Stay tuned for N of 1 Nutrition: Part 4, when you’ll hear Dr. Roger J. Williams say:
“Nutrition is for real people. Statistical humans are of little interest.”
*Admittedly, it could be eye strain. I am OLD.
References:
Page numbers and chapters refer to the following edition:
Willett, W. Nutrition Epidemiology, 2nd ed. New York: Oxford University Press, 1998.
Eathropology 
Hi Adele, Greetings from the Gary Taubes Fan Club (FB). I don’t know what took me so long to subscribe to your blog.
What do you all talk about in the Gary Taubes fan club? Do you take bets on which university will be the first to grant him an honorary PhD in General Smartness?
Glad you found me!
Home is where one starts from.
As we grow older, the world becomes stranger.
Love is most nearly itself when here and now cease to matter.
Old men ought to be explorers
Here and now do not matter.
We must be still and still moving.
Into another intensity
for a further union, a deeper communion
Through the dark cold and empty desolation
the wave cry, the wind cry, the vast waters
of the petrel and the porpoise.
In my end is my beginning.
Maybe we are at the end of the beginning of the Diet Wars. It feels that way to me. Can’t explain it.
But something has shifted…
Adam, thanks for this. I love this passage (admittedly, I’m a complete sucker for anything TSE has written). When poetry and nutrition come together, something must be shifting. When my dear friend Anna Kelles and I were trying to find the path for HNC that felt right to both of us (she was raised a vegetarian, T. Colin Campbell is a family friend), we ended up sending each other little snippets of poetry. For whatever reason, it seemed the only way to express what we were trying to get at.
Thanks! I’m heartened to see all the love for TSE in these comments. Nerd alert: my high school yearbook quote was “All is always now” from Burnt Norton.
Cool to hear about how poetry brought you and Anna together. I’m convinced that 95% of the discord in the Diet Wars is emotional. Most people just want to feel listened to and respected. The “facts” ain’t all that important to us, even if we think they are and believe they are. After all, our beliefs are probably mostly arbitrary and culturally determined, and they may not actually reflect “nature’s truth” or may reflect it only glancingly.
But our humanness binds us together. And so maybe empathy and compassion, rather than the perfect argument or perfect scientific study, will prove to be our most potent elixir.
Beautifully said, Adam. I agree about the emotional component of the “diet wars.” What weirds me out on a regular basis is how emotional “scientific” arguments get, but–conversely and ironically–how quickly the scientists who are foaming at the mouth reject the notion that doing science is not, in fact, an objective activity. I have a deep and abiding faith in science–although this phrase sounds like it might be an oxymoron–but that faith is grounded in the wondrous ability of science to prove us all wrong eventually–me and you included. I swear, if all of our nutrition scientist/bloggers/writers/pundits had to stand in front of a roomful of intelligent 14-year-olds and make their case, the diet wars would acquire a level of humility henceforth unheard of. (For those who have not had this experience, an intelligent 14 yo has a BS detector the size of Detroit and s/he can find and expose–and if necessary, filet–any moral/emotional/psychological/intellectual weakness in any adult in less time than it takes for that adult to clear his/her throat. This is why parents find their children’s teenage years so difficult.)
Ooo. Surly snarky 8th graders would be the BEST at this game!
Forget the broken “peer review” system. If you can’t convince a roomful of texting, sardonic teens that you have something important to say, then you don’t get published!
LOL, the Eliot reference is really the only part I did get 🙂
Do you think a non-scientist could read this fabulous Willett book and gain anything from it?
Well, I’m a non-scientist, although I am relatively smart, compared to, say, a pile of rocks. Mostly what I am is a reader. To read something closely is to read it for both literal meaning (the author chose particular words) and contextual meaning (the author is a person, specifically located in time/place). As a former teacher, I think I read very sympathetically; in other words, I always assume the writer has something important to say and is trying to say it. So here’s what Willett actually says:
“Moreover, apparently clear dose-response relationships can easily be the result of bias or confounding.” (You don’t have to know the technical meaning of bias or confounding to get his meaning.)
“Even if the intake of a specific nutrient is convincingly shown to be related to risk of disease, this is not sufficient information on which to make dietary recommendations.” (Again, crystal clear, but raises the question–which is never answered–okay WW, what IS “sufficient information”?
“Excess body fat is a powerful risk factor for CHD [coronary heart disease] and may be quantitatively more important than any specific aspect of dietary composition.” (No mistaking his meaning here either, in addition to raising the question, “What causes excess body fat?” Note that this is the exact same conclusion that NIH researchers–who were ridiculed in the press–came to in 1980 when they released “Toward Healthful Diets” as a countermeasure to the first Dietary Guidelines.)
The book definitely has some mathy parts, but it is surprisingly readable. I think the book is most valuable as a way of seeing that nutrition epidemiology is being put to a task–creation of public health policy–for which it is not suited. Gary Taubes argues against the usefulness of nutrition epidemiology as a science; WW is definitely arguing for its usefulness. Yet, they are very much saying the same thing! One last quote: “Data relating intake of specific foods to risk of CHD are extremely limited.” GT could have said that himself. So rather than throw the nutrition epi baby out with the Dietary Guidelines bathwater, maybe we need to go back to the beginning and understand what it can and can’t do–not from a critic (like GT) but from someone who truly loves the field, Walter Willett himself.
I’m not sure that answered your question 🙂
This post is terrific, Adele. I don’t know whether I will read the second edition but you are right. Nutritional Epidemiology is a masterpiece. And Walter’s failure to adhere to its high principles leaves me also with a sadness and the sense of our own limitations. I probably overdid it, calling my post “Crimson Slime” ( http://wp.me/p16vK0-cM ) — it’s already dated so I will change the name — but the stuff he puts his name to is not just bad but damaging. In the end, though, you are right. It is hard to get angry at Walter Willett.
On Eliot, it is generational. Even Physics majors (as I was at the time) knew J. Alfred Prufrock. It was the song of that stage of growth after high school (whose theme was Catcher in the Rye) and some of us saw that it was Eliot’s best work although they tried to tell us it was a prelude to his mature work which we recognized as pretentious and just right for the National Lampoon: (“We will get up and go from here/and when we have gone, we will be someplace else” or something like that).
Thanks Richard, that’s quite compliment coming from someone just as long-winded as I am. It is sad that we’ve poured so much money into these efforts. As I looked for a new advisor this summer (my advisor left to take a position at another university), I visited the folks in nutrition biochem (they seem less concerned about my policy positions than the folks in nutrition epi) and found they had very little funding available. Why? Apparently, the bulk of it goes to nutrition epi. Sad stuff.
“We will get up and go from here/and when we have gone, we will be someplace else” – If that wasn’t it, it should have been. It’s brilliant.
I will try to find it on line but that is definitely the idea. My wife moved my box of old National Lampoons to the garage…or worse.
I am the mother of a physics major. I am in awe of him, while banging my head in dismay as he walks into the wrong math class and sits through the whole things, wondering why it’s not what he was expecting. I brought a Flubber into the world. Just like his late uncle, the engineer.
But I digress.
Adele, I am a new reader who is thoroughly enchanted with your blog: no pat answers, lots of searching and questions–and for this I thank you.
I await your next post with bated breath.
Thanks for the kind words. Yeah, I have one of those–only its music for him (another branch of physics I’m told). I keep thinking “if this is what the smart kid does, what the heck are the dumb ones doing?” I’m glad to have you along for the ride.
Data data data! I cannot make bricks without clay!
Would you settle for a straw man made out of statistics?
I would be looking for the binomial man
Third cousin to the bionic man – skinnier and paler, but smarter
Oh, I had been thinking of Bicentennial man when I wrote that!
Here’s a J Halfred that Willetts ought apply to himself
“I am old, I am old,
I shall wear my trousers rolled.”
I have little respect for Epidemiologists since Bradford Hill’s work on smoking.
My source is The Rise and Fall of Modern Medicine by James le Fanu (Dr) – also Medical correspondent for The Telegraph. Worth a read.
After getting Physics major, I went for Math, Economics and ended as MSc Statistics.
I was shocked and horrified by the sheer statistical incompetence exhibited in MRFIT and WHO reports in early 1980s. I recall reading popular summaries at the time and thinking: these hypotheses MUST be rejected.
Former Physicists & Statisticians laugh at what passes for significant data in “medical” and “nutrition” studies.
I have read some FTL book.
However, Peter Woit’s “Not Even Wrong” about string theory applies to much of the work emanating from NIH.
I do not think I shall read Willets.
Slainte
I have been amused many times by the difference between what statisticians say and what epidemiologist say about data. As a student, I kept thinking I was reading the information wrong when the data didn’t seem to say what the journal article said it was saying. It took me a long time to realize that I should just read the tables and forget the conclusions. I’m afraid you would find “Not Even Wrong” to be pretty aptly applied to much of what we are taught.
oh that’s easy, the statisticians are correct lol Here’s what I have found. Some want to get into epidemiology cause the discovery is fun and they want to save the world. But, really, they want to cover their eyes during the mathy parts. Statisticians otoh, oftentimes fall in love with their favorite techniques, but rarely with a cause or position like the others on the team do.
What I was taught is that epidemiologists “interpret” the data, which I thought meant explain, but I found out was a lot more like “interpreting” poetry than I would have every imagined. Which is really fine by me (taking an educated, context-bound stab at finding meaning in something that may seem without meaning to many is familiar territory to the dweeby English major). Seems to me that interpretations of data, like those of poetry, can be “very likely,” “probable,” “possible, but not likely,” and “highly unlikely.” When you get those “egg yolks are like smoking” papers and you look at the data, it’s like some kid thinking that Prufrock is about a man visiting a museum and wondering if he can eat a peach while he looks at the pretty pictures. If I were teaching I would write on that paper: “This is a highly unlikely interpretation of the material at hand. Go back and see if you can 1) find more evidence to support your statements or 2) find a conclusion that better matches the evidence in front of you.”
Wow! That viewpoint in education seems biased. Where did this assumption come from that statisticians don’t interpret? What I have found is that statisticians are cautious, but from their perspective, it cam really be more about putting the brakes on stupidity.
It does, doesn’t it? My epidemiology books makes quite a point of saying that epidemiology is not just “finely dressed statistics.” On the other hand, we might all be better off if they just let the statistics go naked.
The statisticians I know are like engineers–very logical, very methodical, not the type to go putting fancy underwear on statistics.
This is the way the world ends,
this is the way the world ends,
this is the way the world ends,
Not with a bang, but with a whimper.
Bravo, fellow dweeb.
Spent an extra year gettin’ my BSc in Physics ‘cos I hung wi’ the poets and DramSoc.
But the elegant New Englander is my fave – then I am one of those “Irisch kind”.
Had you not confessed, I’d ‘ve asked.
My rave quote:
What might have been is an abstraction
Remaining a perpetual possibility
Only in a world of speculation.
What might have been is an abstraction
Remaining a perpetual possibility
Only in a world of speculation.
This sounds exactly like the kind of poetry a physics major would love! Weird how those two worlds seem to overlap. I am currently reading Faster than the Speed of Light (Joao Magueijo) and Biocentrism (Lanza & Berman)–fun to switch back and forth between the two.