Archive for July, 2012

In Defense of Food: My Review

July 24, 2012 at 7:42 am · Filed under In Defense of Food, Science ·Tagged , , , ,

Michael Pollan’s In Defense of Food might best be described as a book which fares best when judged by its cover. Below the title, a reader finds some dietary advice which is not a bad place to start: “Eat food. Not too much. Mostly plants.” There are a few good ideas inside the book, too. It would be easy not to look much deeper, as Pollan’s prose is so lively that most readers won’t want to stop and give things a closer look. However, the reader who does bother to check the details sees that In Defense of Food is not a credible work of nonfiction. Pollan twists facts and misrepresents the way science works in the course of assembling exaggerated, false, and contradictory narratives.

Pollan’s central thesis is that introducing science into our food system has done more harm than good and that the best thing for all of us would be to go back to eating a more traditional diet. It’s fair to point out that nutritional science has led to some mistakes (such as recommendations to replace saturated fats with hydrogenated oils), but Pollan devotes too much of his effort to dismantling his own shallow caricature of science. Pollan’s chief criticism of nutritional science is that it adheres to the ideology of nutritionism, which he defines as the belief that foods can be understood by studying their constituent nutrients. He explains that nutritionism is rooted in the idea that foods are “decidedly unscientific things” (19) and that studying individual nutrients is “the only thing [nutritional scientists] can do” (62). He even puts forth the idea that the goal of nutritional science is to find an “X factor” (178) — a single compound that is responsible for good health — so that food processors can add more of it to their products.

But science — to the people who study it — isn’t defined by the consideration of certain “scientific” things with hard-to-pronounce names. The scientific method is a general process for improving our understanding of the world. It entails using observations to form a hypothesis, testing the hypothesis experimentally, and refining that hypothesis based on the results of the experiment. As far as the scientific method is concerned, oranges are as good a subject to study as vitamin C. And nutritional scientists tend to be aware that human nutrition is too complicated to be explained by a single “X factor.” After all, that’s part of what makes their jobs challenging!

As proof of the malignancy of nutritionism, Pollan points to the various sets of nutritional guidelines which encouraged Americans to reduce their fat consumption. As Pollan explains, these recommendations gave rise to products like the SnackWell’s cookie, which was presumed healthy on the basis of its being fat-free. He contrasts the low-fat guidelines with the theory (put forward by Gary Taubes and others) that weight gain results when the consumption of refined carbohydrates promotes fat storage and overeating. If that theory is correct, he explains, “there is no escaping the conclusion that the [official dietary advice] bears direct responsibility for creating the public health crisis that now confronts us” (59-60).

By the end of the book, he’s moved on to blaming that same public health crisis on overconsumption of cheap sweeteners and added fats, pointing out that Americans have added 300 calories to their daily diets since 1980 and citing a group of Harvard economists who “concluded that the widespread availability of cheap convenience foods could explain most of the twelve-pound increase in the weight of the average American since the early 1960s” (186-187). If both the dietary guidelines and the cheap convenience foods are to blame, then it must be that the guidelines encouraged Americans to eat those convenience foods, right?

Not exactly, as it would happen. For all his insistence that Americans have “an unhealthy obsession with healthy eating” (9), Pollan gives us precious little evidence that we’ve actually been following the official dietary advice. Indeed, a reader of the various guidelines would see that falling prey to the food marketers often meant going against the science-based dietary advice. For instance, the second edition of the 1977 Dietary Goals for the United States, one of the main sets of guidelines which Pollan criticizes, included warnings against overeating and recommended a decrease in consumption of both fats and refined sugars. So while the sugary SnackWell’s cookies might have helped to reduce fat intake, the dietary guidelines were hardly an invitation to eat them without restraint.

It should thus be no surprise that in his quest to fault science-based nutritional advice for our public health crisis, Pollan often misleads readers about what the dietary guidelines actually said. He tells us, for instance, that a literature review “found ‘some evidence’ that replacing fats in the diet with carbohydrates (as official dietary advice has urged us to do since the 1970s) will lead to weight gain” (45). It sounds pretty damning, at least until you look at the actual paper, which, in fact, reported “some evidence” that replacing dietary fats with refined carbohydrates leads to weight gain. Pollan, of course, had a very good reason to leave out the extra word: that little bit in parentheses would have been false if he’d included it. The government recommendations never urged Americans to replace dietary fats with refined carbohydrates. Truth be told, the official dietary advice could have done better here, but a reader of the recommendations would see encouragements to decrease our consumption of a major class of refined carbohydrate (sugars) and to eat more unrefined carbohydrates in the form of fruits, vegetables, and whole grains.

But some falsehoods can’t be made to look true just by neatly hiding the pesky details behind a missing adjective, and Pollan’s book contains some of these ideas, too. Indeed, the notion that nutritional scientists study nutrients to the exclusion of foods is incorrect; the ideology of nutritionism that occupies so much of Pollan’s attention is a straw man. A reader might get the sense that something isn’t quite right when Pollan refers to a few nutritional studies that considered whole foods. On the other hand, the reader might suppose, perhaps those studies are outliers. After all, Pollan tells us that (since 1977) the official dietary recommendations have always been expressed in terms of nutrients rather than foods. As an example, he gives us the 1982 report, Diet, Nutrition, and Cancer, in which the National Academy of Sciences “was careful to frame its recommendations nutrient by nutrient rather than food by food, to avoid offending any powerful interests” (25). The only problem is that it isn’t true. The report contains six “Interim Dietary Guidelines,” only one of which was expressed in terms of nutrients, and two of which were expressed in terms of foods. (Of the remaining three, two were encouragements to keep dangerous substances out of the food supply, and one was a reminder not to drink too much.)

The antidote to nutritionism, as Pollan explains, is “to entertain seriously the proposition that processed foods of any kind are a big part of the problem” (141) and  “escape the Western diet” (142) for a more traditional diet. That’s a bold declaration, considering that “processing” in the food system includes not just things like hydrogenating vegetable oils but also everything from chopping vegetables to slaughtering animals. Pollan reasons that science has made us unhealthy by encouraging us to eat in new ways, but a traditional diet must be healthy because “if it wasn’t a healthy regimen, the diet and the people who followed it wouldn’t still be around” (173). Unfortunately, he thereby misses the rather important point that a diet can be unhealthy without doing away with its eaters. Pollan’s line of argument would, for example, vindicate the diet of white rice that left so many with beriberi. And some day, it may well exonerate the American diet, whose worst health effects tend to show up well beyond reproductive age.

For all that Pollan gets wrong, there is a grain of truth to his message. Though Pollan errs in faulting nutritional science for giving us a license to eat every high-carb, low-fat food that processors might concoct, it is true that it would be a bad idea to assume that a low-fat food is a healthy food. Pollan is probably even right that some people reached that conclusion based on their interpretations of the official dietary advice. However, the lesson to take away from this is not that we should ignore nutritional science but that when we oversimplify our decision-making processes, we leave ourselves particularly vulnerable to cheap marketing ploys. With that in mind, the solution he offers is regrettable. Rather than embracing critical thinking and careful attention to detail, Pollan gives us a few simple rules backed up by the same sort of lazy thinking that he claims to have seen in nutritional science. It should therefore be no surprise that food companies have begun to take advantage of his rules for eating, with Frito-Lay advertising that its Lay’s potato chips have only “three simple ingredients” (less than Pollan’s recommended maximum of five ingredients) and manufacturers reformulating products like Gatorade, Hunt’s ketchup, and Wheat Thins to replace the taboo high-fructose corn syrup with other sugars.

To be fair, a few of Pollan’s rules, such as “eat slowly…in the sense of deliberate and knowledgeable eating promoted by Slow Food” (194) and “plant a garden” (197), will probably prove difficult for food companies to use for their own ends. For the most part, however, these reflect a level of privilege which many people do not have. This isn’t too surprising, as Pollan makes no secret of the fact that he writes for a well-to-do audience when he declares, “Not everyone can afford to eat high-quality food in America, and that is shameful; however, those of us who can, should” (184). That doesn’t invalidate his perspective, but there is nonetheless something a bit distasteful about a bestselling author lamenting the eating habits of people whose lives are worlds away from his own. Absent any indication of a good-faith effort to understand why people might choose to microwave frozen dinners instead of preparing a family meal from home-grown ingredients, Pollan’s work seems less likely to inspire positive social change than, as Julie Guthman puts it, to appeal to “those who already are refined eaters and want to feel ethically good about it.”

Michael Pollan remarks in the introduction of In Defense of Food that had he written the book forty years earlier, it would have been received as “the manifesto of a crackpot” (14). In light of the superficiality of the book’s merits and its loose relationship to the facts, that wouldn’t have been a particularly unfair appraisal. Alas, in the time since the work’s publication in 2008, our collective judgment has proven decidedly less sound. Thanks to its engaging style and appealing commonsense message, In Defense of Food has become required reading for thousands of college students, and its author now stands at the helm of a respected social movement. With the alarming rise in diet-related disease, the time was indeed ripe for someone to fill that leading role. It’s just too bad that it was somebody who mostly gives us the same kind of simplistic solutions and sloppy reasoning that helped to create the problem in the first place.

Also posted at Amazon and Goodreads. For more on In Defense of Food, I recommend the following posts:

You can also look at all of my posts about In Defense of Food.

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Should Americans be spending more on food?

July 13, 2012 at 7:49 am · Filed under In Defense of Food ·Tagged , , ,

Michael Pollan echoes a popular foodie talking point:

For the majority of Americans, spending more for better food is less a matter of ability than priority. We spend a smaller percentage of our income on food than any other industrialized society; surely if we decided that the quality of our food mattered, we could afford to spend a few more dollars on it a week–and eat a little less of it. (187)

This amounts to a textbook case of statistical abuse. When Pollan refers to the small percentage of income Americans spend on food, that doesn’t say anything about the majority of Americans at all. It is, instead, a statement about our collective income (as compared to the incomes of other societies).

To understand this distinction, consider somebody who makes a million dollars a year. To spend 9.9% of that income (a figure Pollan cites in the next paragraph), this person would need to buy $99,000 worth of food in a year. Even assuming this person supports a large family and buys the kind of food that Michael Pollan says we should be eating, that’s a huge amount of food! Thus, people with large incomes will tend to spend a small percentage of their income on food. Moreover, because these people make so much money, their spending patterns are weighted more heavily in the figure than a comparable number of people at the lower end of the income scale*. The point here is that when we look at the percentage of income spent on food, that number is pushed downward by income inequality. Since the United States has a relatively high level of income inequality, this distortion is particularly pronounced in our case.

To look much deeper into the statistics, it would be helpful to be able to look at some actual data. Unfortunately, Pollan doesn’t give a citation on this claim, but when foodies compare food spending among countries, if a source is provided, it’s the USDA’s data on “Expenditures on food and alcoholic beverages that were consumed at home, by selected countries.” This looks at food spending as a percentage of household final consumption expenditures (which is certainly not the same as income). I don’t know for sure that this is Pollan’s source, but since he’s given his endorsement to a similar use of that data before, I’ll say a few things about it here. One weakness of the data shows up right in the title: it’s referring only to meals eaten at home. That means it’s not even clear that it includes the same number of meals in different countries. Looking at the data for 2006, for instance, if (and this is strictly hypothetical because I haven’t seen any data on the number of meals eaten at home) Americans devoted 6.6% of their spending to 14 meals eaten at home per week at home and the British devoted 8.6% of their spending to 18 meals per week, the British and the Americans would actually be putting about the same percentage of their spending toward each meal. Again, this is hypothetical, but if foodies are right when they say that Americans eat too many meals in restaurants or at their desks at work, this could be important.

Another problem with the data lies with the way that household final consumption expenditures are defined. Americans tend to have lower taxes than Europeans and pay for some things out of their pockets that are paid for with taxpayer money in Europe. For example, things like health care, education, and transportation are more heavily subsidized by taxes in Europe than in the United States. This means that those expenses are largely included in household final consumption expenditures for the US, but less so for the European countries. This, in turn, serves to decrease the percentage of household final consumption expenditures which Americans spend on food.

None of this is to say that Americans are spending the ideal amount on food. Nor do I mean to defend everything on which Americans spend money. My point is simply that the comparison of the US to other countries doesn’t support Pollan’s argument very well because the data reflect many differences among the various countries. I don’t doubt that there are significant externalities in the production of food or that food would cost more if these were reflected in the price. However, I don’t see much to be gained by throwing around misleading statistics to overstate the extent to which people are able to pay those costs.

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*To see why, consider a fictitious country with only two people, one making $10,000 and spending $3,500 on food and the other making $150,000 and spending $9,000 on food (these are approximately at the averages of the top and bottom income quintiles for the United States for recent years). One person is spending 35% of income on food and the other is spending 6% of income on food. The population as a whole spends $12,500 of its $159,000 income on food. That’s only 7.9%, much closer to the wealthier resident’s figure.

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Michael Pollan, X factors, and Weston Price

July 10, 2012 at 7:21 am · Filed under In Defense of Food, Science

In In Defense of Food, Michael Pollan promotes the idea that nutritional scientists seek simplistic solutions to our dietary problems. He writes,

Oceans of ink have been spilled attempting to tease out and analyze the components of the Mediterranean diet, hoping to identify the X factor responsible for its healthfulness: Is it the olive oil? The fish? The wild greens? The garlic? The nuts? The French paradox too has been variously attributed to the salutary effects of red wine, olive oil, and even foie gras (liver is high in B vitamins and iron). (177)

It’s telling that he doesn’t bother to tell us who has attributed the so-called French paradox (the fact that the French people are healthier than Americans while eating a diet that goes against mainstream nutritional advice) to these foods. Is it nutrition scientists themselves? Journalists? Food marketers? Somebody on the internet? (The references provide a few scientific studies on related topics, but these, unsurprisingly, offer only modest, qualified conclusions.)

Pollan continues,

But the quest to pin down the X factor in the diets of healthy populations (PubMed, a scholarly index to scientific articles on medicine, lists 257 entries under “French Paradox” and another 828 under “Mediterranean Diet”) goes on, because reductionist science is understandably curious and nutritionism demands it. If the secret ingredient could be identified, then processed foods could be reengineered to contain more of it, and we could go on eating much as before. (178)

Of course, the purpose of nutritional science, even when based on the study of individual nutrients, need not only be to find the “X factor” to cater to food processors. The report Diet, Nutrition, and Cancer, which Pollan writes about at length (and, I’ve argued, misrepresents), provides a good example of this. Although the report identified some compounds in fruits and vegetables which seemed beneficial, the interim guidelines encouraged the consumption of fruits and vegetables (rather than, say, carotenes or vitamin C).

I can’t help but suspect that, of all the hundreds of PubMed results for “French Paradox” and “Mediterranean Diet,” none of them actually claimed to have found this “X factor” of which Pollan writes. In spite of any popular ideas about scientific progress being driven by mad scientists figuring everything out all at once, science tends to be a slow process of incremental progress on complex problems. If anybody knows this, it’s the people who have devoted their lives to the study of science.

Though scientists will rarely talk about finding an “X factor,” Pollan shows surprising sympathy for one researcher who claimed to have found something of the sort, the late Weston Price. Price was a dentist who gave up his practice in the 1930s to travel around the world to study the traditional diets of people who had not yet been exposed to the modern foods that he suspected were responsible for many of society’s problems. Price’s work has since become a favorite talking point of proponents of traditional diets.

Pollan, to his credit, acknowledges that Price “could sometimes come across as a bit of a crackpot” for his bizarre racial theories and tendency to blame all of society’s ills on diet. However, that doesn’t stop Pollan from dedicating five pages of the book to a discussion of Price’s work, which he says “points the way toward a protoecological understanding of food that will be useful as we try to escape the traps of nutritionism.”

Price didn’t use the term “X factor,” but he did devote an entire chapter of his book Nutrition and Physical Degeneration to a substance which he called “activator X” (and which Price’s modern day devotees do call the “X factor”). Price argued that activator X, which is now more commonly known as Vitamin K2, was strongly protective against dental caries. He also provided data to suggest that the level of activator X in a society’s dairy products correlated negatively with mortality due to heart disease and pneumonia. Finally, he shared a single anecdote in which activator X appeared to have cured convulsions in a young child.

Whatever the merits of Price’s ideas about Vitamin K2, it is interesting that Pollan largely chooses to ignore them, mentioning the term “activator X” only in passing. It’s hardly surprising, though, as they wouldn’t fit so well with the idea that the only reason anybody might study specific nutrients is so that processed foods might be engineered to contain more of them. Price, after all, believed that the food supply was overly industrialized in the 1930s. He had no interest in seeing processed foods with more activator X, but he still chose to study the compound.

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The reductionism of nutritional Darwinism

July 5, 2012 at 7:45 am · Filed under In Defense of Food, Science ·Tagged , , ,

Michael Pollan argues in In Defense of Food that we should ignore nutritional science and stick with traditional diets. He explains,

Confounding factors aside, people who eat according to the rules of a traditional food culture are generally much healthier than people eating a contemporary Western diet…I’m inclined to think any traditional diet will do; if it wasn’t a healthy regimen, the diet and the people who followed it wouldn’t still be around. (173)

This is the dietary philosophy which Daniel Engber called “nutritional Darwinism.” The idea behind the name is that people who eat unhealthy diets will be selected out (in the sense of Darwin’s natural selection) of the human population over time.

On the face of it, it might be an appealing idea, but nutritional Darwinism is reductionist in its own way. Namely, it reduces all of human health to the ability to reproduce and raise offspring who can reproduce. If we only know that a group of people has survived on a particular diet for generations, that doesn’t tell us much about how the people tend to die, how long they tend to live, or any non-fatal health problems they may experience. And as the story of beriberi shows, groups of people have survived for generations on traditional diets that had serious nutritional deficiencies.

However, to fully appreciate the weakness of this line of reasoning, consider what it might say about the “Western diet” from which Pollan urges readers to “escape.” Although Pollan contends that this diet is a relatively recent development, it’s not obvious that it can’t survive for a while. There clearly is no shortage of Americans at reproductive age. Moreover, the “Western diseases”–the conditions such as heart disease and cancer that Pollan blames on the Western diet–tend to strike later in life, so they don’t usually interfere with people’s ability to reproduce. This means that there’s no reason to believe that the Western diet will kill off its eaters any time soon. Therefore, if the principle of nutritional Darwinism is to be believed, the Western diet must be healthy!

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