Archive for Science

In Defense of Food: My Review

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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Michael Pollan, X factors, and Weston Price

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

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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Nutrition science doesn’t claim to have all the answers

In In Defense of Food, Michael Pollan explains what he sees as one of the problems with science-based dietary advice:

When Prout and Liebig nailed down the macronutrients, scientists figured that they now understood the nature of food and what the body needed from it. Then when the vitamins were isolated a few decades later, scientists thought, okay, now we really understand food and what the body needs for its health; and today it’s the polyphenols and carotenoids that seem to have completed the picture.

One has to wonder, if the scientists have long been so confident in the completeness of their understanding of human nutrition, why do they continue researching the subject?

It is true that scientists have sometimes expressed undue confidence in an idea. However, the suggestion that nutrition scientists see human nutrition as a solved problem is patently absurd. These scientists continue doing research precisely because they understand that there are many questions remaing about nutrition.

One sees this, for example, in the 1982 report Diet, Nutrition, and Cancer, which Pollan discusses at length. In introducing its interim guidelines, the report explained,

It is not now possible, and may never be possible, to specify a diet that would protect everyone against all forms of cancer. Nevertheless, the committee believes that it is possible on the basis of current evidence to formulate interim dietary guidelines that are both consistent with good nutritional practices and likely to reduce the risk of cancer.

The authors of the report thus readily acknowledged that they didn’t “really understand food.” They issued guidelines anyway on the belief that useful recommendations could be made based on what they did understand.

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Polyunsaturated fats and heart disease

Michael Pollan concludes his attempted takedown of the lipid hypothesis in In Defense of Food by addressing the supposed role of dietary changes in reducing heart disease:

Even if we accept the epidemic of obesity and diabetes as the unintended consequence of the war against dietary fat–collateral damage, you might say–what about the intended consequence of that campaign: the reduction of heart disease? Here is where the low-fat campaigners have chosen to make their last stand, pointing proudly to the fact that after peaking in the late sixties, deaths from heart disease fell dramatically in America, a 50 percent decline since 1969.  Cholesterol levels have also fallen. Epidemiologist Walter C. Willett of the Harvard School of Public Health…cites the increase in consumption of polyunsaturated fats “as a major factor, if not the most important factor, in the decline in heart disease” observed in the seventies and eighties… And so it would appear to be: We reduced our saturated fat intake, our cholesterol levels fell, and many fewer people dropped dead of heart attacks.

Whether the low-fat campaigners should take the credit for this achievement is doubtful, however. Reducing mortality from heart disease is no the same thing as reducing the incidence of heart disease, and there’s reason to question whether underlying rates of heart disease have greatly changed in the last thirty years, as they should have if changes in diet were so important. A ten-year study of heart disease mortality published in the New England Journal of Medicine in 1998 strongly suggests that most of the decline in deaths from heart disease is due not to changes in lifestyle, such as diet, but to improvements in medical care…For while during the period under analysis, heart attack deaths declined substantially, hospital admissions for heart attack did not. (60-61)

The referenced study is “Trends in the Incidence of Myocardial Infarction and in Mortality Due to Coronary Heart Disease, 1987 to 1994.” As the title suggests, this “ten-year study” is actually an eight-year study. That means that Pollan is attempting to debunk claims made about health trends over the course of a few decades by looking at a much shorter period. Moreover, Walter Willett’s claim applies specifically to the seventies and eighties, but a reader who did not bother to check the references would not realize that the period under consideration by Pollan’s “ten-year study” actually only had three years in common with this interval.

This becomes even more problematic when we look at what people were eating. Specifically, let’s look at the amount of polyunsaturated fats in the US food supply (page 65), which is most directly relevant to Willett’s claim.

Amount of polyunsaturated fat in the US food supply, per capita per day. The red lines indicate the beginning and end of the period considered by the NEJM study.

The data show that consumption of polyunsaturated fats increased from 26 grams per person per day in 1970 to 32 grams per person per day in 1985, with most of the increase coming from 1977 and 1985. However, in 1985 polyunsaturated fat intake more or less leveled out, and the net increase over the period under consideration in the NEJM study was only 1 gram. Thus, even if we were to suppose that Willett were right, it’s not clear that we should have expected to see much of a drop in the incidence of heart disease in the study.

Since dietary changes can have long-term effects on health, this doesn’t necessarily mean that Pollan’s argument is completely wrong. Indeed, the distinction he makes between incidence of heart disease and deaths due to heart disease is an important one. However, it’s just not clear how relevant the study he cites really is. The choice of intervals needs to be justified as a part of his argument, rather than hidden away in the references.

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Should communication between pea plants raise tough issues for vegetarians?

I was just about ready to get back into my review of In Defense of Food this week. That is, until yesterday morning, when Michael Pollan tweeted,

Cool piece on how pea plants communicate with one another, possibly raising some tough issues for vegetarians. p2.to/1jpp

The basic science in the blog post, I have to say, is genuinely interesting. The idea is this:

[A] team of scientists from the Blaustein Institute for Desert Research at Ben-Gurion University in Israel published the results of its peer-reviewed research, revealing that a pea plant subjected to drought conditions communicated its stress to other such plants, with which it shared its soil. In other words, through the roots, it relayed to its neighbors the biochemical message about the onset of drought, prompting them to react as though they, too, were in a similar predicament.

Curiously, having received the signal, plants not directly affected by this particular environmental stress factor were better able to withstand adverse conditions when they actually occurred. This means that the recipients of biochemical communication could draw on their “memories” — information stored at the cellular level — to activate appropriate defenses and adaptive responses when the need arose.

Stuff like this is fascinating to me, and I’d love to know more about it. However, I probably won’t look to the New York Times to further enrich myself because the Times seems to have a rule that requires all discussions of plant responses to external stimuli to include a discussion of the ethics of eating plants and its implications for vegetarians (see also this article from December 2009 and this one from March 2011).

I often hear vegetarians dismiss this argument as a disingenuous display of concern for plants, but I think there’s a bit more to it than that, at least when the argument is made well. Some animal rightists argue that killing animals is incompatible with generally accepted ethical principles. The “right” way to make the “plants like to live” argument is to argue that the very same line of reasoning amounts to an argument against eating plants. If the argument could be made soundly, it would present a problem for the argument against eating animals–unless the person making it were also willing to give up eating plants. The point is that an argument based on a need to be logically consistent doesn’t deserve to be taken seriously if it isn’t itself logically consistent. This an instance of the reductio ad absurdum, which I’ve written about in another context. Such an argument, it should be noted, has nothing to do with whether the person making the argument cares about plants or animals, and everything to do with proving that an argument fails to meet its own standards of consistency.

That said, I believe there are good reasons to give a pig more consideration than a pea plant. More than anything, I see this as an argument that arises from imprecision.

The New York Times piece asks,

Is it morally permissible to submit to total instrumentalization living beings that, though they do not have a central nervous system, are capable of basic learning and communication? Should their swift response to stress leave us coldly indifferent, while animal suffering provokes intense feelings of pity and compassion?

I find myself unmoved by this argument because my “intense feelings of pity and compassion” for animals do not arise from the simple fact of the animals’ capacity for “basic learning and communication” nor from their “swift response to stress.” Such an argument would be even more foolish than the New York Times‘s Michael Marder implies. Indeed one could easily envision computers or robots that had similar traits, but most people’s reasons for not eating these entities are entirely selfish. They probably don’t taste very good, they contain toxic substances, they’re hard to chew, they’re likely to scratch our throats and mouths, and they tend to be a lot more expensive than most foods. I doubt any vegetarian would argue that a computer deserves better than to be eaten.

More broadly, I would reject the idea that the existence of plant survival mechanisms is evidence that plants take an interest in living. Indeed, if one considers the process of natural selection, it shouldn’t be surprising that an organism that’s alive today has mechanisms that have increased its chance of survival. According to the theory of natural selection, those organisms with survival mechanisms should be more likely to have survived. That’s exactly how natural selection works.

The question, then, is what makes animals different? I would argue that the difference lies in the fact that animals tend to respond to stimuli in ways that we can relate to. When we watch a video of a pig writhing at slaughter, it’s easy to believe that we’d react similarly if we were exposed to similar stimuli. Because we associate both the stimulus and the reaction with pain, it’s not unreasonable to guess that the pig is experiencing something similar to what what we know as pain. But that’s not quite enough to draw that conclusion; one could envision a robot programmed to react similarly. The most important piece of information is that science tells us that the pig–unlike a robot–has the capacity to experience pain and suffering similarly to humans. The pig’s suffering is similar in all of those ways to an experience that we want to avoid, but it’s much harder to relate to the pea plant in dry soil. In that respect, I think it’s perfectly reasonable to give the pig more consideration than the pea.

I want to emphasize here that I’m not arguing that an organism should be considered based simply on its overall similarity to humans. Instead, I argue for consideration based on sentience and the interests that arise from it but that sentience can only be meaningfully understood by comparing certain traits (for example, nervous systems and responses to stimuli) to their human counterparts. This means that some traits (e.g. intelligence) are not directly relevant. (If anybody wants to propose an alternative, I’m interested to hear about it in the comments.)

Might this line of reasoning lead to a stronger argument for sparing a pig than, say, a chicken? Perhaps, but the issue is complicated by the fact that it takes many chickens to provide the same amount of meat as a single pig. In any case, I think there’s a good case for giving either more consideration than a pea plant. I’d feel less comfortable saying the same of an ant or an oyster, and that doesn’t particularly bother me.

Inevitably, some will say that this line of reasoning is anthropocentric. Perhaps so, but I don’t see that as much of a criticism at all. Specifically, insofar as it gives precedence to sensations similar to those that we know as humans, I don’t think it’s any more anthropocentric than making decisions based on what we know (and can know) as people. And I much prefer that to the alternative.

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Foods are (relatively) easy to isolate

Michael Pollan explains the problem with nutritionism:

The problem starts with the nutrient. Most nutritional science involves studying one nutrient at a time, a seemingly unavoidable approach that even nutritionists who do it will tell you is deeply flawed. “The problem with nutrient-by-nutrient nutrition science,” points out Marion Nestle, a New York University nutritionist, “is that it takes the nutrient out of the context of the food, the food out of the context of the diet, and the diet out of the context of the lifestyle.”

If nutrition scientists know this, why do they do it anyway? Because a nutrient bias is built into the way science is done. Scientists study variables they can isolate; if they can’t isolate a variable, they won’t be able to tell whether its presence or absence is meaningful. Yet even the simplest food is a hopelessly complicated thing to analyze, a virtual wilderness of chemical compounds, many of which exist in intricate and dynamic relation to one another, and all of which together are in the process of changing from one state to another. (62)

Of all the things I’ve taken issue with in In Defense of Food, this is probably the one that most consistently makes me cringe each time I read it. The problem is that everything Pollan says about the complexity of foods actually works against his thesis. To claim that a food is “a virtual wilderness of chemical compounds, many of which exist in intricate and dynamic relation to one another” is to say that the chemical compounds in foods are difficult to isolate. Foods, by contrast, are relatively easy to isolate because when scientists study the effects of foods as a whole they take a pass on analyzing that “hopelessly complicated thing.”

Pollan continues,

So if you’re a nutrition scientist you do the only thing you can do, given the tools at your disposal: Break the thing down into its component parts and study those one by one, even if that means ignoring subtle interactions and contexts and the fact that the whole may well be more than, or maybe just different from, the sum of its parts. (62)

In reality, nutrition scientists often do study whole foods and broader dietary patterns, which is why Pollan can claim on the very next page that “researchers have long believe that a diet containing lots of fruits and vegetables confers some protection against cancer.” It’s also wrong to say that nutrients can only be studied one by one; Pollan will later tell us about interactions betwen omega-6 and omega-3 fatty acids.

That said, researchers do expend considerable effort with the nutrient-by-nutrient approach, even if not for the reasons that Pollan cites. Frank Hu and Walter Willett of the Harvard School of Public Health justified this choice in a letter (included in Pollan’s references) responding to T. Colin Campbell’s criticism of reductionism:

Although we agree that overall dietary patters are also important in determining disease risk, we believe that identification of associations with individual nutrients should be the first step because it is the specific compounds or groups of compounds that are fundamentally related to the pathophysiology of the disease. Specific components of diet can be modified, and individuals and the food industry are actively doing so. Understanding the health effects of specific dietary changes, which Campbell refers to as “reductionism,” is therefore an important undertaking.

Not being a dietitian or a public health expert, I’m not going to try to evaluate the merits of this argument. What I think is significant here is that Pollan has invented his own dubious argument for focusing on nutrients instead of discussing an argument that researchers actually use. By doing so, not only does he fail to address the real argument, but he also opens the door to a broader dismissal of scientific inquiry on questions of nutrition.

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