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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3 Comments »

  1. […] enough to point out when a document doesn’t say what Michael Pollan claims it does or make general comments on the nature of scientific inquiry, more nuanced points about the particulars of nutrition science are beyond me. So for the most […]

  2. I’ve been thinking and reading more about the whole “reductionism” issue. It’s worth noting that folks like Pollan, who have a negative or ambivalent attitude toward science, aren’t the only ones perpetuating the idea that science means reductionism.

    Consider the remarks of P.W. Atkins, an eminent chemist and science advocate. In his essay “The Limitless Power of Science” (in Nature’s Imagination, ed. John Cornwell, Oxford UP, 1995, pp. 122-32), Atkins contrasts science with religion in the following terms:

    [In the religious believer’s opinion] religion is the antidote to reductionism. (122)

    An alternative point of view, however, is that religion has had its day and that science, and the tracing of phenomena back to its [sic] atomic roots that epitomizes reductionism, should be regarded as supreme. (122)

    I consider that the survival of religion and the antireductionism that it represents survives merely because it is so deeply ingrained in our cultural attitudes. (123)

    Someone with a fresh mind, one not conditioned by upbringing and environment, would doubtlessly look at science and the powerful reductionism that it inspires as overwhelmingly the better mode of understanding the world. (123)

    Would not that same uncluttered mind also see the attempts to reconcile science and religion by disparaging the reduction of the complex to the simple as attempts guided by muddle-headed sentiment and intellectually dishonest emotion? (123)

    But, the antireductionists will cry, we need to listen to the spirit and that science cannot replace. (123)

    Scientists, with their implicit trust in reductionism, are privileged to be at the summit of knowledge. (123)

    In the first two pages of his essay, Atkins equates (or at least associates) science with reductionism more than 6 times!

    Things get even more interesting when Aktins turns to the origin of the universe. He writes:

    If reductionist science is to be proved omnicompetent it must achieve a complete description […] Moreover, if it is to be honest, it must achieve all this by starting from something without a precursor; that is, it must start from nothing at all. […] I suspect that the only route to knowledge about the structure and properties of the Universe […] is to speculate about the events that preceded the Creation. I see that we shall need to build a model of what was before there was time in a place that was not space, and to explore whether its consequence was creation. (132)

    I’m not sure that the phrase “what was before there was time in a place that was not space” is even logically coherent, but let’s ignore that problem for the moment. Atkins is apparently quite willing to speculate about what happened “before” the Big Bang. Indeed, in another book, The Creation, he does precisely that, speculating about how our space-time continuum might have emerged from nothing. Now, I’m certainly no expert on cosmology, but I think it’s obviously unlikely scientists will ever be able to verify such speculations empirically.

    This is surely strange. If Atkins’s ideas about cosmology are any indication, then he seems to think that reductionism is as important as empirical verification (if not more so) when it comes to science. I always thought that science just meant testing hypotheses (whether reductionist or not) empirically. If a science advocate such as Atkins associates science and reductionism like this, then is it really surprising when antireductionists like Pollan make the mistake of blaming science?

    • Adam Merberg said

      Thanks for the comment, Joseph. Sorry it’s taken me so long to get around to replying. I also haven’t forgotten your other comment about white bread, but I want to do a bit more research before I answer that one.

      To reply to your comment, I don’t really see any contradiction between Atkins’ writing and my criticisms of Pollan. I don’t think reductionism is inherently problematic. I also agree that science tends to inspire some amount of reductionism. That said, reductionism isn’t so much a part of the scientific method as part of how we go about applying the scientific method. That might seem like a pedantic distinction, but the key point is that when we find that if if scientic inquiry leads us astray, we can rethink how we do that reductionism without giving up on the scientific method altogether.

      Of course, the reductionism may be easier for a chemist like Atkins than it is for a biologist or agronomist. There are people now who are interested in “systems biology,” which is an effort to move away from reductionism, though.

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