Sunday, April 6, 2008

Book review: In Defense of Food

Michael Pollan's The Omnivore's Dilemma, which explores the moral, ecological and health impact of the food we choose to eat, was a life-altering book for me. So I was very excited to receive his follow-up book, In Defense of Food as a birthday gift. Unfortunately, as I read the book, I became gradually less thrilled, and now my Pollan-love has abated somewhat. But overall, I think Pollan and I come to the same conclusions, but perhaps for different reasons.

Pollan begins the book with his catchy new mantra: "Eat food. Not too much. Mostly plants" (I haven't seen this on a t-shirt yet, but fear that it is only a matter of time). Most of the first part of the book is devoted to his distinguishing food from what he calls "edible food-like substances," i.e. foods that have been heavily processed. I was with him this far, but he began to lose me with his forays into critique of food science.

Pollan is often sloppy or unclear in his treatment of the subject. On page 69, in talking about the placebo effect, he says "About a third of Americans are what researchers call responders–people who will respond to a treatment or intervention regardless of whether they've actually received it." I cringed when I read this, for several reasons. For one thing, he makes it sound as though responders are a fixed (and apparently highly suggestible) segment of the population that will respond to anything. This is not the case, nor is it the case that people respond equally to all placebos. He unfortunately does not provide a citation for this particular factoid. The book throughout is rather poorly sourced, with only a few of his claims having more than one citation to back them up.

His main critique of nutrition science is that research in that field has focused on the effects of single nutrients. This, he argues, is problematic because we do not eat nutrients, we eat foods with different combinations of nutrients that may interact with one another and thereby affect our health in ways that would not be predicted from single-nutrient studies. This is a fair enough criticism, but uses this argument to basically reject the entire field of nutrition science (except for those studies which back up his conclusions). In rejecting nutrition science as overly reductionist, he also neglects to acknowledge that the most important discoveries of nutrition science and those which have arguably had the greatest health impact were the identification and treatment of diseases resulting from deficiencies of single nutrients, such as scurvy, rickets, and beriberi.

I do agree with Pollan that nutrition science is not sufficiently advanced that we ought to eat food which has been stripped of its nutritional content through processing and then re-fortified with vitamins, or that we can depend on vitamin supplementation to balance out a diet that is not nutritionally sound. But I imagine most nutrition scientists would also agree with this...unless they work for Frito-Lay, maybe.

Interestingly, for all his talk about reductionism, Pollan does seem to be convinced as to the miraculous health properties of one nutrient: omega-3 fatty acids. He does not attempt to address the apparent contradiction between his criticism of studies that look at single nutrients, and his belief in those exact types of studies about omega-3s. He even manages to sneak in a little anti-science jab when he writes "I have been specifically warned by scientists allied with the carbohydrate camp not to 'fall under the spell of the omega-3 cult.' Cult? There is a lot more religion in science than you might expect." Sounds to me like an advanced case of the pot calling the kettle black!

Another of Pollan's main claims is that the "Western" diet is inherently unhealthy (I agree with him here) and that virtually all "traditional" diets are superior in their health effects. Here, he relies heavily on the work of a dentist, Weston Price, who conducted studies in the 1930s of traditional diets and dental health. Pollan acknowledges that Price "could sometimes come across as a bit of a crackpot," but embraces his conclusions nonetheless.

To be fair, he also looks at other studies of traditional diets, in each case finding that people eating the diets their ancestors had consumed over the past several hundred years were healthier than people who had changed their traditional diets. Even the Masai people, whose diet consisted of meat, blood, milk and virtually no plant foods were deemed to be healthier than people eating a modern Western diet. He quotes one nutritionist as saying "Just don't eat anything your Neolithic ancestors wouldn't have recognized and you'll be OK."

The obvious (to me, anyway) problem with this philosophy is that like most Americans, my Neolithic ancestors were scattered (in my case around Europe) and likely ate vastly different diets from one another. If traditional diets are truly healthier, it seems to me that we much accept one of two explanations: either various cultures were able, through trial and error, to develop optimally healthy diets from the available foods over a period of hundreds of years, OR alternatively, people may have genetically adapted to the diets to which they had access over those hundreds of years to get optimum health out of the foods available to them. Neither of these hypotheses is proven, but given the tremendous variation of the content of healthy traditional diets, the latter seems vastly more likely to me.

Pollan does talk about people adapting to their diets a few times, saying, for example, that "our bodies have a long-standing and sustainable relationship to corn that they do not have to high-fructose corn syrup. Such a relationship with corn sytrup might develop someday (as people evolve superhuman insulin systems to cope with regular floods of pure fructose and glucose)." But he never makes the leap to confront the politically incorrect notion that if people have to adapt to their diets over centuries, the ethnically heterogeneous among us might just be screwed.

That being said, while I disagree with some of Pollan's reasoning and analysis, in the end, we pretty much arrive at the same place. I found the dietary principles he espouses at the end of the book to be sound. In fact, in that part of the book, I felt the flame of Pollan-love starting to come back to life. Overall, I think the book is worth a read...with a bit of skepticism reserved.


Anonymous said...

Nice, I agree--the conclusion (eat whole plant foods) I agree with, but much of his reasoning is flawed. He is a writer, not a scientist, and should be honest about where he's weaker instead of pretending to know.

Good point about people from varying ethnic backgrounds--my "people" come from tons of different places, my boyfriend's come from a bunch of other places, and if we had a kid, we'd have half the planet as our ancestry. So...where does that leave us?

Mae Travels said...

For a discussion about native people's genetic adaptation to locally available food, see "Why Some Like it Hot" by G.P.Nabhan -- I'd be interested in your reaction to this.

Cindy said...

I haven't gotten around to reading this one, or "The Omnivore's Dilemma" yet; but I am currently reading Nina Planck's "Real Food" and wonder if you have any opinions on that.

Dr. LaWade said...

I haven't read either the Nabhan book or the Planck one, but they both sound interesting. However, I don't know how many more "book report" posts I'll be doing, as it takes a lot more time to read a whole book than it does to just summarize the literature on a particular topic! However, I will endeavor to overcome my laziness.

Also, Mae, I love your food blog!

Ellen said...

While I agree that Pollan's book has some obvious flaws, I think you're choosing to gloss over some things that contradict your points.

For example, there are numerous places in the book that he clearly states that while he is loathe to do it, sometimes the only way to discuss parts of nutrition are in the reductionist terms he would rather avoid. You make no allowance for the fact that he acknowledges this shortcoming.

In the specific case of Omega-3s, most of his references to them seem to me more observational than any espoused love for Omega-3s. A few even are there solely to point out continued problems with the re-engineerability of processed foods. (As when he wonders how long before Omega-3 capsules will be baked into breads. This sort of sentences is clearly NOT said in an approving way, especially given the rest of the book's adamant refusal to believe there is any good to be found in processing food.)
Additionally, he spends just as much time pointing out that there is probably too much Omega-6 being consumed, and he plainly states that there is always a demonized nutrient and a savior nutrient, with trans fats performing the role of the former at the moment, and Omega-3s shining in the latter. Such a statement seems to be more observational on his part than a tacit reccommendation to get more Omega-3s.

As for the part where he quotes one nutritionist as saying "Just don't eat anything your Neolithic ancestors wouldn't have recognized and you'll be OK" it's pretty apparent that this is supposed to be a light, almost tongue-in-cheek refutation of processed food, more than a literal reccommendation.

I do understand the further points you make with how Neolithic ancestors had a long time to adapt to certain diets. (And Pollan addresses this briefly when he discusses how for a long time, humans were not able to digest milk beyond infancy, and now many can.)

However, it seems this sentence:
"But he never makes the leap to confront the politically incorrect notion that if people have to adapt to their diets over centuries, the ethnically heterogeneous among us might just be screwed."

is just flatly untrue, for he DOES make that leap. He addresses it when he says that the obvious response might be that eventually we'll adapt to a Western diet. But, if we are to do that, we must be prepared to let those whom it sickens die.