Archive for Facts

Some corrections and clarifications

Last Friday, while working on my last entry, I came to the realization that two sentences in my piece in the Berkeley Science Review in September were not quite right. These sentences contained a number of claims which were either subtly wrong, misleading, or which simply could have been expressed more clearly.

The sentences in question came in my response to Michael Pollan’s assertion that “the dietary advice enshrined not only in the McGovern ‘Goals’ but also in the National Academy of Sciences report, the dietary guidelines of the American Heart Association and the American Cancer Society and the U.S. food pyramid bears direct responsibility for creating the public health crisis that now confronts us.” I wrote,

However, McGovern’s Goals called for a substantial reduction in refined carbohydrate consumption and an increase in consumption of carbohydrates from fruits, vegetables, and whole grains. Americans collectively disregarded both of those recommendations, as well as a recommended decrease in daily energy intake.

These sentences have since been corrected. Here’s what I think deserves correction or further explanation (all data on historical consumption of foods are from USDA loss-adjusted food availability data):

  • George McGovern’s Dietary Goals for the United States didn’t directly call for a reduction in consumption of refined carbohydrates (which includes both refined grains and added sugars). The first edition (published in February 1977) called for a forty-percent reduction in sugar consumption. The second edition (published in December of the same year) called for a forty-percent reduction in consumption of refined and processed sugars. This means that it would have been consistent with the advice to replace added sugars with white flour. However, that isn’t what Americans did; they increased their consumption of both refined grains and added sugars. Consumption of added sugars did decrease somewhat as a percentage of total calories after 1977, but not by the 40% recommended by the Goals.
  • The Goals left some ambiguity over whether whole grains should be preferred to refined grains. The document listed among a set of “Changes in Food Selection and Preparation” the recommendation to “[i]ncrease consumption of fruits and vegetables and whole grains.” However, later, under the heading “Guide to increasing complex carbohydrate consumption,” the document noted that “there have been no studies that have found whole wheat flour to be superior nutritionally to white flour when consumed in a normal diet, and surprisingly few studies have even considered the question.”
  • The recommendation regarding total calorie consumption was found only in the second edition of the Goals. Moreover, that edition didn’t tell everybody to reduce calorie consumption. Instead, it made the recommendation to those who were overweight, and advised the general population to “decrease energy intake and increase energy expenditure.” Most likely, if this advice had been followed it would have resulted in a decrease in energy consumption per capita. However, if I were writing the piece today, I probably would have said that Americans “ignored a warning to avoid excessive caloric intake.”
  • Total consumption of fruits and vegetables actually increased slightly in the years after the publication of the McGovern report. However, the percentage of total calories from fruits and vegetables decreased. The Goals typically called for increases or decreases as a percentage of total calorie intake, so I think it is fair to say that the recommendation on fruits and vegetables was not followed. However, the word choice could have been more clear. Unfortunately, I was not able to find data on consumption of whole grains, but consumption of grains increased substantially. (Pollan claims in In Defense of Food that most of the increase was in the form of refined grains.)

While I should have been far more careful in writing these two sentences, I think that the point I was attempting to make was sound. Namely, considering that substantial parts of the dietary guidelines were not followed, it doesn’t make sense to blame the guidelines for health problems that have resulted. That said, it’s important to get the details right, and I should have been more careful. I’ll try harder to do both of those in the future.


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Diet, Nutrition, Cancer, and Sloppy Journalism

Michael Pollan argues in In Defense of Food that the Dietary Goals for the United States, compiled by Senator George McGovern’s Senate Select Committee on Nutrition and Human Needs, ushered in an era in which dietary guidelines focused on nutrients to the exclusion of whole foods. He explains that McGovern’s committee initially recommended a reduction in red meat and dairy consumption before the interested lobbies complained. The result was a compromise, urging Americans to “choose meats, poultry, and fish that will reduce saturated fat intake.”

Pollan explains the significance of the change,

First, notice that the stark message to “eat less” of a particular food–in this case meat–had been deep-sixed; don’t look for it ever again in any official U.S. government dietary pronouncement. (24)

As evidence of this last point, Pollan trots out the National Academy of Sciences’ 1982 report Diet, Nutrition, and Cancer. He tells us,

The lesson of the McGovern fiasco was quickly absorbed by all who would pronounce on the American diet. When a few years later the National Academy of Sciences looked into the question of diet and cancer, it was careful to frame its recommendations nutrient by nutrient rather than food by food, to avoid offending any powerful interests. (25)

He further notes, “With each of its chapters focused on a single nutrient, the final draft of the National Academy of Sciences report, Diet, Nutrition and Cancer framed its recommendations in terms of saturated fats and antioxidants rather than beef and broccoli” (26).

After a few minutes of skimming the report, I couldn’t help but wonder whether Pollan and I had looked at the same document. He is correct to point out that the recommendations referenced fat, rather than meat. He’s not quite correct to say that each chapter focuses on a single nutrient. Some of the chapters discuss multiple nutrients (for instance, Chapter 10, titled “Minerals,” discusses selenium, zinc, iron, copper, iodine, molybdenum, cadmium, arsenic and lead), but on that point he’s close enough for me.

Where Pollan misses the mark badly is in failing to note that the report’s recommendations weren’t found in these nutrient-focused chapters. These chapters summarized the existing science on the various nutrients, without saying what we should do about it. The report did include a section called “Interim Dietary Guidelines,” but this was found in the report’s Executive Summary. Summarized, the guidelines were as follows:

  1. “The Committee recommends that the consumption of both saturated and unsaturated fats be reduced in the average U.S. diet.”
  2. “The committee emphasizes the importance of including fruits, vegetables, and whole grain cereal products in the daily diet…Results of laboratory experiments have supported these findings in tests of individual nutritive and nonnutritive constituents of fruits (especially citrus fruits) and vegetables (especially carotene-rich and cruciferous vegetables).”
  3. “[T]he committee recommends that the consumption of food preserved by salt-curing (including salt-pickling) or smoking be minimized.”
  4. “The committee recommends that efforts continue to be made to minimize contamination of foods with carcinogens from any source. Where such contaminants are unavoidable, permissible levels should continue to be established and food supply monitored to assure that such levels are not exceeded. Furthermore, intentional additives (direct and indirect) should continue to be evaluated for carcinogenic activity before they are approved for use in the food supply.”
  5. “The committee suggests that further efforts be made to identify mutagens in food and to expedite testing for their carcinogenicity. Where feasible and prudent, mutagens should be removed or their concentration minimized when this can be accomplished without jeopardizing the nutritive value of foods or introducing other potentially hazardous substances into the diet.”
  6. “[T]he committee recommends that if alcoholic beverages are consumed, it be done in moderation.”

Thus, of the six interim guidelines, only one was expressed in terms of nutrients, two phrased their recommendations in terms of foods (one of those even recommended eating less of something!), two were seemingly commonsense encouragements to keep dangerous substances out of the food supply, and one was a reminder not to drink too much.

Although the recommendation pertaining to vegetables did briefly mention carotenes, the committee included a clarification between the second and third guidelines:

These recommendations apply only to foods as sources of nutrients–not to dietary supplements of individual nutrients. The vast literature examined in this report focuses on the relationship between the consumption of foods and the incidence of cancer in human populations. In contrast there, is very little information on the effects of various levels of individual nutrients on the risk of cancer in humans. Therefore, the committee is unable to predict the health effects of high and potentially toxic doses of isolated nutrients consumed in the form of supplements.

They were serious about this point, too. In his critique of reductionism (which Pollan quotes), T. Colin Campbell (a co-author of the report) wrote that the Federal Trade Commission sued General Nutrition Centers for using the report’s guidelines to advertise supplements.

Although Pollan has argued that nutrition science “knows much less than it cares to admit” (14), the report shows that the science admits its limits more than Pollan cares to admit. The lack of recommendations on so many of the nutrients considered is an implicit acknowledgment of the lack of evidence. Reading the chapters focusing on the various nutrients, one sees the point made more explicitly. For instance, the researchers wrote in the conclusion of their section on selenium, “firm conclusions cannot be drawn on the basis of the present limited evidence.”

As for those chapters on nutrients, one finds plenty of references to whole foods there, too. For instance, though Pollan writes, “The language of the final report highlighted the benefits of the antioxidants in vegetables rather than the vegetables themselves” (26), the report’s summary of the epidemiological evidence on vitamin A reads,

A growing accumulation of epidemiological evidence indicates that there is an inverse relationship between the risk of cancer and consumption of foods containing vitamin A (e.g., liver) or its precursors (e.g., some carotenoids in dark green and deep yellow vegetables). Most of the data, however, do not show whether the effects are due to carotenoids, to vitamin A itself, or to some other constituents of these foods.

Of course, none of this is directly relevant to the question of how much we can learn about human nutrition by studying nutrients (instead of foods), and it’s on that question that Pollan seems to make his main argument. However, what we can observe here is a pattern of misrepresenting the claims that science has made. This, of course, is helpful to somebody trying to discredit a scientific discipline. But it should be much less helpful if Pollan wants to convince the reader that he is a careful researcher and a credible source of information.

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Ask Michael Pollan

To go with this week’s Food and Drink Issue, the New York Times Magazine is running an “Ask Michael Pollan” feature. I’d explain more, but it’s pretty much exactly what it sounds like. Here’s the question I submitted:

In “The Omnivore’s Dilemma,” you marvel at the brilliance of Joel Salatin’s animal polyculture farm, which seems to neatly solve so many of the problems of industrial agriculture. For example, you write, “The chief reason Polyface Farm is completely self-sufficient in nitrogen is that a chicken, defecating copiously, pays a visit to virtually every square foot of it at several points during the season.” This obscures a very important point: chickens don’t fix nitrogen. The nitrogen in the chicken manure is imported in the form of corn, soy, and oats fed to the chickens; Polyface Farm isn’t self-sufficient in nitrogen at all. Earlier this year, Joel Salatin even told an audience at UC Berkeley that he doesn’t describe his farm as sustainable precisely because of the chicken feed. Is it fair to ask how much of today’s alternative food, particularly meat, can reasonably be called “sustainable”? Should the food movement be doing less to glorify meat from small farms and more to help people find satisfying plant-based meals?

Bizarrely, the last few words of the question were edited to read “a satisfying Plan B?” My guess is that a spellchecker was involved. I submitted a similar question with a note of explanation, so I’m hoping this will be fixed.

If you want Pollan to answer my question, you can vote for it by following the link and clicking on the upward-pointing thumb next to my question (login required). Unfortunately, I can’t link directly to the question, so use Control+F (Command+F on a Mac) to find it within the page.

(Updated 10/2/2011 at 9:33PM to clarify the last paragraph, as per Joseph Dowd’s suggestion in the comments.)

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Fact-checking Michael Pollan in Fresh

I’m sitting now watching a screening of Fresh. Michael Pollan has come on screen with some of the same points I’ve already responded to. To name a few:

  • He says that monocultures are bad without mentioning the corn, soy, and oats that feed the chickens and pig on Polyface Farm, his model of polyculture (featured prominently in the film).
  • He repeats the myth that E. coli O157:H7 is a feedlot disease.
  • He correctly points out that feedlots have created waste removal and fertility problems, but then goes on to say that animals make nutrients for plants. As I have mentioned, the nutrients in animal manure come from their feed.

Incidentally, I’m working on a post related to Michael Pollan’s piece in Sunday’s New York Times. I hope to have that up in the next few days.

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The Omnivore’s Dilemma: My Review

When I read Michael Pollan’s The Omnivore’s Dilemma for the first time two summers ago, I was taken aback by a relatively innocent passage in his section on the Supermarket Pastoral food chain:

Taken as a whole, the story on offer in Whole Foods is a pastoral narrative in which farm animals live much as they did in the books we read as children, and our fruits and vegetables grow on well-composted soils on small farms much like Joel Salatin’s. “Organic” on the label conjures up a rich narrative, even if it is the consumer who fills in most of the details, supplying the hero (American Family Farmer), the villain (Agribusinessman), and the literary genre, which I’ve come to think of as Supermarket Pastoral. By now we may know better than to believe this too simple story, but not much better, and the grocery store poets do everything they can to encourage us in our willing suspension of disbelief. (137)

I had certainly never looked at organic food this way. I grew up eating organic food, my parents having discovered organics several years before the US Department of Agriculture began its certification program. When I asked what this word “organic” meant, my mother told me very simply that it meant the food was grown without pesticides. Over the years, I had to tweak that definition for such considerations as chemical fertilizer, but that was pretty much what I thought of when I saw foods labeled organic. I saw no “rich narrative,” no “well-composted soils on small farms,” and no heroes or villains. Nor did I see any reason to be surprised (as Pollan was) by a microwaveable organic TV dinner. That’s not to say that I was born with a detailed understanding of the workings of organic farming. I knew next to nothing about farming, but I never saw any reason to fill in the blanks with these kinds of stories.

I suspect that Pollan is right that Whole Foods would like us to think of these stories. Regardless, I’d venture to guess that he and I experience shopping at Whole Foods about as differently as two people might experience the same grocery store, given his fascination with stories and my own devout literalism.

Having been through The Omnivore’s Dilemma two more times since my initial reading, I’ve come to believe that Pollan’s passion for stories explains a lot about the book. For one thing, it does much to explain the book’s popular success. Not only does Pollan like stories, but he’s good at telling them. In naming The Omnivore’s Dilemma one of the ten best books of 2006, the New York Times called Pollan “the perfect tour guide,” praising his writing as “incisive and alive.” Even B.R. Myers of The Atlantic, in a review that condemned the work as “a record of the gourmet’s ongoing failure to think in moral terms,” conceded that “Pollan writes of the role of corn in American life in such an improbably thrilling manner that I have to recommend the book.”

At the same time, his fixation with stories helps to explain why the book troubles me in some ways. In The Omnivore’s Dilemma, stories aren’t just a way to communicate facts while keeping the reader engaged. One might even say that the facts are secondary to the stories. Rather than base stories on the facts, Pollan chooses stories to fit an overarching reactionary thesis: The best way to eat is following nature and tradition, and our attempts at progress only make things worse. The facts, then, are worked into his narratives, but sometimes they don’t really fit.

Science is one victim of Pollan’s reactionary thesis. Nutritional science receives part of the blame for America’s health problems. “We place our faith in science to sort out for us what culture once did with rather more success” (303), he writes. Yet much of his evidence that “we place our faith in science” lies in our susceptibility to weight-loss diets and food fads that aren’t supported by scientific consensus. Moreover, he seems oblivious to the successes of nutritional science in curing nutrient deficiencies, some of which existed in traditional diets. (To be fair, I do recall Pollan devoting an entire sentence to this point in In Defense of Food.)

Science also receives unfair treatment in the agricultural context. Pollan attempts to summarize parts of Sir Albert Howard’s An Agricultural Testament, which he calls the organic movement’s bible. Yet he makes Howard’s work out to be some sort of anti-science treatise, when it just isn’t. Pollan concludes from Howard’s treatment of humus, “To reduce such a vast biological complexity to [nitrogen, phosphorous, and potassium] represented the scientific method at its reductionist worst” (147). While Howard offers plenty of criticism of modern agricultural science in particular, he does not criticize the scientific method more broadly. Indeed, he even calls aspects of conventional agriculture unscientific, proposes a few scientific experiments, and expresses his hope that science be among the tools of the agricultural investigators of the future. Howard’s work isn’t an argument against science. It’s an argument for better science.

Pollan’s chapters on the fast food chain are probably his strongest, but even there he occasionally oversteps. For example, he suggests that E. coli O157:H7 live only on feedlot cattle, when the scientific literature indicates that this deadly strain of bacteria is about as prevalent in grass-fed cattle. Later, he goes on to include one of the active ingredients in baking powder on a list of “quasiedible substances ” (113), apparently because of its chemical name. In both of these instances, he criticizes something new — feedlots in the first and baking powder in the second — with the effect of making something traditional seem more appealing.

The primary beneficiary of the reactionary narrative is the pastoral food chain, as represented by Joel Salatin’s Polyface Farm. Even as Salatin describes his farm is a “postindustrial enterprise” (191), he explains that in some sense his farming methods aren’t really new at all; they imitate the ecological relationships that exist in nature. To Pollan the farm is “a scene of almost classic pastoral beauty” (124). Its product, he says, “looks an awful lot like the proverbially unattainable free lunch” (127).

Pollan credits Salatin’s farming methods with revitalizing Polyface’s soil without chemical fertilizers. In particular, he writes,

The chief reason Polyface Farm is completely self-sufficient in nitrogen is that a chicken, defecating copiously, pays a visit to virtually every square foot of it at several points during the season. (210)

It’s hard to tell whether he grasps the fact that the nitrogen in the chickens’ feces comes from the food they eat, eighty percent of which is grain-based feed from off the farm. What is certain, though, is that he doesn’t raise the question of what is happening to the land where that feed is grown. We would expect from the earlier chapters that the corn and soy in the feed was grown on a farm that was less classic, less pastoral, and less beautiful than Polyface, so it’s striking that Pollan should choose not to look further. He also doesn’t bother to discuss the question of whether that feed grain might be more efficiently used to feed people directly. Either of these questions would be raised in a more fact-driven work, but there’s simply no room for them in The Omnivore’s Dilemma, as the answers might not fit the thesis.  (Of course, when Pollan later mentions “a denial of reality that can be its own form of hubris” (361), he’s talking about the vegetarians.)

As for the chickens, Pollan buys into Salatin’s argument that they are a purely artisanal product. He doesn’t mention that they are the same Cornish Cross hens that in the context of his Whole Foods meal represented “the pinnacle of industrial chicken breeding,” and which “grow so rapidly…that their poor legs cannot keep pace” (171).

Pollan also points out that Salatin’s pastures remove carbon dioxide from the atmosphere. There’s no mention, however, of the carbon dioxide emissions resulting from Salatin’s hugely inefficient distribution system, which involves large numbers of cars traveling long distances to the farm. (This omission comes even after he’s told us about the fossil fuels used to transport his industrial organic fruits and vegetables from distant farms.) When Pollan tells us that one customer drives 150 miles each way to the farm, it’s merely to be taken as proof of the quality of Polyface meats. There’s no mention of any environmental impact.

Where Pollan’s dedication to his reactionary thesis is perhaps most obvious is in his discussion of vegetarianism. For although there are prominent conservative vegetarians (Matthew Scully among them), vegetarianism today is rooted in a progressive idea. It requires us to accept that we can do something, namely eat, better than our ancestors did it. Indeed, Pollan writes,

Vegetarianism is more popular than it has ever been, and animal rights, the fringiest of fringe movements until just a few years ago, is rapidly finding its way into the cultural mainstream. I’m not completely sure why this should be happening now, given that humans have been eating animals for tens of thousands of years without too much ethical heartburn. (305)

Vegetarianism is something new, and his preferred hypothesis for its recent success is the weakening of our traditions:

But it could also be that the cultural norms and rituals that used to allow people to eat meat without agonizing about it have broken down for other reasons. Perhaps as the sway of tradition in our eating decisions weakens, habits we once took for granted are thrown up in the air, where they’re more easily buffeted by the force of a strong idea or the breeze of fashion. (306)

Being something new and representing a challenge to age-old traditions, vegetarianism simply doesn’t fit with Pollan’s reactionary message. In the reactionary view, it doesn’t make much more sense than high-fructose corn syrup or factory farms. As such, it doesn’t receive serious consideration.

Even before his section on the ethics of eating animals, there are signs that he won’t take his debate seriously. He tells us, for example, that his friends’ son is “fifteen and currently a vegetarian” (271), as though vegetarianism is merely a teenage phase. He also makes no secret of the fact that he’s already made the decision to go hunting even before tackling the ethical issues associated with eating animals.

Pollan gives up meat for a while, inspired by an argument of Peter Singer: “No one in the habit of eating an animal can be completely without bias in judging whether the conditions in which that animal is reared cause suffering” (312). Yet he identifies himself as “a reluctant and, I fervently hoped, temporary vegetarian” (313), so it’s not at all clear that the experiment does anything to lessen his bias.

As a vegetarian, Pollan struggles with the social ramifications of eating differently. He points out that “my new dietary restrictions throw a big wrench into the basic host-guest relationship” (313) and decides, “I’m inclined to agree with the French, who gaze upon any personal dietary prohibition as bad manners” (313). Yet he’ll find himself able to justify only a very limited kind of meat-eating, which likewise represents a “personal dietary prohibition.” He then proceeds to discuss his alienation from traditions like the Passover brisket, apparently not allowing for the possibility that traditions might evolve over time. This rigid view of tradition is an odd one considering his plans to hunt an unkosher pig.

Pollan then moves on to a discussion of animal rights philosophy. He claims to be debating Peter Singer, but he’ll quote Matthew Scully when it better suits his point, never acknowledging any significant difference between the writers. Other times, he’ll just quote Singer out of context.

Pollan eventually argues for meat-eating on the grounds that it serves the interests of domesticated species, which would cease to exist if people didn’t eat them. He doesn’t do much in the way of building up the argument, only hinting at how the interest of a species might be defined and not even beginning to explain why such an interest is more important than the individuals.

Instead of building that argument, Pollan relays a story intended to show that animal activists are out of touch with nature. As Pollan tells it, The Nature Conservancy and the National Park Service need to kill feral pigs to save Santa Cruz Island’s endangered fox, and the animal rights and welfare people oppose the plan out of a single-minded concern for animal welfare. However, the very same Humane Society op-ed that Pollan cites to prove this point actually includes a substantive discussion of the project’s ecological goals. Moreover, Pollan does not address any of the more scholarly objections to the project, such as Jo-Ann Shelton’s argument that the restoration of Santa Cruz Island is motivated by human interest.

Pollan then launches into a section called “The Vegan Utopia,” where he points out practical difficulties of a vegan world. First, he reminds us that harvesting grains kills animals. It’s a true statement that people who care about animals should keep in mind, but Pollan goes on to suggest that we would minimize animal deaths by basing our diets on large ruminants. That claim is an apparent reference to a study that was quickly debunked. He then argues that a vegan world would force places like New England to import all of their food from distant places. It’s a dubious claim in view of existing production of soy, wheat, and vegetables in New England. He even goes so far as to suggest that the vegan food chain would be more dependent on fossil fuels and chemical fertilizers than our current food system. Thanks to the inefficiency of feeding grain to animals, that claim is almost certainly false.

As Myers has pointed out, Pollan does not mention a single thing he ate in his time as a vegetarian. Over the course of the book, Pollan describes at least ten meat-based meals, four of those in exquisite detail, so it’s telling that he doesn’t consider vegetarian cuisine to be worth writing about.

Pollan goes hunting, shoots his sow, and even enjoys the experience. Yet when he finds himself disgusted by the sights and smells of cleaning the pig, Pollan can’t help but take one more jab at vegetarians. He expresses pity for the “tofu eater” for his “dreams of innocence” (361), seemingly rejecting the idea that we should even try to do better.

In spite of all these points of contention, I should acknowledge that Pollan gets plenty right in the book. There’s a lot that’s wrong with modern industrial food production. Making bad changes to our food supply has had profound negative consequences for the environment, public health, and animal welfare. On these topics, Pollan can remain faithful to his reactionary thesis while still representing the facts reasonably well. And so a reader learns about things like the psychology of supersizing, the environmental toll of growing corn to feed ruminants, and the miserable life of a battery-caged layer hen.

I suspect that many people find the information about industrial animal agriculture more powerful because they come from an author who so roundly rejects vegetarianism. After relaying the horrors of forced-molting and cannibalism in battery cages, Pollan writes,

I know, simply reciting these facts, most of which are drawn from poultry trade magazines, makes me sound like one of the animal people, doesn’t it? I don’t mean to (remember, I got into this vegetarian deal assuming I could go on eating eggs), but this is what can happen to you when…you look. (318)

It’s much harder for a reader to dismiss a message as the sentimental ramblings of one of the “animal people” when it’s coming from somebody who enjoys beating up on vegetarians.

In this way, The Omnivore’s Dilemma is a book that bring awareness about important issues to a wide audience. The fact of it being such an enjoyable read further expands that audience. However, it should be at most a starting point for those learning about where their food comes from because the underlying reactionary premise sometimes leads Pollan astray. We live in a world that is increasingly unnatural and unlike the one that shaped our cultural traditions. Our population is growing, our planet is warming, and our values and lifestyles have evolved. It doesn’t make sense for our food chain to remain in the past. As innovations like battery cages and high-fructose corn syrup show, not all ideas are good ones, but that shouldn’t stop us from trying to make progress. The future will present us with new challenges, and we’d do well to keep an open mind to new solutions.

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The free lunch

I had hoped to be posting my review of The Omnivore’s Dilemma by now, but I’ve been a bit sidetracked by a calculation that’s just been begging to be done.

Michael Pollan writes that Polyface Farm produces what looks “an awful lot like the proverbially unattainable free lunch” (127). I’ve pointed out before that Polyface does use feed grains from other farms. What I want to look at is how Polyface’s animal product output might compare to using those grains to feed people. Because of the quality of the data, this calculation will unfortunately be only back-of-the-envelope quality, but I hope that it will still have some value.

I’ll first look at the grain used to feed Salatin’s broilers. The most recent printing of The Omnivore’s Dilemma states (page 222) that Salatin raises 12,000 broilers each year. (The productivity numbers in earlier printings were different. In fact, my copy even has different numbers in two different places.) According to Salatin’s Pastured Poultry Profit$, the broilers have a carcass weight of 4 pounds, and the chickens require 3 pounds of feed for each pound of carcass weight (page 185). That comes out to 144,000 pounds of feed each year. Salatin writes that he uses a feed consisting of 52% corn, 29% roasted soybeans, 11% crimped oats, and the rest consisting of fish meal, kelp and nutritional supplements. Since I’d like my estimate of the energy content of the feed to be conservative, I’ll ignore the calorie content of everything but the grains. Unfortunately, I wasn’t able to find good data for calorie content of feed grains, so I’ll be using data for food-grade grains. Using USDA data for corn, soy, and oats, one finds that a mixture of 0.52 pounds of corn, 0.29 pounds of soybeans, and 0.11 pounds of oats contains a little over 1700 calories. That comes out to 244,800,000 calories in the feed grain.

Now what about the productivity of Salatin’s farm? Here things get pretty tricky. There are several different kinds of animals, and each has several different kinds of meat with different calorie densities. For rabbits, I wasn’t able to find any useful data on carcass weights. Regardless, here is the calculation in tabular form. (References are at the end of the post. Where no reference is given, the source is the version of The Omnivore’s Dilemma available on Google Books.)

Food Quantity Energy density Total Energy (Cal)
Beef 25,000 lb 1163 Cal/lb 1 29,075,000
Pork 50,000 lb 1062 Cal/lb 1 53,100,100
Broiler hens 48,000 lb 2 615 Cal/lb 1 29,540,136
Stewing hens 2,400 lb 3 615 Cal/lb 4 1,476,000
Turkeys 12,000 lb5 541 Cal/lb 1 6,492,000
Rabbits 5,000 lb 6 617 Cal/lb 7 3,085,000
Eggs 360,000 eggs 135 Cal/egg 8 48,600,000
Total 171,368,236

With these very rough estimates, it appears that Polyface actually requires more calories in feed than it produces in food. As I’ve said, these estimates could be off, but I’ve tried to choose them to be favorable to Polyface. For the output, I’ve used energy data from David and Marcia H. Pimentel, which seems to be higher than USDA data for lean meats. (Pastured meat advocates like to say that grass-fed meat is lower in fat than grain-fed meat.) Also, I haven’t even attempted to consider grains fed to the turkeys, the pigs, or the layer hens, but this is likely substantial as well.

If it were the case that there were more energy in the feed grain than in the farm’s output, that would considerably weaken the environmental case for eating meat from a place like Polyface. While I’m still inclined to believe that Polyface meat is far better than factory-farmed meat, Pollan would have us believe that it’s environmentally better to eat Polyface meat than to eat grains because Polyface’s pastures capture solar energy that we wouldn’t otherwise be able to use. That would not make so much sense, though, if Polyface didn’t actually decrease the amount of grain we needed to grow.

One might argue that because Salatin’s cattle don’t eat grain, Polyface grass-fed beef is still relatively low input. But Pollan has made it very clear that each animal has important roles on the farm. The chickens, in particular, are responsible for fertilizing the pasture. Without the chickens and their feed, some other form of fertility would need to be imported from off the farm.

Because I’ve only done a rough calculation, I’m willing to believe that a more careful calculation might show that Polyface actually does produce more calories in food than it requires in grain feed. I welcome any efforts to tear this analysis apart or explain why it is irrelevant. Nonetheless, I think this rough calculation suggests, at least, that the Polyface meal is further from the “proverbially unattainable free lunch” than Pollan has told us. The question remaining is whether it is further from the free lunch than a plant-based meal.


1 David Pimentel and Marcia H. Pimentel. Food, Energy, and Society, Third Edition. Page 70, Table 8.3.
2 Based on 12,000 broilers (as stated in The Omnivore’s Dilemma) with carcass weight of 4 pounds (as stated in Pastured Poultry Profit$).
3 Based on 800 stewing hens (as stated in The Omnivore’s Dilemma) with carcass weight of 3 pounds (as stated in Pastured Poultry Profit$).
4 Unfortunately, I was not able to find a figure for the energy density of stewing hen meat, so I have assumed that it is the same as broiler hen meat.
5 Based on 800 turkeys (as stated in The Omnivore’s Dilemma) with carcass weight of 15 pounds (as stated in Pastured Poultry Profit$).
6 Here, I’ve had significant difficulty finding data. Pollan tells us that Polyface raises 500 rabbits. I’ve assumed a live weight at slaughter of 20 pounds because that seems very large. I’ve also taken into account that dressed weight is typically about 50% of live weight.
7 Based on USDA data for a composite of cuts.
8 This is another somewhat arbitrary number. I’ve chosen this number to be 150% of the USDA figure for a jumbo egg since Polyface eggs are supposedly richer than most.

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Fossil fuels, chemical fertilizers, and farm animals

Michael Pollan moves on from his brief discussion of wild animal deaths on farms to point out certain environmental challenges of a vegan world. He argues,

The vegan Utopia would also condemn people in many parts of the country to importing all their food from distant places. In New England, for example, the hilliness of the land and rockiness of the soil has dictated an agriculture based on grass and animals since the time of the Puritans. (326)

New England has left the time of the Puritans, however. Tofu and soymilk from Vermont-grown soybeans can now be found in some New England grocery stores. Production of wheat in New England has also increased recently. Maine-based farmer Eliot Coleman has written numerous books on growing organic fruits and vegetables in places like New England. (The page of Coleman’s latest book, The Winter Harvest Handbook, includes a glowing endorsement from Michael Pollan, so perhaps this claim will be updated in the next edition of The Omnivore’s Dilemma).

Pollan continues,

To give up eating animals is to give up on these places as human habitat, unless of course we are willing to make complete our dependence on a highly industrialized national food chain. That food chain would be in turn even more dependent than it already is on fossil fuels and chemical fertilizer, since food would need to travel even farther and fertility — in the form of manures — would be in short supply. (326)

This is a very bold claim. Pollan isn’t merely saying that the most sustainable agriculture would include some farms like Polyface Farm. He’s suggesting that we’d use more fossil fuels and chemical fertilizers with a vegan food system than we do now by feeding grain to cattle. (Update: Commenter Eric B argues that this isn’t what Pollan is saying.)

Even if we accept the premise that food would need to travel significantly farther in a vegan world, Pollan is wrong to say we’d need more fossil fuels. Any increase in fossil fuels use for transportation would easily be offset by reduced production energy. In their book Food, Energy, and Society, David Pimentel and Marcia H. Pimentel (whom Pollan cites for much of his data on energy use in the food supply) estimate that producing food for a vegan diet requires about 18,000 kilocalories of fossil fuel energy per day, compared to 35,000 kilocalories for a nonvegetarian diet (Figure 11.1, page 134). They also estimate (page 258) that transporting 1 kilogram of food 1,000 kilometers from the farm to cities and towns uses 640 kilocalories of fossil fuel energy. If we combine this with David and Marcia Pimentel’s estimate that Americans consume about 1000 kilograms of food per year (computed for a lactoovovegetarian and nonvegetarian diet, but I doubt that vegan should require much more food mass), it turns out that we’d have to move our vegan food more than 9,600 kilometers to offset the production energy savings the vegan diet offers over the nonvegetarian diet. In other words, even if we ignored the energy used to transport food today, and even if our hypothetical vegan country shipped all of its food 5,600 kilometers from San Diego, California to Calais, Maine, the vegan nation would still be considerably less dependent on fossil fuel energy.

As for chemical fertilizers, I’m not going to do a calculation because numbers are a bit harder to come by here, but I think Pollan has that wrong, too. If we ate our grain instead of feeding it to livestock, we’d need far less of it, and most grain today is grown with chemical fertilizer (as Pollan has told us earlier).

Pollan adds that the vegan world wouldn’t have farm animals to provide manure and tells us, “it is doubtful you can build a genuinely sustainable agriculture without animals to cycle nutrients”  (326), two claims related to issues I’ve addressed before. Pollan hasn’t addressed the fact that the nutrients in manure come from the food that animals eat. Last time I wrote,

[W]hen animal manure is used to fertilize plants, the nitrogen it provides was fixed either [chemically] by the Haber-Bosch process or by nitrogen-fixing bacteria in the roots of plants. Any nitrogen animals leave on the pasture was ingested in their food. This is a point that Pollan seems to miss when he writes,

The chief reason Polyface Farm is completely self-sufficient in nitrogen is that a chicken, defecating copiously, pays a visit to virtually every square foot of it at several points during the season. (210)

Polyface Farm isn’t completely self-sufficient in nitrogen, though. There’s plenty of nitrogen in the eighty percent of the chickens’ diet that Pollan has told us (just a few sentences earlier) comes from  corn and soy that Salatin buys. For the soil to maintain a stable nitrogen level from year to year, it’s necessary for the chicken feed together with the nitrogen-fixing bacteria in the roots of clover  and other legumes to provide enough nitrogen to replenish whatever is removed from the farm in food for humans. Passing through the chickens’ digestive systems doesn’t increase the amount of biologically-available nitrogen in the feed.

The farm where the chicken feed is grown is depleted of nitrogen when the corn and soy are removed to feed Salatin’s chickens. Thus, as I wrote last month, it makes little sense to say that animals “cycle nutrients” on the farm. The word “cycle” suggests that the animals are somehow returning nutrients to the farm. That’s not what animals do. They take nutrients from plants (like grasses) that aren’t directly usable to humans and bring them into our food supply by fertilizing plants we can eat with their manure. Putting animals on the farm doesn’t change the need to replenish the nutrients that are removed in the form of food for humans. Sometimes these nutrients can be replenished naturally, by growing leguminous plants (like clover), but even at Polyface Farm, it’s necessary to import fertility from a neighboring farm in the form of conventionally-grown corn.

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