Saturday, May 15, 2010

“Eat food. Not too much. Mostly plants.”

I recently finished In Defense of Food, another engaging piece by Michael Pollan. The focus of the book is nutrition science and it’s unfortunate relationship with the food industry. The first part of the book describes our current state of knowledge and the process of what he refers to as reductionist science. As a scientist, Pollan’s critique made me a little defensive. Reductionist science, the process of studying a system or problem by reducing it to smaller, testable pieces is really just science. That’s how it’s done. When a field is quite young, like nutrition science is, the testable pieces do not constitute a sophisticated understanding of the system as a whole. However, as a field matures, we can test more complex aspects of the system until we arrive at a big picture understanding that includes and identifies the most influential factors. I think Pollan’s point is not that reductionist science is bad, but simply that the field is not mature enough at present that we should rely solely on the results and discoveries of nutrition scientists when making decisions about what and how to eat. The conversation between nutrition scientists and the general public is further complicated by the influence of the food industry.

In an attempt to make their products more desirable to consumers, food marketers often apply health claims to their products. But are those claims justified? They probably are when all of the caveats that come with scientific results are taken into account. Unfortunately, that can make for a rather long and potentially confusing label rather than a colorful banner enclosing a catchy phrase. A hard look at the literature and discussions with several prominent nutrition scientists offered Pollan very few certainties about what we humans ought to eat to be healthy. In fact, the only consensus opinion was to eat more fresh fruits and vegetables, advice which is largely absent from food advertising. The lack of certainty about what we should eat is surprising considering all of the diet books and food fads we constantly hear about. Listen to any TV commercial for a food product or weight loss plan and you are likely to hear words like high fiber, low carb, low fat, probiotic, low glycemic index, or antioxidant. All these words are supposedly linked to health benefits and perhaps they are healthy attributes. The trouble is, because of our incomplete understanding of nutrition, we may be substituting away from healthy foods in our quest to get more or less of a certain attribute, which itself only might be better for us given several caveats. In the worst cases, such as substituting margarine for butter to avoid cholesterol and saturated fat, we end up getting far more dangerous substances instead – in that case, trans fat.

Given the uncertainties about nutrition and health, it seems like the health claims on some food products border on false advertising. The waters have been further muddied with the advent of qualified health statements, a category introduced by the FDA in 2002. As an example, Pollan quotes the FDA-approved qualified health statement for corn oil, not a substance usually considered healthy. “Very limited and preliminary scientific evidence suggests that eating about one tablespoon (16 grams) of corn oil daily may reduce the risk of heart disease due to the unsaturated fat content in corn oil”. It’s already not a particularly strong statement, and still requires the qualifying statements that the “FDA concludes that there is little scientific evidence supporting this claim” and “To achieve this possible benefit, corn oil is to replace a similar amount of saturated fat and not increase the total number of calories you eat in a day”.

Now it’s not clear that this health statement has any value at all, and yet, it allows Frito-Lay to claim their chips are heart healthy due to their use of corn oil in chip production. Remember that in order for these chips to offer your heart anything at all, you would need to first determine how much corn oil is in each chip, how much saturated fat you are replacing by eating the corn oil in the chips instead of some other food, and the number of calories you normally eat in a day along with the calories in both the chips and the food you are replacing with chips. This is, of course, totally impractical. Furthermore, the appearance of a heart healthy label is much more likely to induce people to simply eat more of that food, which is certainly what Frito-Lay hopes to achieve. How could anyone guess the amount of calculation that would be required to reap the benefits of corn oil, which may not even exist in the first place?

It seems to me that health claims are all but meaningless. There is no way for the average consumer to understand where a health claim comes from or what it really means. Not only may that consumer not benefit as they might expect, they may actually be negatively impacted by consuming this food! A practical solution, Pollan suggests, is to entirely discount health claims on food products and focus on eating whole, unprocessed foods instead. Fresh produce, the only food that nutritionists agree we should eat more of, rarely even has packaging much less health claims. Given the youth of nutrition science and the fact that it’s results are often co-opted and misconstrued by overzealous food marketers, Pollan advises that we use knowledge about what and how to eat that has been passed down to us for generations. He sums up his recommendations with the phrase: "Eat food. Not too much. Mostly plants." Sounds like good advice to me!


  1. This reminds me of my absolute favorite: non-fat cooking spray (ex: Pam). Since the serving size of 1/3g, which is in-fact pure oil, contains less than 0.5g fat, it's technically a non-fat product. Let's all raise our Pam and take a swig.

    Since advertisers will always try to exploit any possible loophole or triviality, (I once bought a bag of non-fat carrots!!) the only real way around this is for people to know [roughly] what they are eating. I've been of the mind that "anything you order is bad for you" as a backup plan. In short, don't expect anyone to really protect you :)

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