In the Wall Street Journal teaser to her new book, "Best Before: The Evolution and Future of Processed Food," Nicola Temple argues (in line with the title the editors gave to her piece) that we should "Give Processed Food a Break."
Nicola gives these examples of relatively innocent food processing. (I numbered the excerpts.):
1. Our earliest ancestors pounded otherwise inedible tubers with rocks and sliced meat with primitive tools—processing methods that are credited with beginning the trend in our evolution toward smaller teeth and jaws and bigger brains. We spend only 5% of our day chewing our food, while our closest primate relatives, chimpanzees, spend 37% of their day that way, according to a 2011 study.
2. The prevalence of diseases related to nutrient deficiency has led to the mandatory fortification of processed foods such as salt and wheat.
3. Now the quest for more sustainable sources of protein and more awareness of animal welfare are driving the effort to develop “clean meat”—lab-cultured protein that doesn’t require the slaughter of animals.
4. ... there’s a nutritional case for frozen food generally over fresh. Vegetables and fruit destined for flash freezing are picked when they’re ripe, while fresh produce is usually picked underripe and artificially ripened closer to the point of sale. Produce starts to degrade the moment it is picked, and the “fresh” peas or tomatoes that have been traveling for a week are often less good for you than their frozen versions.
Finally, one of my daily staples—prewashed lettuce and spinach—depends on some processing. I don't know if I would have the meal-preparation stamina to eat as much lettuce and spinach as I do without this processing:
5. So what explains those lovely packaged, fresh-cut leaves in the supermarket? To limit microbial growth, companies must wash them one or more times with a disinfectant such as a chlorine solution or ozone added to water to label them as pre-washed, according to FDA guidelines. (Even those labeled “unwashed” are washed in water at least once.)
Nicola is certainly right that "food processing" can be either good or bad. But there are three reasons to be suspicious of food processing.
Most Food Processing Makes Food Easier to Eat and Enhances Digestibility. If carbohydrates are too easy to digest, they can cause a blood sugar and insulin spike up, followed by a blood sugar crash which tends to make people hungry again. Things as simple as cooking and juicing can work in this direction:
Cooked carrots cause a much bigger spike up in blood sugar than raw carrots. (See "The Keto Food Pyramid.")
Fruit juice makes insulin spike up more than whole fruit. (See "Forget Calorie Counting; It's the Insulin Index, Stupid.)
More generally, if food becomes easier to eat physically, and instantly ready, you are more likely to eat it when it is otherwise a bad idea to eat it.
The Newer the Type of Food Processing, the Less Tested It Is By Time. There are some silly ideas in the Paleo diet—for example, treating honey as a freebie, when it is unlikely that our distant ancestors got their hands on honey all that often. But I agree with the basic idea that what our ancestors ate has been tested by time in a way newer versions of food haven't been. Human beings are fundamentally omnivores, so a large variety of foods have been well-tested by many, many thousand years worth of consumption experience.
Milk may have only a few thousand years worth of experience of testing behind it and so may be more problematic. (See "Is Milk OK?") And cancer hits preferentially at older ages that people often didn't make it to in any case in the bad old days; so potential problems such as the possibility that meat might contribute to cancer have not have been tested as well by time as one would like. (See "Meat Is Amazingly Nutritious—But Is It Amazingly Nutritious for Cancer Cells, Too?", "How Fasting Can Starve Cancer Cells, While Leaving Normal Cells Unharmed", Why You Should Worry about Cancer Promotion by Diet as Much as You Worry about Cancer Initiation by Carcinogens, and "Good News! Cancer Cells are Metabolically Handicapped.") On a different front, having regular meals has not stood the test of millenia. And there is reason to think the common custom of three meals a day is not that good for us. (See "Stop Counting Calories; It's the Clock that Counts.")
But any likely danger of milk, meat or regular meals pales in comparison with the dangers from newfangled types of food processing that have only affected ordinary people's diets in the last few hundred years. Sugar refining and flour milling are good examples. (See "Diseases of Civilization", "Sugar as a Slow Poison", "The Case Against Sugar: Stephan Guyenet vs. Gary Taubes", The Case Against the Case Against Sugar: Seth Yoder vs. Gary Taubes", and "Gary Taubes Makes His Case to Nick Gillespie: How Big Sugar and a Misguided Government Wrecked the American Diet.")
Types of food processing that came into their own in the 20th century or more recently should also be suspect. Some we know reasonably well to be bad, such as the hydrogenation of oil that put transfats into margarine. But it is the 20th-century and more recent food-processing practices we don't know yet are bad that I am even more worried about. It often takes decades for research to establish that something is bad. And it often takes decades for people to get interested enough in the question of whether something is bad to begin that arduous process of research. For many, many types of food processing, the right view is that we simply don't know if it is safe or not. A particular thing might be fine or it might be terrible. A few decades of experience isn't enough for us to know. I am willing to take my chances with modest amounts of some processed foods that serve important purposes for me personally; basic Ranch dressing and Halo Top ice cream come to mind. But I don't pretend to myself that I know they are altogether safe.
Food Companies Have a Different Objective Function Than You Do—Or at Least a Different Objective Function Than Your Long-Run Self Does. I have saved my biggest concern about food processing for last. With a little bit of exaggeration, I can say that food companies are maximizing against you. What is their objective? They want you to buy a lot of their food. That may involve being able to claim their food is healthy, but typically doesn't involve in any big way actually having the food be healthy. In addition to being able to make claims that their food is healthy, they want to make it tasty, quick and addictive. (To avoid argument, let me define "weakly addictive" as "even when you already have a lot of experience with the food, if you eat one, it will make you want to eat more, as when Lay's bragged about the weakly addictive quality of its potato chips, advertising "bet you can't eat just one.") Food companies also care about your willingness to pay a premium price and keeping the cost per unit down, but getting you to buy a lot of their food is pretty important to their success.
The basic message here is the one George Akerlof and Robert Schiller lay out in Phishing for Phools:
Food companies are not your friend. They are in it for themselves. The more complex the food processing they have done, the more room there is to trick you in some way.
Here let me make an analogy to consumer finance companies. When a financial product is very complex, with lots of fine print, it opens up more ways to trick you. There, the government can help, as I argue in "On the Consumer Financial Protection Bureau." Unfortunately, at this point, the government is much more ignorant about what is safe and unsafe in our diets than it is about what is safe or unsafe in consumer finance. So it is best to stay away from complex processed products as much as possible (or as much as personally tolerable). At a minimum, you should consciously think about how much you trust a particular food company before you eat complex processed food they have created.
Conclusion. Particular types of food processing may be innocent, but in my view, any particular type of food processing should be considered guilty until proven innocent. Some types of food processing have passed such a trial. Many, many haven't.
Don’t miss my other posts on diet and health:
I. The Basics
II. Sugar as a Slow Poison
III. Anti-Cancer Eating
IV. Eating Tips
V. Calories In/Calories Out
VI. Other Health Issues
VIII. Debates about Particular Foods and about Exercise
Julia Belluz and Javier Zarracina: Why You'll Be Disappointed If You Are Exercising to Lose Weight, Explained with 60+ Studies (my retitling of the article this links to)
IX. Gary Taubes
X. Twitter Discussions
XI. On My Interest in Diet and Health
See the last section of "Five Books That Have Changed My Life" and the podcast "Miles Kimball Explains to Tracy Alloway and Joe Weisenthal Why Losing Weight Is Like Defeating Inflation." If you want to know how I got interested in diet and health and fighting obesity and a little more about my own experience with weight gain and weight loss, see “Diana Kimball: Listening Creates Possibilities” and my post "A Barycentric Autobiography. I defend the ability of economists like me to make a contribution to understanding diet and health in “On the Epistemology of Diet and Health: Miles Refuses to `Stay in His Lane’.”