“Don’t eat processed food!”
This is a common piece of advice for people who want to eat healthier to prevent diet-induced obesity and heart disease. But food scientists understand this advice as an over-simplification of a complicated issue, and we want to help you understand what processed food really is so that you can make more informed decisions in the grocery store.
Processing is any change made to a raw agricultural product after harvest.
Farms produce food, it’s true, but straight from the farm that food is a raw, sometimes inedible product. Although whole fruits and some vegetables can be eaten as-is, most foods are processed before they reach our grocery stores, restaurants, and home kitchens. Processing can be physical, such as sorting, washing, shelling/dehulling, peeling, milling, and chopping; thermal, such as freezing, cooking, drying, sterilizing/retorting, and pasteurizing; chemical, such as fermentation, salting, sweetening, and adding nutrients or preservative compounds; or transformative, whereby multiple ingredients are combined in prepared foods that don’t closely resemble their individual ingredients. (Packaging is also a form of food processing, but won’t factor into this post as much.) Most foods are subjected to several processes in these different categories before consumption. And as the level of processing increases in a food, the convenience of that food also tends to increase.
Before most food processing was done in factories in the developed world, all of this food processing was done by someone—mostly women—in home kitchens. This is really important to remember, because the more you base your diet on minimally processed foods, the more processing you have to do yourself before the food is ready to eat. Today, no one in developed countries needs to mill their own flour, bake their own bread, churn their own butter, culture their own yogurt, boil their own chicken stock, can their own fruits and vegetables, or shell their own fresh peas, unless they want to! Such activities are typically reserved for upscale restaurants and food hobbyists on weekends. As a home cook and food hobbyist myself I spend 1-2 hours each weekday and up to 5 hours each Saturday and Sunday preparing food, but I still rely on basic processed foods like canned tomatoes, beans, and chicken broth, prepared breads and pasta, and milled rice, flour, and starches.
Processing is just a tool, and therefore it can be used for good or for ill, whether in a home kitchen, a restaurant, or a factory. For example:
Processing can degrade nutritional value or create toxins: Most wheat flour and rice are consumed after milling has removed the fibrous, nutrient-filled bran layer. Fruit juice, though still full of vitamins, provides all the sugar of fruit without the fiber that slows down absorption of that sugar into the blood stream. Acrylamide is a possible human carcinogen that is produced when frying potatoes. Nitrites are added to cured meats as preservatives, but are also associated with negative health effects.
Processing can enhance nutritional value and eliminate toxins: Government-mandated fortification of refined flour is credited with greatly reducing neural tube defects in developing infants. Flash-freezing vegetables prevents the loss of nutrients that begins immediately after harvest. Canning tomatoes boosts bio-available lycopene content. Parboiling rice transfers nutrients from the bran and hull into the starchy endosperm so even after milling it retains these vitamins. Treating corn with an alkaline solution makes the essential B3 vitamin niacin bio-available. One of the primary purposes of food processing is preservation by preventing microbial growth, and thermal and chemical processing can also neutralize natural plant toxins (see our video for more info!).
Processing can be used as a vehicle for high loads of sugar, salt, and fat: Some of the most highly processed foods in grocery stores are also nutritionally unbalanced to an extreme degree. Chips, crackers, cookies, candy, sugar-sweetened beverages, boxed prepared foods, and yogurt sweeter than ice cream: these are just a few examples of foods that will give you a lot of Calories without a lot of micronutrients, or fiber to promote healthy digestion. Most of the time when people say you shouldn’t eat processed food, this is what they’re talking about!
Processing can be used to make nutrient-dense foods more convenient and accessible: Canned vegetables, particularly beans and tomatoes, are faster to prepare than their fresh counterparts. Baby carrots, which are really whittled-down version of large carrots, are a great ready-to-eat snack. And by processing fruits and vegetables into more shelf-stable products, we can enjoy year-round variation in our diets.
Why would we ever process foods in ways that lead to nutrient loss or imbalance? The answer to that question comes down to palatability, functionality, and shelf-life. Consumers prefer white rice to brown, and we’ve also developed a strong preference for sweet foods, such that even savory items like jarred tomato sauces and whole-wheat bread contain added sugar to moderate acid and bitter flavors. Processing can also enhance final products; for example, white flour produces softer, more high-rising breads and baked goods, and hydrogenating plant oils prevents unsightly oil separation. Fresh foods spoil quickly, and many processes that strip nutrients also promote better storage, which ultimately reduces food waste. Every process we apply to food has costs and benefits.
Unfortunately, the mentality that processed foods = bad hasn’t given us less processed food as much as it’s given us reformulated processed foods. We eat “multigrain” pasta that still lacks whole-grain nutrition, brightly-colored sugary cereals made with “natural” flavors rather than artificial ones, and fruit snacks made from apple puree concentrate—which looks better on a label than “sugar” even though that’s what it is! These lateral moves in food composition haven’t given us more nutritious options. As long as our diets are primarily composed of high-Calorie, low-nutrient convenience foods, we won’t make meaningful steps to reduce preventable diseases.
From a food scientists’ perspective, the proper response is not to shun all industrially processed foods, abandoning modern life to devote yourself to food preparation. Rather, we need to rely on other criteria—Calories, macronutrient and macronutrient composition, fiber, and servings of fruits of vegetables—to choose the best whole and processed foods for healthy diets.
Eat processed foods, don’t eat the pseudoscience.
Kathryn is a native Texan with a B.S. in Biology from the University of North Texas, and is currently finishing her M.S. in Food Science at the University of Arkansas, where she will be starting a Ph.D. in Plant Science in August! She studies impacts of post-harvest processing on rice quality now, and will be studying the genetic basis of rice quality in the future. She spends way too much time snuggling with her cat, watching Netflix with her husband, and tweeting (@kathrynhaydon!). You wish you could come to her house for dinner tonight, because she’s probably cooking something delicious.