Decoding Food Processing

Food processing is nothing new. It dates back to the prehistoric ages when crude processing included fermenting, sun drying, preserving with salt, and various types of cooking such as roasting, smoking, and steaming. Salt-preservation was especially common for foods that made up warriors' and sailors' diets until the introduction of canning methods. Modern food processing technology in the 19th and 20th centuries was developed in a large part to serve military needs, with the largest boom in highly processed food occurred after World War II, spurred in part by the military's need to transport rations over long distances while increasing their shelf life, palatability, and calorie density.

Processed foods are now a central part of the modern American diet. One study using data from the U.S. National Health and Nutrition Examination Survey found that ultra-processed foods comprised about 60% of total calories in the average American adult's diet. (Among American children, that percentage is closer to 70%.) According to the Department of Agriculture (USDA), processed foods are defined as any agricultural commodities altered from their original state. This includes washing, cleaning, milling, cutting, chopping, heating, pasteurizing, blanching, cooking, canning, freezing, drying, dehydrating, mixing, or packaging. But not all processed foods are created equal. While the term often brings to mind packaged snacks and sugary treats, there are actually different levels of food processing that affect both the nutritional value of what we eat and our long-term health. Understanding the spectrum from unprocessed to ultra-processed foods can help you make informed choices at the grocery store and on your plates.

One popular system to classify processed foods was developed in 2009 by researchers at the University of Sao Paulo, and is called the Nova classification. It describes four categories that consider the degree to which a food is processed and the purpose of these modifications.

1. Unprocessed or Natural Foods: These are foods that come directly from nature and have not been altered. They include fresh fruits and vegetables, whole grains, raw nuts, eggs, fresh meat, and fish. These foods are nutrient-dense and form the foundation of a healthy diet.
2. Minimally Processed Foods: These are natural foods that have been slightly altered for preservation or convenience but retain most of their nutritional properties. Washing, drying, grinding, freezing, or vacuum-sealing are common techniques used in minimal processing. Common examples include frozen vegetables, roasted nuts, dried beans, pasteurized milk, and whole grain flour. Most dieticians include cooking ingredients such as butter and oils in this minimally processed category. These ingredients are not meant to be eaten alone, but rather meant to be added to foods during the meal preparation process.
3. Processed Foods: These foods have been modified with the addition of salt, sugar, oil, or other ingredients to enhance flavor or extend shelf life. Examples include canned beans, canned vegetables, canned fish, most cheeses, salted nuts, and freshly baked bread (like from a local bakery). These foods usually are made from at least 2-3 ingredients and can be readily eaten without further preparation. While processed foods can still be part of a healthy diet, moderation is key due to added sodium or sugars.
4. Ultra-Processed Foods: Also commonly referred to as "highly processed foods," these are foods from the prior group that go beyond the incorporation of salt, sugar, and fat to include artificial colors and flavors, preservatives, thickeners, emulsifiers, bulking agents, gels, and artificial sweeteners. These additional processing ingredients promote shelf stability, preserve and enhance texture, and increase palatability. Examples of these foods include soft drinks, packaged snacks, instant noodles, breakfast cereals, frozen dinners, and most lunch meats. 

Ultra-processed foods are typically high in sugar, unhealthy fats, and sodium. But it isn't just about what is added to the foods; there are also things missing. Dalia Perelman, a research dietitian with Stanford University, said "They tend to be lower in fiber, micronutrients, phytochemicals" (naturally occurring compounds with potential health benefits). Ultra-processed foods are often mass-produced with low-cost ingredients, making them cheap and highly profitable. Perelman added, "It's not like the industry is trying to kill us. They're trying to make food more affordable, more convenient, and tastier." Yet, she notes, dozens of studies have provided evidence suggesting that high ultra-processed food consumption is associated with a range of adverse health outcomes, including obesity, metabolic syndrome, heart disease, cerebrovascular disease, depression, type 2 diabetes, anxiety, cancer, and mortality from all causes.

The degree of processing matters more than the presence of processing itself. Dr. Carlos Monteiro, who helped develop the Nova classification, explains, "Ultra-processed foods are designed to be convenient and hyper-palatable, but they often undermine satiety and encourage overeating." Multiple studies back up his concern. A 2019 randomized controlled trial by the National Institutes of Health (NIH) found that participants consuming ultra-processed diets ate about 500 more calories per day and gained weight compared to those eating minimally processed foods, even when both diets were matched for calories, sugar, fat, and fiber. Dr. Dariush Mozaffarian, a cardiologist and professor at Tufts University, agreed: "It's not just about individual nutrients anymore. The degree of processing impacts how our bodies react to food."

Dr. Neha Sachdev, a family physician and director of clinical engagement and equitable care at the AMA, said, "Ask yourself: What are some small steps you can take to change your habits and follow a healthier diet with less ultra-processed and processed foods? Small changes add up and once you've established one habit, you can work on changing another." Consider healthy swaps, such as whole-grain cereal with no added sugar instead of highly processed, sugary cereals. Or maybe choose whole-grain, high-fiber breads over white bread products. When looking for a healthy snack, reach for fresh fruit or vegetables instead of crackers, potato chips, or processed cookies.

And remember the fewer ingredients, the better. "If you're getting up to 10, 15, 20 ingredients, it's going to be a lot more processed than something that's three or five ingredients," dietician Lindsey Wohlford said. "The best advice is to choose foods that don't have and don't need labels: fresh vegetables, fruit, dried beans, and intact whole grains," said Dr. Stephen Devries, a preventive cardiologist and executive director of the educational nonprofit Gaples Institute in Chicago. "Among packaged foods, focus on those in which a whole food predominates with as few added ingredients as possible." Perelman agreed, adding her own example: "Buy a pasta sauce with simple, recognizable ingredients - tomatoes, olive oil, herbs - and not too much salt."

Registered dietitian Dr. Marion Nestle advised, "If it looks like it was made in a factory, it probably was. Choose foods closer to their natural form whenever possible." Swapping ultra-processed foods for minimally processed or whole options doesn't mean giving up convenience altogether; frozen vegetables, pre-washed greens, canned beans, or canned tuna can all be smart, nutritious staples. The key is recognizing the difference between foods that have been preserved for safety and those engineered for addictive eating. By understanding the spectrum of food processing, you can take small, meaningful steps toward a healthier plate - and a healthier future.