You’ve probably heard health experts say that eating whole foods and skipping processed foods is the key to optimal health. For example, a December 2022 study presented a rather scary statistic linking ultra-processed foods to cognitive decline, saying that people who consumed more than 20% of their daily calories from processed foods had lower overall cognitive abilities. The rate of decline is accelerated by 28%, and the rate of cognitive decline is accelerated by 25%. Executive function declined more rapidly than in people who ate less than 20% of their food.

If you’ve ever wondered what “ultra-processed” foods are, you’re not alone.This is a complex topic.

Most foods are at least minimally processed—usually for preservation or safety reasons—so completely avoiding all processed foods is difficult, if not impossible. It’s not necessary either.

Processed foods tend to get a negative reputation, but there are many low-processed foods that are actually good for us. If we think about foods like baby carrots, nuts, chicken and fish, these foods have to be processed in some way, but they only have one ingredient.

At the other end of the spectrum from processed foods are ultra-processed foods, such as frozen meals, donuts, cookies, and candies. These often contain dozens of ingredients, many of which you’ve never heard of and can’t pronounce. These are items that nutritionists recommend limiting.

Still, nutritionists admit that understanding the difference between processed and ultra-processed foods can be difficult. Here are some tips to help you solve these problems.

Most foods are processed, at least somewhat

Almost all foods need to be processed before they can be eaten, so this can be confusing.

The healthfulness of processed foods often depends on other ingredients added during processing, such as sugar or salt. The USDA defines processed foods as foods that have been altered from their natural state. Therefore, it refers to any produce that has been ground, cut, minced, cooked, frozen, dehydrated or canned.

Technically, many of the foods people consider natural are minimally processed, such as frozen fruits or vegetables, or the bags of pre-cut vegetables found in the grocery store.

Processing techniques such as pasteurization, canning or dehydration also make food safer to store and ensure it lasts longer.

How to understand the different kinds of processed foods

Not all processed foods are created equal. One way to account for different levels of processed foods is the NOVA food classification system, developed by researchers at the University of São Paulo in Brazil. The system is divided into four categories:

Group 1: Unprocessed or minimally processed foods. This refers to fruits, vegetables, seeds, eggs, fungi or milk that are eaten in their natural state or have been modified to remove inedible or unwanted parts such as stems or shells. These foods may be dried, filtered, baked, frozen, or packaged to preserve their natural state, store them, or make them more palatable.

Group 2: Processed culinary ingredients. These items are derived from the first group, or nature, and include oil, butter, lard, sugar, and salt. They are usually used in the preparation of Category 1 foods and are rarely eaten on their own.

Group 3: Processed foods. These foods are produced by adding foods such as salt, sugar or oil (Group 2 foods) to Group 1 foods. Examples include pickles, canned fish, cheese, canned fruit or vegetables, bacon or fresh bread. These foods usually retain their basic identity and some of their original characteristics.

Group 4: Ultra-processed foods. These products are produced through industrial processes such as hydrogenation or the addition of emulsifiers, artificial colours, artificial flavors or preservatives. These include deli meats, pasta, or pizza; packaged bread, cookies, or cakes; and soft drinks, candy, chicken nuggets, or fast food. Ultra-processed foods tend to be delicious, cheap, convenient, and packed with ingredients.

One problem with the NOVA system is that it attempts to broadly define how healthy a food is based on ingredients added during processing, which can be confusing. It may also inadvertently promote notions of “good” and “bad” foods.

This can be harmful to people who eat a balanced diet or have an eating disorder, and can lead to excessive restriction of food intake.

Should you limit ultra-processed foods?

Many ultra-processed foods are convenient and cheap compared to some natural foods, making them difficult for most people to avoid. Also, it’s okay to have a sweet treat or soft drink from time to time.

But the more processed a food is, the more likely it is to contain extra calories, salt and sugar.

Research shows that eating high amounts of ultra-processed foods is linked to obesity, diabetes, high blood pressure and dementia. The aforementioned 2022 study linked ultra-processed foods to cognitive decline.

If you’re eating processed foods but are watching the number of calories you’re eating overall, some ultra-processed foods may not be a cause for concern.

Try to stick to the 80/20 rule, which is to focus on eating unprocessed or minimally processed foods 80% of the time.

Give yourself some grace and realize that it can be challenging to avoid overly processed foods entirely.

Which processed foods are the healthiest to eat?

The simplest way to think about it is the fewer ingredients the better. If you start reading an ingredient list and you can’t understand or even pronounce what’s in it, try not to eat it too often.

Choosing healthy foods can be confusing, especially when the label says something like “all natural” or “made with whole grains,” but it contains many other ingredients that make it ultra-processed.

To ensure you choose the option with the least amount of processing most of the time:

• Look for items with five or fewer ingredients (or items with the shortest ingredient list).
• Pay attention to the first ingredient listed – that’s what the product contains the most (for example, look for bread that lists “whole grain” first rather than “enriched flour”).
• Avoid (or minimize) added sugars, saturated fat, and products high in sodium (20% or more of daily sodium intake per serving is considered high sodium).
• Choose foods that are as close to their natural state as possible.

Planning meals and snacks ahead of time and doing a certain amount of meal prep can help reduce the frequency of needing these convenience foods.