In a healthy diet, foods made with fewer ingredients and additives are more nutritious, right?

Not always, according to a new study that compared health attributes of more and less processed foods. In fact, researchers found the less processed foods cost more and had shorter shelf lives, without necessarily delivering more nutritional benefits than highly processed foods.

“This study indicates that it is possible to eat a low-quality diet even when choosing mostly minimally processed foods,” presenting author Julie Hess, PhD, said in a news release. Hess is a research nutritionist at the USDA-ARS Grand Forks Human Nutrition Research Center.

“It also shows that more-processed and less-processed diets can be equally nutritious (or non-nutritious), but the more-processed diet may have a longer shelf life and be less costly,” Hess said.

Researchers compared a less-processed menu with just 20% of calories derived from ultra-processed foods, with a menu that had 67% of calories from ultra-processed foods. They used the NOVA food classification system to characterize foods as more or less processed.

“The two menus were calculated to have a Healthy Eating Index score of about 43-44 out of 100, a relatively low score that reflects poor adherence to the Dietary Guidelines for Americans,” published by the U.S. Departments of Agriculture and Health and Human Services, the news release said.

While the nutritional values were similar, the prices were not. The more-processed foods cost $13.53 per person per day, but the less-processed foods were more than double the price at $34.87 per person per day, based on retail prices at a Midwestern grocery store chain in fall 2023. The more-processed foods also were estimated to last longer, with 120 days as a median time to expiration, compared with 35 days for the less-processed foods.

“Level of processing is not a proxy indicator of diet quality, and less processed foods can be more expensive and have a shorter shelf life,” the study abstract said.

In the news release, Hess said some packaged ultra-processed foods also can be dense with nutrients. Examples include unsweetened applesauce, ultrafiltered milk, liquid egg whites and some brands of raisins and canned tomatoes.

“The results of this study indicate that building a nutritious diet involves more than a consideration of food processing as defined by NOVA,” Hess in the news release. “The concepts of ‘ultra-processed’ foods and ‘less-processed’ foods need to be better characterized by the nutrition research community.”

The findings were to be presented at Nutrition 2024, the annual meeting of the American Society for Nutrition, scheduled June 29 to July 2 in Chicago.

Other ultra-processed foods, such as yogurts sweetened with sugar or whole grain breads, “are still nutrient-dense, accessible, and affordable sources of nutrients for Americans,” the researchers said in the 2023 study, “Dietary Guidelines Meet NOVA: Developing a Menu for A Healthy Dietary Pattern Using Ultra-Processed Foods.” In that study, the researchers created a menu with 91% of calories from ultra-processed foods, but with a Healthy Eating Index score of 86 out of 100 points.

The Dietary Guidelines for Americans are published every five years, with the current recommendations for the period 2020 to 2025. The NOVA food classification system was first published in 2009, but NOVA scoring of foods “can be inconsistent” among researchers, experts and consumers, including for ultra-processed foods. Defining those in the next set of Dietary Guidelines for Americans will be a challenge, the researchers said in the earlier study.