The results presented show that eating mainly minimally processed foods does not make for a healthy diet

A new study finds that eating mostly minimally processed foods, as defined by the NOVA classification system, does not automatically lead to a healthy diet. This suggests that the type of food we eat may be more important than the amount of processing that goes into producing it.

When comparing two menus reflecting a typical Western diet — one with an emphasis on minimally processed foods and the other with an emphasis on extremely processed foods, categorized according to the NOVA classification system — the researchers found that the least processed menu was more than twice as expensive and expired three times faster, without providing any additional nutritional value.

“This study suggests that it is possible to eat a low-quality diet even if you choose minimally processed foods,” said Julie Hess, PhD, a research nutritionist at the USDA-ARS Grand Forks Human Nutrition Research Center, who led the study. “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 expensive.”

Mark Messina, PhD, director of nutrition science and research at Soy Nutrition Institute Global, will present the findings at NUTRITION 2024, the flagship annual meeting of the American Society for Nutrition, held June 29–July 2 in Chicago.

The new research builds on a study the team published last year, which showed that it was possible to create a high-quality menu that meets dietary guidelines while getting most of its calories from foods classified as ultra-processed. For the new study, the researchers asked the opposite question: Is it possible to create a low-quality menu that gets most of its calories from “simple” foods?

To find out, they created a less processed menu, which got 20 percent of its calories from ultra-processed foods, and a more processed menu, which got 67 percent of its calories from ultra-processed foods. The level of processing used in each menu was determined using the NOVA classification system.

The two menus were found 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. The researchers estimated that the less processed menu would cost $34.87 per day per person, compared to $13.53 per day for the more processed menu. They also calculated that the median time to shelf life for the less processed menu items was 35 days, versus 120 days for the more processed menu items.

The study highlights the discrepancies between food processing and nutritional value. Hess noted that some nutrient-dense packaged foods can be classified as ultra-processed, such as unsweetened applesauce, ultra-filtered milk, liquid egg whites, and some brands of canned raisins and tomatoes.

The results of this study indicate that designing a nutritious diet involves more than just considering food processing as defined by NOVA. The concepts of “ultra-processed” foods and “less-processed” foods need to be better characterized by the nutrition research community.”

Julie Hess, PhD, research nutritionist at the USDA-ARS Grand Forks Human Nutrition Research Center

Messina will present this research on Sunday, June 30 from 12:45 to 1:45 p.m. CDT during the Food Choice, Markets and Policy poster session at McCormick Place (abstract; (see presentation details below).

Goals: The clean eating trend toward consuming primarily foods with simple ingredients suggests that consuming less processed foods is a necessary aspect of healthy dietary patterns. However, research suggests that a diet consisting primarily of ultra-processed foods (UPFs) can meet the nutrient and diet quality recommendations of the Dietary Guidelines for Americans. Whether a diet consisting primarily of foods with simple ingredients can provide a low-quality diet has not been studied. The purpose of this study was to compare the diet quality, shelf life, and cost of two comparable Western-style menus, one of which provides energy primarily from UPFs and the other of which provides energy primarily from less processed foods, as defined by the Nova food classification system.

Methods: First, a less processed version of a Western menu (less processed Western, LPW; more processed Western MPW) with a Healthy Eating Index (HEI) score of approximately 43 was developed to align with the HEI score of the previously developed MPW. The level of processing was determined by Nova categorizations assigned by external raters. The final menu was scored for nutritional content and HEI score. Shelf life of foods was determined using information from food storage manuals. The condition of each food item at purchase (shelf-stable, frozen, refrigerated) was used to estimate the number of days until the expiration date. Food and menu costs were determined using retail prices at a Midwestern grocery store chain in the fall of 2023.

Results: The LPW and MPW had similar nutrient densities and HEI scores (44 and 43, respectively). The LPW contained 20% of energy (kcal) from UPFs, while the MPW contained 67% of energy from UPFs. Relative percentages of shelf-stable, frozen, and refrigerated foods were similar between the two. Using the Kaplan-Meier survival analysis method, the median time to shelf life for the LPW menu items was 35 days versus 120 days for the MPW menu items. The “per person” costs were $34.87/day for the LPW and $13.53/day for the MPW.

Conclusions: The less processed and more processed menus both provided low-quality diets. However, the LPW was more than twice as expensive as the MPW and had a shorter overall shelf life. The 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.

Sources of funding: USDA Agricultural Research Service project grant #3062-51000-057-00D