Diets rich in minimally processed foods don’t necessarily provide better nutritional benefits than those with more ultra-processed items. A study comparing two Western diets found similar nutritional scores, but noted that minimally processed foods were more expensive and had a shorter shelf life.
A new study questions the degree of processing as a measure of diet quality.
Recent research challenges the idea that minimally processed foods automatically lead to a healthier diet, showing that both minimally and ultra-processed diets can be equally or less nutritious. The study highlighted that minimally processed diets can be more expensive and have a shorter shelf life without additional nutritional benefits, highlighting the complexity of defining diet quality based on processing levels alone.
Dietary choices and processing levels
New research shows that eating mostly minimally processed foods, as defined by the NOVA classification system, doesn’t automatically make for a healthy diet. It suggests that the types of foods we eat may be more important than the amount of processing that went into making them.
Comparing two menus that reflect a typical Western diet — one with an emphasis on minimally processed foods and the other with an emphasis on ultra-processed foods, as categorized by the NOVA classification system — the researchers found that the less processed menu cost more than twice as much and reached its expiration date more than three times faster, without any additional nutritional value.
Examples of a more processed (left) and less processed (right) breakfast. None of the ingredients used to make the less processed meal are considered ultra-processed (both the bread and the jam are homemade), while almost all components of the more processed meal are considered ultra-processed. Credit: Courtesy of USDA-ARS
Research Findings on Processed vs. Minimally Processed Diets
“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 not 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, recently presented the findings at NUTRITION 2024, the flagship annual meeting of the American Society for Nutrition.
Evaluating the nutritional quality of different diets
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,” Hess said. “The concepts of ‘ultra-processed’ foods and ‘less-processed’ foods need to be better characterized by the nutrition research community.”
Unprocessed, but SAD: A standard American diet made with less processed foods is still a standard American diet
Presenting authors:
Julie M. Hess, PhD, USDA-ARS Grand Forks Human Nutrition Research Center
Mark Messina, PhD, MS, director of nutritional science and research, Soy Nutrition Institute Global
Co-authors:
Madeline E. Comeau, MS, USDA-ARS Grand Forks Human Nutrition Research Center
Angela J. Scheett, USDA-ARS Grand Forks Human Nutrition Research Center; University of North Dakota
AnneBodensteiner, Ph.D., RDN, LRD, University of North Dakota
Allen S. Levine, University of Minnesota, United States
Daniel Palmer, USDA-ARS Grand Forks Human Nutrition Research Center
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.
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.
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.
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.
Funding: USDA Agricultural Research Service project grant #3062-51000-057-00D