Diets high in minimally processed foods do not necessarily offer better nutritional benefits than diets with more ultra-processed foods. One study comparing two Western diets found similar nutritional scores but noted that minimally processed foods were more expensive and had shorter shelf lives.
A new study questions whether level of processing is an indicator of diet quality.
Recent research challenges the idea that minimally processed foods automatically lead to a healthier diet, finding that both minimally and ultra-processed diets can be equally nutritious or lacking in nutrients. The study highlights that minimally processed diets can be more costly and have a shorter shelf life without additional nutritional benefits, highlighting the complexity of defining diet quality based solely on levels of processing.
Dietary Choices and Processing Levels
A new study shows that eating primarily minimally processed foods, as defined by the NOVA classification system, does not automatically constitute a healthy diet. It suggests that the types of foods we eat may be more important than the level of processing used to make them.
Comparing two menus reflecting a typical Western diet (one emphasizing minimally processed foods, the other emphasizing ultra-processed foods according to the NOVA classification system), the researchers found that the less processed menu was twice as expensive and expired three times faster without providing any additional nutritional value.
Examples of more processed (left) and less processed (right) breakfasts. None of the ingredients used to make the less processed meal are considered ultra-processed (both the bread and jam are homemade), while nearly all of the ingredients in the more processed meal are considered ultra-processed. Source: Courtesy of USDA-ARS
Research Findings on Processed and Minimally Processed Diets
“This study shows that it is possible to eat a poor-quality diet even when choosing mostly minimally processed foods,” said Dr. Julie Hess, 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 so nutritious), but the more processed diet may have a longer shelf life and cost less.”
Dr. Mark Messina, director of nutrition science and research at Soy Nutrition Institute Global, recently presented his findings at NUTRITION 2024, the American Society for Nutrition’s flagship annual meeting.
Assessment of Nutritional Quality in Different Diets
The new research builds on a study the team published last year that showed it was possible to create a high-quality menu that complies with 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 that got 20% of its calories from ultra-processed foods and a more processed menu that got 67% of its calories from ultra-processed foods. The level of processing in each menu was determined according to the NOVA classification system.
Both menus were calculated to have a Healthy Eating Index score of approximately 43-44 out of 100, a relatively low score reflecting poor adherence to the Dietary Guidelines for Americans. The researchers estimated that the less processed menu would cost $34.87 per person per day, while the more processed menu would cost $13.53 per person per day. They also calculated that the median expiration time for the less processed menu items was 35 days, while the more processed menu items were 120 days.
The study highlights the disconnect between food processing and nutritional value. Some nutrient-dense packaged foods, such as unsweetened applesauce, ultra-filtered milk, liquid egg whites and some brands of raisins and canned tomatoes, could be classified as ultra-processed, Hess said.
“The results of this study suggest that creating 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 defined by the nutrition research community.”
Unprocessed but SAD: A standard American diet 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 Nutrition 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 of primarily consuming simple foods suggests that consuming less processed foods is a necessary aspect of healthy eating patterns. However, research suggests that a menu consisting mostly of ultra-processed foods (UPFs) may meet the nutrient and diet quality recommendations in the Dietary Guidelines for Americans. Whether a diet consisting mostly of simple foods may provide a low-quality diet has not yet been studied. The purpose of this study was to compare the diet quality, shelf life, and cost of two similar Western-style menus, one containing primarily energy from UPFs and the other containing primarily energy from less processed foods as defined by the Nova food classification system.
First, a less processed Western menu version (less processed Western, LPW; more processed Western, MPW) was developed with a Healthy Eating Index (HEI) score of approximately 43, which would be consistent with the HEI score of the previously developed MPW. Level of processing was determined by Nova categorizations assigned by external raters. The final menu was evaluated for nutrient content and HEI score. Shelf life of foods was determined using information from food storage guidelines. The condition of each food item when purchased (extended, frozen, refrigerated) was used to estimate the number of days until expiration. Food and menu costs were determined using retail prices at a Midwestern grocery chain in Fall 2023.
LPW and MPW had similar nutrient densities and HEI scores (44 and 43, respectively). LPW contained 20% energy (kcal) from UPFs, while MPW contained 67% energy from UPFs. The 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 expiration for LPW menu items was 35 days, compared with 120 days for MPW menu items. The “per person” cost was $34.87 per day for LPW and $13.53 per day for MPW.
Both less processed and more processed menus provided lower quality diets. However, LPW was twice as expensive as MPW and had a shorter overall shelf life. Level of processing is not a proxy for diet quality, and less processed foods may be more expensive and have a shorter shelf life.
Funding: USDA Agricultural Research Service project grant #3062-51000-057-00D