Diets high in less processed foods are not necessarily nutritionally superior to those high in more processed foods: a study comparing two Western diets found that nutritional scores were similar, but less processed foods were more expensive and had a shorter shelf life.
New research casts doubt on the level of processing as an indicator of diet quality.
A recent study challenges the notion that less processed foods automatically translate to a healthier diet, finding that less and more processed diets may have similar nutritional value or may lack nutritional value. The study highlighted that less processed diets may have a higher cost and shorter shelf life despite lacking nutritional benefits, highlighting the complexity of defining diet quality in terms of processing level alone.
Food choices and levels of processing
New research demonstrates that eating primarily less processed foods, as defined by the NOVA classification system, does not necessarily lead to a healthier diet, suggesting that the types of foods we eat may be more important than the degree of processing used to make them.
The researchers compared two menus reflecting the typical Western diet – one that emphasized less processed foods, as classified by the NOVA classification system, and one that emphasized more highly processed foods – and found that the less processed menus were more than twice as expensive, offered less nutritional value, and expired more than three times faster.
Examples of highly processed (left) and less processed (right) breakfasts. None of the ingredients in the less processed meal would be considered ultra-processed (both the bread and jam are homemade), whereas almost all of the ingredients in the more processed meal would be considered ultra-processed. Credit: Courtesy of USDA-ARS
Research findings on processed and minimally processed foods
“This study shows that it’s possible to eat a low-quality diet even if you choose mostly less processed foods,” said Julie Hess, PhD, a nutritionist researcher at the USDA.“Our results suggest that highly and less processed diets may have similar nutritional value, but that more processed diets may have a longer shelf life and may also be less costly,” said lead study scientist from the ARS Grand Forks Human Nutrition Research Center.
Dr. Mark Messina, director of nutritional science research at Soy Nutrition Institute Global, recently presented the findings at NUTRITION 2024, the American Academy of Nutrition’s flagship annual meeting.
Assessment of the nutritional value of different diets
This new study study Last year, the team published a paper demonstrating that it was possible to create a high-quality menu that adhered to dietary guidelines and still get the majority of its calories from foods classified as ultra-processed. In the new study, the researchers asked the opposite question: Is it possible to create a low-quality menu that gets the majority of its calories from “simple” foods?
To find out, the researchers created a low-processed menu, with 20% of calories coming from ultra-processed foods, and a high-processed menu, with 67% of calories coming from ultra-processed foods. The level of processing for each menu was determined according to the NOVA classification system.
The Healthy Eating Index for the two menus was calculated to be 43-44 out of 100, a relatively low score indicating low adherence to the Dietary Guidelines for Americans. The researchers estimated that the less processed menu would cost $34.87 per person per day compared to $13.53 per person per day for the more processed menu. They also calculated that the median shelf life of the less processed menu was 35 days compared to 120 days for the more processed menu.
The study looked at the disconnect between food processing and nutritional value, and Hess noted that some highly nutritious packaged foods could be classified as ultra-processed, including unsweetened applesauce, ultrafiltered milk, liquid egg whites, and some brands of raisins and canned tomatoes.
“The findings of this study suggest that constructing a nutritious diet requires more than considering food processing as defined by NOVA,” Hess said. “The concepts of ‘ultra-processed’ and ‘lowly processed’ foods need to be more clearly defined by the nutrition research community.”
Unprocessed but sad: The standard American diet of minimally processed foods is still the standard American diet
Presenter:
Julie M. Hess, PhD, USDA-ARS Grand Forks Human Nutrition Research Center
Mark Messina, PhD, MSc, Director of Nutrition Science Research, Soy Nutrition Institute, Global
Co-authors:
Madeline E. Como, MS, USDA-ARS Grand Forks Human Nutrition Research Center
Angela J. Sheets, USDA-ARS Grand Forks Human Nutrition Research Center, University of North Dakota
Anne Bodensteiner, Ph.D., RDN, LRD, University of North Dakota
Allen S. Levine, University of Minnesota, USA
Daniel Palmer, USDA-ARS Grand Forks Human Nutrition Research Center
The trend towards “clean eating” with a focus on simple foods suggests that reducing the intake of processed foods is an essential component of a healthy dietary pattern. However, studies have shown that menus containing primarily ultra-processed foods (UPFs) can meet the nutrient and dietary quality recommendations of the Dietary Guidelines for Americans. Whether a diet containing primarily simple foods constitutes a lower quality diet has yet to be investigated. The aim of this study was to compare the dietary 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, we developed less processed Western menus (Less Processed Western, LPW; More Processed Western, MPW) with a Healthy Eating Index (HEI) score of approximately 43 to match the HEI score of the previously developed MPW. The level of processing was determined by the Nova classification assigned by an external assessor. The final menus were evaluated for nutritional content and HEI score. The shelf life of the foods was determined using information from the Food Storage Guidance Manual. The status of each food item at the time of purchase (shelf-stable, frozen, refrigerated) was used to estimate the number of days until expiration. The costs of the foods and menus were determined using fall 2023 retail prices from a Midwestern grocery chain.
LPW and MPW had similar nutrient density and HEI scores (44 and 43, respectively). LPW contained 20% energy (kcal) from UPF, whereas MPW contained 67% energy from UPF. The relative proportions of shelf-stable, frozen, and refrigerated foods were similar between the two. Using Kaplan-Meier survival analysis, the median shelf life of LPW menu items was 35 days compared to 120 days for MPW menu items. The “per person” cost was $34.87/day for LPW and $13.53/day for MPW.
Both the less and more processed menus offered lower quality meals, but the LPW was more than twice as expensive as the MPW and had a shorter overall shelf life. 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
