A new study shows that eating mostly minimally processed foods, as defined by the NOVA classification system, does not automatically constitute a healthy diet, suggesting that the types of foods we eat may matter more than the level of processing used to make them.
Comparing two menus reflecting a typical Western diet—one emphasizing minimally processed foods and the other emphasizing ultra-processed foods, as categorized by the NOVA classification system—the researchers found that the less processed menu was more than twice as expensive and reached its expiration date three times faster without providing any additional nutritional value.
“This study shows that it is possible to eat a poor-quality diet even if you choose mostly minimally processed foods,” said Julie Hess, Ph.D., a nutrition researcher at the USDA-ARS Human Nutrition Research Center in Grand Forks, who led the study. “It also shows that more or less processed diets can be equally nutritious (or not nutritious), but that the more processed diet may have a longer shelf life and be less expensive.”
Mark Messina, PhD, director of nutritional sciences and research at the Soy Nutrition Institute Global, will present the findings at NUTRITION 2024, the flagship annual meeting of the American Society for Nutrition, taking place June 29-July 2 in Chicago.
The new study builds on a study the team published last year that showed it was possible to create a high-quality menu that met 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, with 20% of calories coming from ultra-processed foods, and a more processed menu, with 67% of calories coming from ultra-processed foods. The level of processing involved in each menu was determined using the NOVA classification system.
Both menus were calculated to have a healthy eating index of about 43-44 out of 100, a relatively low score that reflects low adherence to 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 expiration time for the less processed menu items was 35 days, compared to 120 days for the more processed menu items.
The study draws attention to the disconnect between food processing and its nutritional value. Hess noted that some nutrient-dense packaged foods can be classified as ultra-processed, such as unsweetened applesauce, ultrafiltered milk, liquid egg whites and some brands of raisins and canned tomatoes.
The results of this study indicate that developing a nutritious diet involves more than simply considering food processing as defined by NOVA. The concepts of “ultra-processed” and “less processed” foods need to be better characterized by the nutrition research community.
Julie Hess, Ph.D., nutrition researcher at the USDA-ARS Human Nutrition Research Center in Grand Forks
Messina will present this research from 12:45 p.m. to 1:45 p.m. CDT on Sunday, June 30, at the Food Choice, Markets, and Policy poster session at McCormick Place (abstract; (presentation details below).
Goals: The trend toward eating primarily foods with simple ingredients suggests that eating less processed foods is a necessary aspect of a healthy diet. However, research indicates that a menu containing primarily ultra-processed foods (UPFs) can meet the nutritional quality and dietary recommendations of the Dietary Guidelines for Americans. Whether a diet consisting primarily of foods with simple ingredients can provide a poor-quality diet remains to be determined. The objective of this study was to compare the dietary quality, shelf stability, and cost of two similar Western-style menus, one containing energy primarily from UPFs and the other containing energy primarily from less processed foods, as defined by the Nova Food Classification System.
Methods : First, a less processed version of a Western menu (least processed Western, LPW; most processed Western MPW) with a Healthy Eating Index (HEI) score of approximately 43 was developed to align with the previously developed MPW HEI score. The level of processing was determined by Nova categorizations assigned by external raters. The final menu was assessed for nutrient content and HEI score. Shelf stability of foods was determined using information from food storage guidance manuals. The condition of each food at the time of purchase (shelf stable, frozen, refrigerated) was used to estimate days to expiration. Food and menu costs were determined using retail prices from a Midwestern grocery chain in the fall of 2023.
Results: LPW and MPW had similar nutrient densities and HEI scores (44 and 43, respectively). LPW included 20% of energy (kcal) from UPF, while MPW included 67% of energy from UPF. 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 versus 120 days for MPW menu items. The “per person” cost was $34.87/day for LPW and $13.53/day for MPW.
Conclusions: Both the less-processed and more-processed menus provided poor-quality diets. However, LPW was more than twice as expensive as MPW and had a shorter overall shelf life. The 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 sources: USDA Agricultural Research Service Project Grant No. 3062-51000-057-00D
Source:
American Nutrition Society
Article Revisions
- 3 July 2024 – Expert reaction to unpublished conference presentation on whether limiting ultra-processed foods improves diet quality https://www.sciencemediacentre.org/expert-reaction-to-unpublished-conference-presentation-on-whether-limiting-ultra-processed-food-improves-diet-quality/ – Dr Hilda Mulrooney, Senior Lecturer in Nutrition and Health at London Metropolitan University, discussed a groundbreaking study at Nutrition 2024 that criticises the NOVA classification system, which categorises foods based solely on how processed they are. She pointed out that this approach neglects the nutritional value of foods. The study found that it is possible to eat a diet high in ultra-processed foods (UPF) and still meet national dietary guidelines.
- July 3, 2024 – This article has been temporarily removed pending review. While the research summary and press release appear to attempt to debunk the idea that minimally processed foods are inherently healthier, they overlook several key aspects. First, it is misleading to equate cost and shelf life with diet quality; health benefits often come at a price. Second, the low Healthy Eating Index scores for both menus may suggest a poorly designed study, as a truly balanced diet would score higher regardless of the level of processing. Finally, focusing solely on NOVA classifications without considering food quality and nutrient density gives an incomplete picture of dietary health. Once the full peer-reviewed article is available, we will update this article accordingly.
- July 2, 2024 – The title has been changed from “Eating mostly minimally processed foods is not a healthy diet, study finds” to better communicate that this content is a press release of results presented at NUTRITION 2024 and is not a peer-reviewed study.