Minimally processed foods boost dietary quality, while ultra-processed harm it, study finds

By Neha MathurReviewed by Benedette Cuffari, M.Sc.Apr 4 2023

In a recent article published in the Journal of the Academy of Nutrition and Dietetics, researchers performed a cohort study among female and male health professionals in the United States of America between 1986 and 2010.

Herein, the researchers assessed whether the consumption of unprocessed and minimally processed food (UMP) and ultra-processed food (UPF) was associated with three diet-quality metrics including the alternate healthy eating index (AHEI)-2010, Mediterranean diet index (aMED), and dietary approaches to stop hypertension (DASH)-diet score.

Study: Intakes of unprocessed and minimally processed and ultra-processed food are associated with diet-quality in female and male health professionals in the United States: a prospective analysis. Image Credit: Zu Kamilov / Shutterstock.com

Background

UMP and UPF are two of the four food-processing categories created by the NOVA classification system. The UMP category includes vegetables, nuts, fruits, whole grains, and animal-derived foods, which are preservative- and additive-free. These food products are also nutrient-dense and contain vitamins, minerals, and mono- and polyunsaturated fat (MUFA and PUFA, respectively).

The UPF category includes foods that are ready-to-eat and ready-to-heat, such as factory-made bread, sweet and savory snacks, and sugar-sweetened beverages. UPF intake was also identified as a risk factor associated with chronic diseases.

The consumption of UMP foods has been associated with a lower risk of chronic diseases. However, it remains unknown whether the consumption of UMP and UPF are associated with diet-quality factors and whether UMP and UPF intake and diet quality have changed over time.

About the study

In the present study, researchers invited participants from two U.S. cohorts including the Nurses’ Health Study (NHS) and Health Professionals Follow-up Study (HPFS).

The NHS, which was initiated in 1986, ran until 2010 and comprised 121,700 female registered nurses aged 30 to 55 years. Comparatively, the HPFS, which began in 1986 and ended in 2006, consisted of 51,529 male health professionals between 40 and 75 years of age.

The team assessed the diet quality of the study participants over time using a semi-quantitative food frequency questionnaire (SQFFQ) sent every four years to gather data on each participant's diet and lifestyle based on the hypothesis that higher average diet quality scores would correlate with lower UPF and higher UMP intake over time. All study participants also completed a mailed questionnaire on medical history and health-related behavior every two years.

Results

The response rate of the study participants was about 90% each cycle. According to UMP and UPF intake quintiles, diet-quality scores varied significantly among all study participants, with these associations varying slightly over time. With increasing quintiles of UMP intake, diet-quality scores also rose.

The study results were well-aligned with the hypothesis that all diet-quality metrics were inversely associated with UPF intake quintiles. Strikingly, changes in diet-quality metrics per quintile of UMP and UPF intakes correlated with aMED when expressed as energy percentage.

The approach employed in the current study established a correlation between UMP intake and diet quality metrics. Notably, the three all diet-quality metrics assessed in this study did not directly consider the level of food processing.

The correlation between UMP and UPF intakes and diet quality was due to their unique nutrient composition. UMP intake supplemented the body with multivitamins, minerals, and unsaturated fats, which lowered rates of non-infectious disease risk. The features of diet-quality metrics explained the observed correlation between the consumption of UMP foods with the three evaluated diet-quality metrics.

A diet comprised of high amounts of UMP foods, such as fruits, vegetables, nuts, legumes, and unprocessed cereals, received high aMED scores. Interestingly, the aMED also included modest wine consumption during meals; however, UMP and UPF categories excluded alcoholic beverages.

Conclusions

An association between UMP consumption with good diet quality and UPF consumption with poor dietary quality was observed. Furthermore, a direct correlation between UMP intake and AHEI-2010, aMED, and DASH-diet scores was observed, whereas an inverse correlation of UPP intake was identified with these three diet scores. The observed associations were not temporally consistent, which was partially due to the processing categories or SQFFQ changes.