College of Health Solutions faculty and students analyze almost 2,000 foods, producing unexpected results

By: Aidan Hansen and Eden Miller

College of Health Solutions Associate Professor Karen Sweazea and ASU Alumnus and now State University of New York at Oneonta Assistant Professor Anthony Basile, along with ASU students and colleagues at the University of Sydney, analyzed data from nearly 2,000 foods to understand the relationship between the levels of processed foods using glycemic index and glycemic load.

According to the Academy of Nutrition and Dietetics, the glycemic index measures how much one’s blood sugar increases after eating.

However, GI only tells part of the story. According to Harvard Health, it is important to use glycemic load when measuring blood sugar levels. GL looks at how quickly sugar enters the bloodstream and how high your blood sugar level will rise.

Sweazea and Basile’s study examined GI and GL of the foods tested. Why did the team look at so many foods? One reason is a study on a similar subject published in 2016. The study only looked at 98 ready-to-eat foods, and Basile felt the sample size was too small.

“When I started learning about ultra-processed foods, there was one study that was constantly referenced when I would research the topic,” Basile said. “In that study, it talked about how ultra-processed foods have a high glycemic index.”

“That's what led to this project. The idea was, ‘let's try to get our hands on a bigger database and redo the same study,’” Basile said.

With data from nearly 2,000 foods gathered by a team at the University of Sydney, Sweazea and her team took nearly three years to complete their analysis, simultaneously looking at a database with a completed GI and GL for the majority of the foods included in the study.

The team used the NOVA Classifications system to define unprocessed or minimally processed foods, processed culinary ingredients, processed foods and ultra-processed foods. Their findings show the GI and GL are not associated with the NOVA Classifications.

The original hypothesis predicted the GI and GL would be lowest in minimally processed foods and highest in ultra-processed foods. The team found, across the sample size, it didn’t matter if a food was labeled ultra-processed or minimally processed. Both food types had a similar effect on blood sugar after eating.

“What we found was the complete opposite of that first study and opposite of what we had thought we hypothesized,” Basile said.

“Just because a food is processed doesn't necessarily mean it's going to raise your blood sugar,” Sweazea said. “Our study doesn't say that health problems aren't related to ultra-processed foods. It just says it's not necessarily the sugar aspect.”

Many factors go into determining whether a food is labeled as ultra-processed, including where it’s made. Food made in a factory is often classified as ultra-processed, even though the ingredients may be the same as those in the processed category. Any type of cooking is also considered processing a food, according to the NOVA classification system.

Additives to change the color or flavor of a food, as well as added preservatives and antioxidants can also lead to ultra-processed categorization. For example, red dyes may actually pose a health concern, but they may be put in the same category as foods that are thickened with a plant-based thickener with antioxidants.

“We have essentially ruled out one potential mechanism by which ultra-processed foods may have exerted an adverse effect (i.e. higher GI),” University of Sydney Professor Emerita Jennie Brand-Miller said.

“There are components of the diet other than GI or GL that may contribute to health problems,” Sweazea said. “Diet may just be an indicator of an overall difference in lifestyle too. If people are eating more ultra-processed foods, they may have other risk factors such as sedentary lifestyles, etc., that could contribute to disease risk.”

Another study published in December 2024 by Basile and Sweazea looked at the total antioxidant content found in a different set of 1,946 minimally processed, processed and ultra-processed food items. They found that minimally processed foods have a higher total antioxidant content than both processed and ultra-processed foods.

The results of these studies allow for a better understanding of ultra-processed foods which could inform dietary recommendations and future research.