In US homes, more than three-fourths of calories come from moderately and highly processed foods and beverages

June 1, 2015

Soda, cheese puffs and candy likely spring to mind when you think of processed foods. You might be surprised to know that milk, dried fruit, and frozen vegetables are processed foods, too.

The United States government defines food processing as any procedure that alters food from its natural state. This includes pasteurizing, drying, freezing and canning as well as adding ingredients – most commonly, sugar, salt and fat.

Dr. Jennifer Poti

To better examine the relationship between food’s degree of processing, convenience of preparation and nutritional quality, Jennifer Poti, PhD, research assistant professor of nutrition at the UNC-Chapel Hill Gillings School of Global Public Health, developed classification systems to subdivide food products into categories based on the complexity and purpose of processing. These four categories range from “unprocessed/minimally processed” to “highly processed.”

Foods and beverages were also classified based on convenience to distinguish items that are ready-to-eat, ready-to-heat or require cooking or other preparation.

The research, co-authored by Michelle Mendez, PhD, assistant professor, Shu Wen Ng, PhD, research assistant professor, and Barry Popkin, PhD, W. R. Kenan, Jr. Distinguished Professor, all in the Department of Nutrition at the Gillings School, was published in the June 1 issue of the American Journal of Clinical Nutrition.

The research team used the 2000-2012 Homescan Panel to analyze purchases of prepackaged food and beverages by more than 157,000 U.S. households. Using the categories developed, they classified the products by degree of industrial processing and convenience of food preparation.

After classifying more than 1.2 million products through the use of barcode-specific descriptions and ingredient lists, the researchers compared median saturated fat, sugar and sodium content across levels of processing and convenience.

They found a stable trend between 2000 and 2012, in which more than three-fourths of calories in prepackaged purchases came from moderately (15.9 percent) and highly (61.0 percent) processed foods and beverages.

Upon examining each household’s total food purchases in 2012, the team learned that the percent of households that purchased highly processed foods and beverages containing high levels of saturated fat, sugar and sodium (60.4 percent) was far higher than the percent of households that purchased less-processed food exceeding recommended limits for those ingredients (5.6 percent).

“We found no significant increases or decreases in highly processed food purchases across time, suggesting that these purchasing patterns have been remarkably resistant to any type of change in the past 15 years,” said Poti. “This finding could be cause for concern, because we also found that highly processed foods and beverages tend to contain high amounts of ingredients that dietary guidelines recommend we limit.”

Additionally, higher-convenience ready-to-eat (68.1 percent) and ready-to-heat (15.2 percent) products supplied the majority of caloric energy in purchases. Foods requiring cooking or preparation provided less than 20 percent of calories.

It is important to note the wide range of products found in each of the four different categories. Clearly, frozen vegetables, included in the minimally processed category, do not have the problematic added ingredients of highly processed foods such as mayonnaise and candy. Still, no single category contains foods that are uniformly “healthy” or “unhealthy.”

The main limitation of the data used in this analysis is that products without barcodes or unlinked to nutrition information – including unprocessed/minimally processed items (unpackaged fresh fruit, vegetables and raw meat) as well as highly processed items (deli meat and bakery items) – were not captured. Thus, the study findings pertain only to purchases of prepackaged goods, not total food and beverage purchases.