BOSTON — Two studies published this fall show a need for a standardized definition of whole grain food. One study, published Nov. 30 in The American Journal of Clinical Nutrition, found an increase in whole grain food intake over 15 years, but the level of the increase depended on the definition of a whole grain food. The other study, published in the Nov. 12 issue of the Journal of Nutrition Education and Behavior, found the labeling of whole grain products confused Australian consumers.

In the AJCN study, researchers from the Boston-based Friedman School of Nutrition Science and Policy at Tufts University found whole grain intake in the United States increased 39.5% to 61.5%, depending on which whole grain food definition was used. No matter the definition, the US mean consumption of whole grain foods per person remained below the recommended daily consumption of at least 3 oz. The research involved 39,755 US adults of the ages 20 and over in the National Health and Nutrition Examination Survey between 2003 and 2018. The National Institutes of Health supported the study.

The study followed whole grain intake based on definitions from the American Heart Association, the Dietary Guidelines for Americans and the Cereals & Grains Association (formerly known as AACC International).

“We found that each definition captured very different types of grain- or flour-containing foods as whole grain foods, resulting in differences in the average consumption of whole-grain foods and the associated trends,” said Mengxi Du, lead author of the study and a PhD candidate in the Nutrition Epidemiology and Data Science program at the Friedman School.

The greatest increase in whole grain intake, 61.5%, came under the whole grain food definition from the American Heart Association, Dallas, which states whole grain foods are whole grain-rich foods having more than 1.1 grams of fiber or more per 10 grams of carbohydrates. Under that definition, the mean daily whole grain intake increased to 1.05 oz from 0.65 oz.

The 2015-2020 Dietary Guidelines for Americans defines whole grain foods as foods containing 50% or more (by weight) of the grain- or flour-containing component as whole grain ingredients. Under that definition, the mean intake increased to 0.81 oz from 0.50 oz. The definition from the Cereal & Grains Association states a whole grain food must contain at least 50% whole grain ingredients based on dry weight. The mean intake increased to 0.73 oz from 0.51 oz under that definition.

The researchers concluded a standardized definition of whole grain foods would guide consumers, industry and policymakers in promoting whole grain intake.

“We can’t say which is the best definition yet as we need to assess the nutrient profiles of each and how these different definitions are associated with health outcomes,” said Fang Fang Zhang, PhD, senior author of the study and interim chair of the Division of Nutrition Epidemiology and Data Science at the Friedman School. “Our findings, however, underscore the imperative need for a consensus on whole-grain food definition. A consistent definition across agencies is essential to further promoting whole-grain food consumption in the US population.”

Non-Hispanic white consumers had a higher intake of whole grain foods than other racial/ethnic groups under all definitions except the one for the American Heart Association, where Hispanic consumers had the highest intake. The researchers said the reason may be the heart association’s definition identifies food such as corn-based burritos, tacos and nachos as whole grain foods.

The study noted the Whole Grains Council’s qualifications for its Whole Grain Stamp: the food must contain 8 grams or more of whole grain ingredients per labeled serving. The study did not measure increases under this definition.

The Australian study involved 43 consumers of the ages 18 or over who purchase or consume grain foods and 17 participants currently or recently employed by grain food companies in roles such as dietitians, food scientists, marketers and regulatory personnel. Findings suggested definitions and regulations, consumer education, and strategies addressing factors that influence consumer choices are needed to improve whole grain intake. Researchers came from the University of Wollongong in Wollongong, Australia, and the Illawarra Health and Medical Research Institute in Wollongong.

The consumers were provided front-of-pack labeling for three bread products and five ready-to-eat cereal products that contained whole grain and were sold on Australian supermarket shelves. The food industry workers were interviewed.

Consumers were more likely to choose a product containing a whole grain label, even if it contained a lower whole grain content and had other nutritional disadvantages than other products, which indicated front-of-pack labeling often misled consumers. Consumers expressed skepticism in labeling, whole grain content claims, symbols such as the Health Star rating and products marketed as healthy. Consumers considered a statement on the percentage of whole grain in a product as clear and easy to understand.