While experts agree that school meal programs should offer children more whole grains, many school officials may be confused about what a whole grain is, a new study suggests.

In interviews with 36 foodservice directors from Minnesota school districts, researchers found that many had difficulty defining what constitutes a whole-grain product.

Administrators also said they wanted clearer, more uniform standards in how to purchase whole-grain foods for their schools.

Dr. Len Marquart and colleagues at the University of Minnesota in Minneapolis report the findings in the Journal of Child Nutrition and Management.

Whole grains are those that contain all three main grain components -- the innermost endosperm, plus the more nutrient-rich bran and germ layers. Barley, oats (including oatmeal), brown rice, quinoa, whole wheat and whole cornmeal are some examples. The grain can be processed -- cracked, rolled or cooked, for instance -- but it must contain the three grain components to be considered whole grain.

Confusion often sets in when a processed product, such as bread, pasta or crackers, contain a mix of whole grains and refined grains -- grains that have been largely stripped of the bran and germ layers.

"Currently, there is no standard definition for whole grain foods that allows for universal use in school food service," Marquart and his colleagues write.

By one proposed definition, the researchers note, the flour in a whole-grain product must be at least 51 percent whole-grain, while the rest can be all-purpose white flour. Another definition, devised by the U.S. Department of Agriculture for use in schools, is that a product must provide 14.75 grams of whole grain per serving.

Marquart and his colleagues also found that product labeling was an "urgent point of contention" among the foodservice directors they interviewed. Many thought label wording such as "multigrain" and "50 percent whole grain" was misleading when compared with what was on the product's actual ingredient list.

"The participants overwhelmingly supported the idea of some type of logo or indicator to certify a product's whole grain status," the researchers report.

"The goal is to remove confusion surrounding the definition of a whole-grain food and to provide simple standards to follow when ordering whole grain products for school meals," Marquart said in university-issued statement.

"This," he added, "will require working together -- enhanced communication among vendors, distributors and manufacturers along with key players in government, industry and school food service."