Not all foods that are labeled 'whole grain' are healthy, says a new study by researchers from Harvard School of Public Health.

The study found that the so called whole grain products actually had more calories and sugars than the foods that weren't labeled as whole grain food. Researchers say that standard labeling that's based on sound evidence can help consumers make better food choices.

"Given the significant prevalence of refined grains, starches, and sugars in modern diets, identifying a unified criterion to identify higher quality carbohydrates is a key priority in public health," said Rebecca Mozaffarian, project manager in the Department of Social and Behavioral Sciences at HSPH and lead author of the study .

There are numerous benefits of switching from refined food to whole-grains and these include lower risk of cardiovascular diseases, weight gain and diabetes type-2, according to a news release. And, although the U.S. Department of Agriculture's (USDA) 2010 Dietary Guidelines recommend at least three servings of whole-grains per day, there is no standard definition of whole grain.

For the study, researchers assessed different guidelines for whole grain products that are defined by industry and government like:

- The Whole Grain Stamp, developed by the Whole Grain Council.

- Labels that list whole grains as one of the main ingredients, use of whole grains anywhere on the label and any whole grain that's been listed on the label without the mention of added sugars (recommended by the USDA).

- The "10:1 ratio", a standard recommended by the American Heart Association's 2020 Goals and is the ratio of total carbohydrates to fiber of less than 10:1.

Researchers identified more than 500 grain products from U.S. grocers. The products included bread, bagels, English muffins, cereals, crackers, cereal bars, granola bars, and chips. Researchers then collected ingredient list, nutrition content and whether the product had Whole Grain Stamp on it.

Study analysis showed that products that had the Whole Grain Stamp (one of the most widely used symbols) were also the ones that had high sugar and more calories than food products that didn't have the stamp.

Researchers found that products labeled with the American Heart Association's standard that is a ratio of total carbohydrate to fiber of ≤10:1 was the best indicator of the product's healthfulness. These products were higher in fiber, but lower in fat, sugar and salt. Also, these products were low in calories.

"Our results will help inform national discussions about product labeling, school lunch programs, and guidance for consumers and organizations in their attempts to select whole grain products," said Steven Gortmaker, professor of the practice of health sociology and senior author of the study.