Food consumers often do not understand the nutritional information given on packaging labels, according to a comprehensive US study published in the American Journal of Preventive Medicine.

Vanderbilt University Medical Centre researchers have found that the reading and mathematical skills of a significant number of consumers may actually be insufficient to extract needed dietary information from labels. For instance, only 60% of research subjects could calculate the number of carbohydrates consumed if they ate half a bagel, when the serving size was a whole bagel. Only 22% of subjects could determine the amount of net carbohydrates in 2 slices of low-carb bread, and only 23% could determine net carbohydrates in a serving of low-carb spaghetti.

Common reasons for incorrect responses included misapplication of the serving size, confusion by extraneous material on the food label, and incorrect calculations. Researchers said 68% of test participants had at least some university education, and 77% had at least 15-16-year old standard literacy skills.