Using standardized and validated tests for literacy (REALM -Rapid Estimate of Adult Literacy in Medicine) and numeracy (WRAT3 - Wide Range Achievement Test), researchers from Vanderbilt University Medical Center surveyed 200 primary care patients from a wide socioeconomic range. A Nutrition Label Survey (NLS), designed with input from registered dietitians, primary care providers, and experts in health literacy/numeracy to evaluate patient understanding of current nutrition labels, was used to measure comprehension of current food nutrition labels. One part of the NLS asked subjects to interpret food labels, such as determining carbohydrate or caloric content of an amount of food consumed. The other part asked patients to choose which of two foods had more or less of a certain nutrient, giving patients a 50/50 chance to guess the correct food item. Also, half of the survey questions involved products that were clearly labeled on their package as "reduced carb," "low carb," or designed for "a low-carb diet."
Sixty-eight percent of patients had at least some college education, and 77% had at least 9th-grade level literacy skills. However, 63% of patients had less than 9th-grade numeracy skills. Over 40% had a chronic illness for which specific dietary intervention is important (e.g., hypertension, diabetes), and 23% reported being on a specific diet plan. Most patients reported using food labels and found labels easy to understand.
Overall, patients correctly answered 69% (SD 21%) of the NLS questions. For example, only 32% of patients could correctly calculate the amount of carbohydrates consumed in a 20-ounce bottle of soda that had 2.5 servings in the bottle. Only 60% of patients could calculate the number of carbohydrates consumed if they ate half a bagel, when the serving size was a whole bagel. Only 22% of patients could determine the amount of net carbohydrates in 2 slices of low-carb bread, and only 23% could determine the amount of 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.
According to Russell L. Rothman, MD MPP, "The study showed that many patients struggle to understand current food labels, and that this can be particularly challenging for patients with poor literacy and numeracy (math) skills. Poor understanding of nutrition labels can make it difficult for patients to follow a good diet. Of particular concern are situations that involve interpretation and application of serving size. There are many opportunities for health care providers to improve how they talk to patients about using food labels and following diets. There are also opportunities for the FDA to improve how food labels are designed in order to improve how patients take care of their nutrition.
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