Deciphering Food Nutrition Labels a Heavy Task for Many

September 26, 2006

NASHVILLE, Tenn. -- Many patients haven't a clue about the meaning of the dietary information in food labels, researchers here reported.

NASHVILLE, Tenn., Sept. 26 -- Many patients haven't a clue about the meaning of the dietary information in food labels, researchers here reported.

The dietary information from labels may be well beyond patients' math skills in particular, reported Russell Rothman, M.D., of Vanderbilt University here, and colleagues, in an online study in the November issue of the American Journal of Preventive Medicine.

Poor label comprehension correlated highly with low-level literacy and numeracy skills, but even patients with better reading skills could have difficulties interpreting labels, they found.

In a cross-sectional study from June 2004 to April 2005, 200 primary-care patients (mean age 43, 72% women) from a wide socioeconomic range, filled out a Nutrition Label Survey, designed with input from registered dietitians, primary care physicians, and authorities in health literacy and numeracy.

The standardized tests for reading and math skills were the Rapid Estimate of Adult Literacy in Medicine (REALM) and the Wide-Range Achievement Test, third edition (WRAT3). Of the patients, 68% had at least some college education, while 75% had at least a high school education.

Superficially, most patients (89%) felt the food labels were a snap. Yet on average, only 69% (standard deviation 21%) of the patients answered food-label questions correctly. And broken down, even that figure turned out to be misleading.

Reading ability was far better than math facility. Of the patients, 77% had at least ninth-grade reading skills, but only 37% had ninth-grade math skills, and the test results reflected the math deficiency.

For example, only 32% of the patients could calculate the number of grams of carbohydrate (67.5) consumed from a 20-ounce bottle of soda that contained 2.5 servings (total carbohydrates per serving = 27 g.).

In addition, only 60% of patients could determine the number of carbohydrates consumed if they ate half a bagel, when the serving size was a whole bagel.

Calculating net carbohydrates was another obstacle. Only 22% of patients could determine the net carbohydrates in two slices of low-carb bread, and only 23% could determine the net carbohydrates in a serving of low-carb spaghetti.

In a summary of the nutrition questionnaire errors, the researchers said there were 970 errors in the subjects' responses to the first 12 items. Common errors included misapplication of the serving size (n=325), confusion due to extraneous material on the food label (n=369), and incorrect calculation (n=276).

Higher comprehension of food labels was significantly correlated (all P values

Some of the researchers' suggestions were:

  • Doctors need to be careful, for example, about asking a patient with hypertension or heart failure to limit sodium intake to 2 g if the patient cannot accurately interpret food labels.
  • Speak clearly and concisely, avoid jargon, set realistic goals, and use low-literacy-oriented material to help comprehension.
  • Asking patients to "teach back' information to confirm understanding may also help.
  • The use of clinical educators, such as registered dietitians, who have resources and training to educate patients with low literacy or numeracy skills, may be beneficial.

In a summary of the study's limitations, the researchers mentioned that as in all cross-sectional studies, the results can show associations but not causation. Patients' performance may have been inflated by the survey design, which permitted 50-50 guessing on 12 of the questions. Greater deficits in label comprehension might have been shown if the survey had been given to a broader population, they said.

Finally, they authors said, at this point they do not know whether patients misunderstanding of nutrition labels actually translates to poorer dietary habits or worse clinical outcomes.

The results of this study suggest that there may be important opportunities for healthcare providers and the FDA to improve nutrition education and nutrition labels, Dr. Rothman said.

"Future studies should examine the optimal design of food labels and the role of improved patient-provider communication to enhance patient comprehension and behavior," he concluded.

Included in the funding support for this study was an award from the Pfizer Clear Health Communication Initiative.