September 29, 2006

Poor math skills feed food label confusion: study

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Accurately deciphering food label information is a struggle for some people, according to a study by Russell Rothman, M.D.
Photo by Anne Rayner

Poor math skills feed food label confusion: study

If you've ever struggled to decipher the nutrition information on food labels, you're not alone. In fact, the confusion aisle at the supermarket is getting pretty crowded these days.

According to a study by researchers at Vanderbilt University Medical Center, difficulties with math and reading are significantly limiting people's ability to adequately understand the information presented on food labels.

The study, which will be published in the November issue of the American Journal of Preventive Medicine, involved 200 primary care patients from a wide socioeconomic range. Among the findings:

• Two-thirds of patients surveyed could not correctly calculate the amount of carbohydrates consumed in a 20-ounce bottle of soda that had 2.5 servings in the bottle.

• Just over half could calculate the number of carbohydrates in half of a bagel, when the serving size on the label was listed as a whole bagel.

• Only 22 percent could determine the net carbohydrates in two slices of low-carb bread, and only 23 percent could determine the net carbohydrates in a serving of low-carb spaghetti.

“The study demonstrates that patients can have many difficulties interpreting current food labels, and their performance is highly correlated with their underlying literacy and numeracy (math) skills,” said Russell Rothman, M.D., assistant professor of Medicine and Pediatrics.

Researchers found that even patients with higher levels of education can struggle to interpret current food labels, particularly in situations that involve interpretation and application of serving sizes.

“We found that, while a lot of the people we tested had decent literacy skills, many of them had poor numeracy skills. I think that many people in this country find math to be very intimidating, and they don't like to deal with things that have numbers,” Rothman said.

Correctly interpreting food label information is especially critical for people with chronic illnesses for which specific dietary intervention is required, such as diabetes and hypertension.

Many patients had difficulty applying serving size information, made calculation errors, or were confused by extraneous information on the food label. Also troubling were situations that involve interpretation and application of serving-size information.

These errors can lead to both over-estimation and under-estimation of the amount of calories and nutrients consumed.

The study's results suggest there may be important opportunities for health care providers and the Food and Drug Administration (FDA) to improve nutrition education and food labels to increase patient understanding of this information.

“Future studies should examine the optimal design of food labels and the role of improved patient/provider communication to enhance patient comprehension and behavior,” Rothman said.

The FDA is currently considering changes to food labels to improve comprehension. In this study, the authors propose five possible food label changes that merit further study:

• Improve highlighting of the serving size and servings per container;

• For smaller items, present nutrient information for the entire container (for example, a 20-ounce bottle of soda should not be listed as having two and a half servings);

• Consider presenting information for several possible servings of a product (for example, horizontal lines on a pint of ice cream with the label stating “if you eat to here, you have consumed this many calories, carbohydrates, fat and other nutrients);

• Remove information that few people seem to understand and is a constant source of confusion or misinterpretation, such as percent of daily value information and the footnote of recommended daily values;

• Indicate more clearly the net carbohydrates and how it is defined. Given the popularity of carbohydrate-related diets and food options, this information could be placed in a carbohydrate section of the label.