Food label accuracy of common snack foods

Abstract

Nutrition labels have raised awareness of the energetic value of foods, and represent for many a pivotal guideline to regulate food intake. However, recent data have created doubts on label accuracy.

Objective: We tested label accuracy for energy and macronutrient content of prepackaged energy-dense snack food products. We measured "true" caloric content of 24 popular snack food products in the U.S. and determined macronutrient content in 10 selected items.

Design and methods: Bomb calorimetry and food factors were used to estimate energy content. Macronutrient content was determined according to Official Methods of Analysis. Calorimetric measurements were performed in our metabolic laboratory between April 20th and May 18th and macronutrient content was measured between September 28th and October 7th of 2010.

Results and conclusion: Serving size, by weight, exceeded label statements by 1.2% [median] (25th percentile -1.4, 75th percentile 4.3, P = 0.10). When differences in serving size were accounted for, metabolizable calories were 6.8 kcal (0.5, 23.5, P = 0.0003) or 4.3% (0.2, 13.7, P = 0.001) higher than the label statement. In a small convenience sample of the tested snack foods, carbohydrate content exceeded label statements by 7.7% (0.8, 16.7, P = 0.01); however fat and protein content were not significantly different from label statements (-12.8% [-38.6, 9.6], P = 0.23; 6.1% [-6.1, 17.5], P = 0.32). Carbohydrate content explained 40% and serving size an additional 55% of the excess calories. Among a convenience sample of energy-dense snack foods, caloric content is higher than stated on the nutrition labels, but overall well within FDA limits. This discrepancy may be explained by inaccurate carbohydrate content and serving size.

Figure 1. Serving Size Deviation from Label

Error bars represent 95% confidence interval. The y-axis depicts serving size deviation in total grams and as % of label statements. Serving size was determined by weights of item count as shown on nutrition labels (for example: Tostitos Tortilla Chips - serving size 24 chips) and compared to the label serving size weight. Serving size was not determined for Dreyer’s Grand Vanilla Ice Cream due to the difficulty of ascertaining exactly how 1/2 cup (as the stated serving size) of ice cream should be determined. Serving size by weight (28g) as stated on the label was therefore used for further analysis. *In other parts of the country Dreyer’s Ice Cream is sold under the name Edy’s. † During the first purchase of snack products, a large bag (containing 11 serving by label) of Lays Potato Chips was purchased. Due to the difficulty of choosing 15 equally sized chips (=serving size), we excluded the data from the first run and henceforth purchased smaller bags (1 bag = 1 serving size), thus only data from the last two runs were included in the analysis. ‡ Two different flavors (Strawberry Banana Burst & Watermelon) with identical macronutrient and caloric content (by label) were used for analysis (2 each: n=4). # Product was measured 4 times (2 unprepared, 2 prepared), all data were used for analysis.

Figure 2. Deviation of metabolizable calories from label calories

Diamonds represent mean values and error bars 95% confidence interval. The Y-axis shows the difference from label calories. Open diamonds represent mean difference in total calories and closed triangles represent mean difference in % from label calories. Group means are gray shaded. The Food and Drug Administration (FDA) allows calorie content to exceed label calories by up to 20%, shown here as dashed lines. *In other parts of the country Dreyer’s Ice Cream is sold under the name Edy’s. † During the first purchase of snack products, a large bag (containing 11 serving by label) of Lays Potato Chips was purchased. Due to the difficulty of choosing 15 equally sized chips (=serving size), we excluded the data from the first run and henceforth purchased smaller bags (1 bag = 1 serving size), thus only data from the last two runs were included in the analysis. ‡ Serving size was not determined for Dreyer’s Grand Vanilla Ice Cream due to the difficulty of ascertaining exactly how 1/2 cup (as the stated serving size) of ice cream should be determined. § Two different flavors (Strawberry Banana Burst & Watermelon) with identical macronutrient and caloric content (by label) were used for analysis (2 each: n=4). # Product was measured 4 times (2 unprepared, 2 prepared), all data were used for analysis.