The Alert Consumer

Food labels have a lot of technical information that is hard to interpret. We will compare the nutrition labels of raw sunflower seeds from two stores to try to figure out the differences. Weight ratios of fat, carbohydrate, and protein of 2:1:1 to 3:1:1 are very typical for nuts and oil seeds.

The most obvious discrepancy in these labels is the serving size of 28g for the Whole Foods seeds vs. 33g for the Trader Joe’s seeds, both of which have 190 Calories per serving. It is unlikely that a five-gram (15%) difference in the serving size would have a negligible effect on the total calories. We also notice that the Whole Foods seeds have three times the amount of fiber as the Trader Joe’s seeds, and Trader Joe’s seeds have no sugars whereas the Whole Foods seeds have 1 gram of sugars. Aren’t all sunflower seeds the same? How reliable are these “Nutrition Facts”?

Let us start with a simple check to see if everything adds up. The Whole Foods serving size is 28g, but if we add 17g of fat, 6g of carbohydrate, and 7g of protein the total is 30g. Oops! It is not unusual for the sum of the components to be slightly different than the whole due to rounding errors and unlisted components, but it is abnormal to have the components exceed the total serving size by 2 grams (7%).

The Trader Joe’s serving size is 33g. Adding 16g of fat, 8g of carbohydrate, and 8g of protein we get 32g. This is much more consistent and the discrepancy is probably due to rounding. If we had 16.3g of fat, 8.4g of carbohydrate, and 8.3g of protein everything would add up properly, but by rounding to whole numbers we would lose 3% precision.

How about the Calories? Fat has 9 Calories per gram, and protein and carbohydrate have 4 Calories per gram. Fiber contributes no calories because it cannot be digested, so we subtract the grams of fiber from the total carbohydrate. The remaining carbohydrates consist of sugars and starches. The Whole Foods seeds have 9×17 + 4×(6-3) + 4×7 = 193 Calories. The Calories from fat are 9×17 = 153. By rounding to the nearest ten, we get 190 total Calories and 150 Calories from fat in perfect agreement with the label.

Trader Joe’s seeds have 9×16 + 4×(8-1) + 4×8 = 204 Calories. The Calories from fat are 9×16 = 144. By rounding, we get 200 total Calories and 140 Calories from fat. Oops! Something is inconsistent. The total Calories calculated from the components is 5% larger than stated on the label, and the Calories from fat calculated from the components is 6% lower than on the label.

The % Daily Values are based on a U.S. government recommendation that 30% of the Calories should be from fat, 55% from carbohydrates, and 15% from protein. For a 2000-Calorie diet, this is equivalent to 67g of fat, 300g of carbohydrate that includes 25g of dietary fiber, and 75g of protein per day. The dietary fiber for the Whole Foods seeds should be 3×100/25 = 12% instead of 13%. Trader Joe’s Total Fat should be 16×100/67 = 24% instead of 25%, and the dietary fiber value should be 1×100/25 = 4% instead of 5%. These differences are not significant.