The Food and Drug Administration (FDA) requires that the packaging of every manufactured food product display certain information. Ingredients must be listed in descending order of weight. Labeling must also include a "Nutrition Facts" panel. Unfortunately, such labels do not supply all the facts, especially when it comes to carbohydrates. Nonetheless, it is important to learn how to read them—and interpret them.
Backing Into a Carb Count
Almost everything displayed on the Nutrition Facts panel is based on assays, regulated by the FDA. The quantity of fat, protein, ash and water can be directly and exactly assayed. (Water and ash need not be listed on nutrition panels.) Carbohydrates, however, are the exception. Instead, the amount of carbohydrate is arrived at only after the above four components are directly computed. In other words, what is not fat, protein, ash or water is grouped together as carbohydrate.
All Carbs Are Not Created Equal
To complicate matters still further, carbohydrates are comprised of several subgroups, which include dietary fiber, sugar, sugar alcohols and other carbohydrates—a kitchen-sink grouping of gums, lignans, organic acids and flavenoids. (These individual items can be assayed.) The FDA requires that a nutrition label include the total number of grams of carbohydrates. The amount of dietary fiber and sugar must also be listed. However, the law does not require that other carbohydrate subcategories appear. Some manufacturers voluntarily include the subcategories of sugar alcohol and “other carbohydrates.”
Not all types of carbohydrates behave the same way in the body. For example, when table sugar is digested, it turns it immediately into blood sugar. Other carbs, such as sugar alcohols, have a minimal impact on blood-sugar levels; still other carbs, such as dietary fiber, pass through the body without any impact on blood sugar level. To date, the FDA has not focused on these important biochemical differences and treats all carbohydrates alike.
The Impact on Blood Sugar
Food labels don’t give a number for the carbs that impact blood sugar, known as Net Carbs or impact carbs. Fortunately, they’re easy to ascertain. To calculate the carbohydrates that count, simply subtract the number of grams of dietary fiber from the total number of carbohydrate grams. In the case of low-carb products, also subtract the grams of sugar alcohols, including glycerin.
What Is a Serving?
There is another rather sneaky aspect of nutrition labels. For example, a 20-ounce bottle of flavored ice tea sweetened with corn syrup—definitely unacceptable on Atkins—would appear to be one serving, but look carefully at the Nutrition Facts panel and it’s clear that a single serving is calculated not as the 20 ounces in the bottle but as 8 ounces. That means that all those calculations about carbohydrate content, sugar content and calories are for only less than half the whole bottle. Most consumers are unaware of this mixed message about serving size. Even with acceptable foods, if more than what is considered one serving is consumed, it’s necessary to multiply the adjusted carb count by the appropriate number of servings.