What Are “Net Carbs”?
I am finding that some products list “net carbs,” which is different from the grams of carbohydrates listed in the nutrition label. Which should I use as a guide to calculate my insulin dosage? Raymond Edwin, Freeville, New York
Madelyn L. Wheeler, MS, RDN, FADA, FAND, CD, responds
The term “net carbs” doesn’t have a legal definition, so when you see it on a food package, always read the nutrition facts and ingredients list for more information.
What to Know
The label “net carbs” was first seen on food packaging during the low-carb craze years ago. It is a marketing method used by food companies to indicate that their products might contain less carbohydrate than could be designated in the nutrition facts. Companies define “net carbs” as the total grams of carbohydrate minus the grams of sugar alcohols, fiber, and glycerin. But this equation isn’t entirely accurate because some of the sugar alcohols and fiber are absorbed by the body and can affect blood glucose.
Find Out More
Scientists determine a food’s total carb count by subtracting the grams of protein, fat, moisture, and ash from a food’s total weight. For food labeling purposes, the Food and Drug Administration (FDA) requires that labels list the full number of grams of total carbohydrate that come from sugar alcohols and fiber. But these sources of carbohydrate are only partially converted to glucose—or not converted at all—so they may have less impact on blood glucose than other carbohydrate components.
On average, the body converts about half of the grams of sugar alcohols into glucose. The exception is erythritol; none of it is converted to glucose. Total fiber is made of various types of natural fibers and manufactured ingredients, which differ as to whether they are digested and how they affect blood glucose. While no general statements can be made about fiber, insoluble fiber (found, for example, in high-fiber cereals) is not considered by the FDA to be absorbed and converted to glucose.
According to an American Diabetes Association nutrition position statement, most people don’t need to subtract grams of fiber or sugar alcohols from total carbohydrate when carb counting. However, if you’re on intensive insulin therapy and manage your diabetes with an insulin-to-carb ratio, you may decide to subtract all insoluble fiber grams and half of all sugar alcohol grams from total carbohydrate to determine the carb in your calculations.