The Truth About Net Carbs

carb confusionTo fully understand the concept behind the terms “net carbs,” “effective carbs” or “impact carbs,” it would help to have an advanced degree in food science. It is not, however, scientists who created these terms. Food marketers invented them and have used them to great advantage in recent years to sell low “net” carb snacks and sweets, claiming that these foods have a minimal effect on blood sugar. Are the claims accurate? We can’t know. The U.S. Food and Drug Administration (FDA) has not yet set regulations for label claims about carbohydrates.

The FDA does regulate other claims about nutrient content. For a manufacturer to put “low fat” on a label, the product must contain no more than 3 grams of fat per serving and if a label says “fat free,” it can contain no more than .5 gram per serving. Sugar-related claims have rules, too. “Sugar free” means the product contains less than .5 grams of sugar per serving; “reduced” means a serving has at least 25 percent less sugar than the regular version of that food; and “no added sugar” means what it says –– the product may contain natural sugars, such as those found in fruit and milk, but any additional sweeteners are artificial.

Low-carb carbs

The idea behind the “net carb” claim is that some types of carbohydrates do not affect blood sugar and insulin the way other types do, so you can subtract these from a food’s total carbohydrate count. For instance, the carbohydrates in potatoes, bread, and white rice are converted almost instantly into glucose and hit the bloodstream fast. But carbohydrates such as the fiber found in whole grains, fruit, and vegetables are absorbed slowly and much of it is not digested at all. The American Diabetes Association condones subtracting grams of fiber from a food’s total carb count when it contains 5 or more grams of fiber.

Other carbs that fall into this category are glycerin and sugar alcohols. Sugar alcohols are artificial sweeteners that contain about half the calories of sugar and have a lesser impact on blood sugar. These include mannitol, sorbitol, isomalt, lactitol, and xylitol, among others. Many diabetes educators say you can subtract half the grams of sugar alcohols in a food from the total carbohydrates, but it’s important to test your own reaction to any food containing sugar alcohols because blood sugar responses to each kind can vary widely from person to person. Keep in mind, too, that sugar alcohols can cause gastrointestinal upset. Glycerin, which is often added to foods for moisture and texture, is also only partially digested, but its effects on blood sugar vary as well.

“False and misleading”

Although the FDA has yet to lay down the law, which will clear up at least some of the confusion, one company did get a slap on the wrist last year for calling its product “zero carb,” when it was actually zero “net” carbs. In a warning letter, the FDA told the company that “the claim ‘zero carb’ would be false and misleading on this product label if the product does not contain less than 0.5 grams of total carbohydrate (including fiber)…” The next step is for the FDA to mandate whether and how the “net” carb claim can be used on labels.

The bottom line is that these foods may not be as innocuous as they seem, in terms of blood sugar impact, and most are far from healthy choices. So go easy, test your own response, and then mentally file these products in your “occasional treat” category.

Reviewed by Susan Weiner, R.D., M.S., C.D.E., C.D.N. 3/08

Last Modified Date: November 28, 2012

All content on is created and reviewed in compliance with our editorial policy.

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by Brenda Bell
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