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Eating with Diabetes: Counting ''Net'' Carbs

Since low carbohydrate diets became popular, the phrase "net carbs" has become a fairly regular fixture on the labels of food products. But, if you are not familiar with the term you may be wondering what in the world it means!

There are three types of carbohydrates: starches, sugars and fiber. All three types of carbs are added up and listed as Total Carbohydrates on the Nutrition Facts Label of a food product.

The concept of net carbs is based on the fact that, although it is considered a carbohydrate, dietary fiber is not digested the same way the other two types of carbohydrates (starches and sugars) are. While starches and sugars are broken down into glucose (blood sugar), fiber isn't treated the same way. The fiber you eat passes through the body undigested and helps add bulk to your stool (among other benefits). The indigestibility of fiber is where the idea of "net carbs" comes in. In fact, sometimes, net carbs are sometimes referred to as "digestible carbs.''

In recent years, food manufacturers have started including net carbs in addition to total carbs when labeling products. Many foods proudly display net carbs on their labels to entice both low-carb diet fans and people with diabetes.

While the concept of net carbs can be utilized in diabetes meal planning, read labels with a discerning eye. At present there are no mandated rules for calculating or labeling net carbs on food packages. The FDA does not regulate or oversee the use of these terms, and exactly what is listed as "net carbs" can vary dramatically from product to product. Some products calculate net carbs as total carbohydrates minus dietary fiber, other labels reflect net carbs as total carbohydrates minus dietary fiber minus sugar alcohols, and still others calculate net carbs as total carbohydrates, minus dietary fiber minus sugar alcohols minus grams of protein.

Many packaged foods that are marketed as high in fiber low in carbs actually add extra fiber, such as inulin, polydextrose and maltodextrin, to food products to lower the net carb serving. Most nutrition experts agree that these "stealth fibers " do not have the same health benefits and may not have the same benign affect on blood sugar levels as foods that contain naturally occurring fiber. As you can see, the whole issue of "net carbs" can get tricky very fast. And for people with diabetes, for whom carbohydrate counting and blood glucose control is a serious issue, referring to net carbs on a food label can have serious consequences.

However, counting net carbs can work for people with diabetes who use a meal-planning technique known as carbohydrate counting to help balance their blood sugar levels—when done correctly.

Here's how a person with diabetes can count net carbs safely and effectively:
  • The food in question must contain at least 5 grams of dietary fiber in the serving size you are planning to eat.
  • Read the Nutrition Facts label or look up the nutrition facts of the food to find both the total carbohydrates and total fiber for the serving size you plan to eat.
  • Subtract HALF the total grams of fiber from the total grams of carbohydrates to calculate the net carbs in your food serving.
  • Always perform this calculation yourself and do not rely on "net carb" totals listed on any food label.
Take the following example (see food label, left):

This product has 5 grams of dietary fiber, which means you can subtract half that amount (2.5 grams) from the total carbohydrate (23 grams) to calculate net carbs, which equals 20.5 grams per serving.

The whole point of counting net carbs versus total carbs is to allow someone to eat more of a carbohydrate-containing food without adversely affecting their blood sugar levels. If you find the issue of net carbs confusing, don't worry about it. There is no reason to use this technique if counting total carbohydrates works well for you. Both options can work as long as you are doing them correctly and reading "net carb" labels with a discerning eye.

For more specific information or help, talk to your health care provider. The American Diabetes Association's National Call Center also offers live advice from 8:30 a.m. to 8 p.m. EST, Monday through Friday at 1-800-DIABETES or 1-800-342-2383.
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Member Comments

Very informative, thank you. I had never heard of the 5 g and divide by 2 rule. Report
Fiber , fiber , fiber. Report
When we had a diabetes class they mentioned the above 5 grams of fiber dividing it by 2. I've been doing that for quite some time now. Good article! Report
Keep,those carbs down. Protein up, fiber up. Report
Informative article!
So much to learn about label reading Report
Thank you for the information. I think the USDA needs to regulate standards for all foods. What are we paying them for? just like most government agencies. So much work, so many workers and an unstable political climate. The average tax payer (you and I) are forgotten whilst the spend time complaining and covering their azz they accomplish little or no work for us. Advertising seems to me to be all lies falling far beyond "puffing" (which is legal). Sometimes this confusion is detrimental to consumers. This is what we pay the govt. for "to keep us safe" Report
Thanks for an informative article :) Report
How does SP track net carbs -- it's on optional nutrient to add to the food tracker Report
Keep in mind the following: It is in the US (only, I think?) that the carbs need to be subtracted to get your net carbs. In Europe, and Oz, and maybe other countres, fibre is already subtracted on the nutrition label. Report
Thanx for the good info -- bonus: more ways to practice our math skills! Report
I've read this article before, but I needed to refresh my memory. I hope everyone has a Super & Blessed Saturday! Report
Very concise explanation. Report


About The Author

Amy L. Poetker
Amy L. Poetker
Amy Poetker is a licensed and registered dietitian and certified diabetes educator with a master's degree in dietetics. Amy, who has spent most of her career working in diabetes education, is dedicated to the treatment of that disease and the prevention of related complications. See all of Amy's articles.
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