Net carbs vs. total carbs: What counts?

Net carbs vs. total carbs: What counts?

People often wonder if they should count their net carbohydrates or total carbohydrates, which appear on some nutrition labels. Medtronic Diabetes Clinical Manager for Cape Cod, Massachusetts, Katie Crupi-Sullivan, RD, CDE, tackles net carbs, and the advice she gives her patients with diabetes. 
 

Net carbs or total carbs: “I’m confused”
 

One of my patients recently asked me about a low carb bar her Mom had purchased for her to use as a quick snack. She wanted to know, “What is the deal with net carbs?” Net carbs was a phrase coined by the food industry when low carb diets became popular about a decade ago, and doesn’t have a formal definition. It’s not a term recognized by the Food and Drug Administration (FDA) or American Diabetes Association (ADA). 

Net carbs usually subtract fiber, sugar alcohols, and glycerin from the total carbohydrates. This can be misleading for anyone counting carbs and using insulin to carb ratio to bolus for food. 
 

When is it appropriate to subtract fiber or sugar alcohols from total carbs?
 

Looking at my patient’s pump download on CareLink, I realized when she ate the low carb bar, her blood sugar dropped. She asked, “What do I do to prevent these lows?” If you notice a low after eating high fiber foods (beans, whole grains, fiber fortified products or foods rich in sugar alcohols, sugar-free desserts and candies), there are rules set forth by the ADA:

  • When a meal has more than five grams of total fiber, you can subtract half the total fiber from the total carbohydrate
  • If a food contains sugar alcohols, you can subtract half the total sugar alcohol from the total carbohydrate

(Keep in mind that these are general guidelines and might vary for each individual so keep a close eye on your blood glucose.) 
 

What’s the deal with sugar alcohols?
 

Sugar alcohols are used in many sugar-free items and small amounts occur naturally in plant foods. When reading food labels, look for erythritol, glycerol, isomalt, lactitol, maltitol, mannitol, sorbitol, xylitol, and hydrogenated starch hydrolysates. 

Sugar alcohols are thought have a lower glycemic index and cause smaller spikes in blood sugar after meals. They have one half to one third less calories than sugar per gram, but remember, sugar alcohols are not “free” and you need to be cautious how much you’re consuming. In large quantities, sugar alcohols can cause gas, bloating, and diarrhea. 
 

Why does fiber cause my blood sugars to drop?
 

Fiber is a type of carbohydrate. On a food label, fiber is included in the total carbohydrate and it isn’t fully digested by the body. Sometimes if you eat a meal or snack high in fiber, your blood glucose may drop because the fiber is not digested. It doesn’t turn into sugar or glucose in the body. 

There are two types of fiber – soluble and insoluble. Soluble fiber dissolves in the water from your food, making a sticky liquid or gel. This gel helps trap certain food elements, slowing down digestion. Insoluble fiber adds bulk to the stool and can help food pass more quickly through the stomach and intestines. 

According to the ADA, it’s recommended women eat about 25 grams and men eat about 38 grams of fiber per day. Slowly add in fiber by increasing fruits, vegetables, beans, nuts, seeds, whole grains and oats into your diet. 
 

In the end…
 

Don’t get caught up in the latest diet trends! When managing your diabetes, keep in mind that total carbohydrate on a food label is the most important place to start.
 

Resources for carb counting

Calorie King; Free Apple App My Food Advisor

 

Guest Blogger – Katie Crupi-Sullivan, RD, CDE

Katie Crupi-Sullivan is a Registered Dietitian, Certified Diabetes Educator, and Medtronic Diabetes Clinical Manager for Cape Cod, Massachusetts. She dedicates her professional career to helping people with diabetes have a better understanding of how food affects diabetes control. She loves to educate people about advanced pump features and continuous glucose monitoring to improve diabetes management.

 

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Blog comments

Submitted by Kelley (not verified) on

In reply to by Commenter (not verified)

I'm confused AFTER reading this article! "When is it appropriate to subtract fiber or sugar alcohols from total carbs?" If more than five grams of fiber, subtract half. OTHERWISE.... don't subtract any? Subtract all?

Submitted by LOOP Blog Editorial on

In reply to by Kelley (not verified)

Hi Kelley. According to the ADA, if a meal has more than five grams of total fiber, you can subtract half the total fiber from the total carbohydrate. So if it has less than five grams of total fiber, you would not subtract anything. If the food contains any sugar alcohols, you can subtract half of the total sugar alcohols from the total carbohydrate. Please keep in mind these are general guidelines, and each person is different. Be sure to work with your healthcare team before making dietary adjustments, and keep a close eye on your blood glucose.

Submitted by John Whitehead (not verified) on

In reply to by Commenter (not verified)

I do agree wiyh much in this article. The fiber subtracting is where everything i have researched and have been taught is different. It is pretty basic that all fiber is subtracted due to the folliwing,FIber is a type of carbohydrate (just like sugars and starches) but since it is not broken down by the human body, it does not contribute any calories. Yet, on a food label, fiber is listed under total carbohydrate. So this gets kind of confusing for people who have diabetes. Carbohydrate is the one nutrient that has the biggest impact on blood glucose. So, does fiber have any effect on your blood glucose?

The answer is that fiber does not raise blood glucose levels. Because it is not broken down by the body, the fiber in an apple or a slice of whole grain bread has no effect on blood glucose levels because it isn’t digested. The grams of fiber can actually be subtracted from the total grams of carb you are eating if you are using carbohydrate counting for meal planning.

Submitted by William Sheets (not verified) on

In reply to by John Whitehead (not verified)

By Wil Sheets
I understand why they say half John, because it doesn't separate soluble fiber and insoluble so by subtracting half you are accounting for the soluble fiber

Submitted by JE (not verified) on

In reply to by Commenter (not verified)

I know this post is old but wanted to comment on a previous post. Read carefully, the FIBER in an apple does not raise blood sugar because it is not digested by the body. Don't confuse this with an apple NOT raising your blood sugar, it does have natural sugars and WILL raise blood sugar levels! I know some people may read the earlier post and comprehend it improperly, I've seen it hundreds of times. We see what we want and interpret things how we want, which isn't always correct. Great article, thanks!

Submitted by Carlos Rosado (not verified) on

In reply to by JE (not verified)

I mix apples with carrots in juicing and doesn’t raise anything on me

Submitted by J (not verified) on

In reply to by Commenter (not verified)

Can you subtract the fiber content from the carb content of an apple though?

Submitted by Nicole (not verified) on

In reply to by J (not verified)

J, you can and should subtract the grams of fiber from the total carbohydrate amount.

Submitted by Travis Alameda (not verified) on

In reply to by Commenter (not verified)

I’m newly diabetic and I am having trouble with the carb and added sugar and sugar alcohol and fiber it’s really confusing

in fasting 8 hour blood glucose it is 99 mg\d . but after 2 hour of meal rise to 150 mg\d it is no problem

Submitted by Karen Kulcsar (not verified) on

In reply to by Commenter (not verified)

I always thought you subtract fiber from carbs. Not I’m hearing only half. What is the difference between carbs and net carbs

Submitted by Nicole (not verified) on

In reply to by Karen Kulcsar (not verified)

Karen, Net Carbs is a food industry term and can be misleading for anyone counting carbs and using insulin to carb ratio to bolus for food. While our articles are helpful in understanding carbs, we do recommend speaking with your healthcare team about how you should be counting your carbs for managing your diabetes.

Submitted by William Murray (not verified) on

In reply to by Commenter (not verified)

Subtracting only half of the fiber over 5g is nonsense. Whether or not the fiber is soluble or insoluble, it is not digested by the body, so all fiber can be subtracted from total carbs. It's not as if your stomach is calculating you exceeded 5g of fiber so then it starts avoiding digestion (and then only by half!).

I have yet to have a dietician who subscribes to this calculation explain this to me: if you eat one slice of whole grain bread that has 5g of fiber and 20g of total carbs, you cannot deduct any fiber so you must count 20g of carbs. But if you eat two slices of that bread for a total of 10g of fiber and 40g of total carbs, you _can_ deduct 5g of fiber (half of the total) for a total of 30g of carbs. How does this make sense? Your stomach doesn't know it's two slices of bread vs. one slice, it's just a single meal, it only processes non-fiber carbs, period. Unless your blood sugar rises exponentially based on non-fiber carb intake, this makes no sense.


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