Do You Know How to Calculate Net Carbs?

Counting carbs can get tricky. Did you know that fibre is a type of carbohydrate? And do you know if you should include sugar alcohols like erythritol or xylitol? Let’s clear out the confusion.

There are a lot of different types of carbs

We learned how many carbs you should eat if you want to be low carb or keto in a previous article. The thing is counting carbs can be tough. When you hear the word carbs you probably think of things like sugar, rice, or potatoes. Those are digestible carbs. They give you calories, elevate your blood sugar and raise your insulin levels. That’s why you’re trying to limit those.

Fibre is another type of carbohydrate but it’s not digestible. That means it won’t affect your blood sugar or insulin, and it won’t give you any calories. It passes through your body, helps your digestion, and feeds friendly bacteria in your gut. It’s beneficial and most of us should eat more of it.

The trickiest group are polyols, also called sugar alcohols. These are sweeteners like maltitol, sorbitol, erythritol, or xylitol. They are somewhere in the middle. They are partially digestible and their caloric content and effects on insulin vary as a result.

Note: The word "alcohol" is a part of the name but don’t worry, sugar alcohols do not contain any ethanol so they don’t act like alcohol in your body. They won´t make you drunk.

How do you know which ones to count into your carb intake?

This is where net carbs can help! Net carbs tell you the total amount of digestible carbs your food contains. Fibre is not calculated and sugar alcohols are only calculated partially, depending on which one you choose.

Most sugar alcohols are about 50 % digestible. Erythritol is an exception. About 90% of it is absorbed in the small intestine and then excreted in the urine (1). The remaining 10% passes unfermented through the colon (2). This means you don’t have to count erythritol in your carb intake at all. It also doesn’t impact your insulin levels (3).

So, if you want an equation it would look something like this:

Net carbs = total carbs – fibre – sugar alcohols (+ half of all sugar alcohols that are not erythritol)

Don’t focus on counting carbs too much

It is good to know where you stand on net carb intake. It can help people who use insulin avoid hypoglycaemia. It’s also a good way to learn about food to expand your range of choices and increase fibre intake. But don’t obsess over it. Counting carbs can never be 100% accurate. There will always be individual differences in digestion and food preparation. Plus, it can create a false sense of security which leads people to overindulge on sugar free and low carb treats. Always keep your diet balanced and rich in whole foods no matter the number of carbs!

What’s the takeaway? It’s simple, focus on choosing foods that are low in digestible carbs and rich in fibre. And if you go for sugar alcohols as a sweetener make sure it’s erythritol. You can count on Lizza that all bestsellers fit this description!


  1. Geoffrey Livesey (2003): “Health potential of polyols as sugar replacers, with emphasis on low glycaemic properties”, in: Nutr Res Rev.
  2. Eva Arrigoni et al. (2005): “Human gut microbiota does not ferment erythritol”, in: Br J Nutr.
  3. M Ishikawa et al. (1996): “Effects of oral administration of erythritol on patients with diabetes”, in: Regul Toxicol Pharmacol.

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