You’ve probably read the nutrition labels of various food items and seen carbohydrates and sugars, but you may have also heard about net carbs. These aren’t displayed on the label, but what exactly are they and how could they affect your digestion, blood glucose and absorption of carbohydrates?

Different Carbohydrates

On food labels, we have protein, fat, carbohydrate, fibre, sugar and salt content. Of these molecules, carbohydrates, fibre and sugar are all carbohydrates. Fibre is carbohydrate which the body cannot digest and passes through the intestinal tract mostly undigested and comes out of the body within stools. Sugars are the simplest forms of carbohydrate available to the body and are most readily absorbed by the body. These include monosaccharides and disaccharides. Carbohydrates refer to all sugars and longer chain carbohydrate molecules such as oligosaccharides and starches (think potatoes).

What Are Net Carbs?

Net carbs are the number of grams of carbohydrate which have an impact on your blood sugar and insulin. Despite being a carbohydrate, fibre has no effect on blood glucose or insulin and can even slow down the rate at which passes through the gastrointestinal tract resulting in lower postprandial blood glucose and insulin levels which will be particularly useful in individuals with hyperglycemia.

You can easily calculate net carbs using the following equation:

Net Carbs (g) = Carbohydrates (g) – Fibre (g) – Sugar Alcohols (g)

For example, one medium apple contains:

  • 0.3g fat
  • 0.5g protein
  • 25g carbohydrates
  • 19g sugars
  • 4.4g fibre
  • 0g sugar alcohols
  • 25g carbohydrates – 4.4g fibre = 20.4g net carbs

This gives a simple way of figuring out the potential impact of the consumed carbohydrates on your blood glucose and insulin rather than looking at total carbohydrates as a whole figure. Low glycemic index carbohydrates tend to be high in fibre which is why they elicit a lesser blood glucose spike than high glycemic index carbohydrates which tend to be low in fibre.

Most people interested in net carbs are generally following a keto diet or are curious about the impact carbohydrates have on blood glucose. Those on a keto diet may find that they can actually consume more carbohydrates if more carbohydrates come from fibre resulting in a lower number of net carbs consumed.

Net Carbs On A Keto Diet

Whilst people on a keto diet will try to consume fewer carbohydrates, it could be more accurate to look at the net carbohydrates consumed since fibre isn’t digested by the body. This could allow someone trying to adhere to a maximum of 50g net carbohydrates per day to consume 70g total carbohydrates including fibre. The fibre could certainly beneficial to include due to the slowed gastric emptying in the intestines so glucose is released more slowly into the bloodstream.

If you’re consuming fibrous vegetables on a keto diet, usually the fibre makes up a large amount of the carbohydrate content making them a more ideal source of food to consume on a keto diet without worrying too much about carbohydrate count. When it comes to leafy green vegetables, the carbohydrate count is so minimal that it’s hardly worth taking them into the equation.

Net Carbs And Sugar Alcohols

Like fibre, sugar alcohols (mostly used as artificial sweeteners) cannot be properly digested by the body and pass through undigested although sometimes a minimal amount is absorbed. These sugar alcohols are designed to give sweetness to food without adding sugar and since they aren’t digested they have no effect on blood glucose and insulin.

They aren’t found in meat, fruit or vegetables but are added to sodas, protein and other processed foods to make them sweeter whilst adding less sugar to them. One good example of this is low-carb protein bars. As they aren’t absorbed by the body, these also need to be deducted from total carbohydrates when calculating net carbs.


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Further Reading:

The Role Of Fibre In The Body

What Is The Glycemic Index