Whether to count net or total carbs is a controversial topic within the low-carb community.
For starters, the term “net carbs” isn’t officially recognized or agreed upon by nutrition experts. In addition, due to conflicting and outdated information, figuring out how to calculate net carbs can be confusing.
In fact, the net carb claims on packaged foods may not reflect the number of carbs your body actually absorbs.
Luckily, knowing how your body processes different types of carbs may help you achieve your target blood sugar, weight loss and health goals.
This article looks at the science behind net carbs, provides simple calculations for determining your intake and discusses the pros and cons of counting net carbs.
What Are Net (Digestible) Carbs?
Simple carbs contain one or two sugar units linked together and are found in foods like fruits, vegetables, milk, sugar, honey and syrup.
Complex carbs contain many sugar units linked together and are found in grains and starchy vegetables like potatoes.
When you eat a carb-containing food, most of the carbs are broken down into individual sugar units by enzymes produced in your small intestine. Your body can only absorb individual sugar units.
However, some carbs can’t be broken down into individual sugars, whereas others are only partially broken down and absorbed. These include fiber and sugar alcohols.
Because of this, most fiber and sugar alcohols can be subtracted from total carbs when calculating net carbs.
Summary: Net (digestible) carbs are broken down into individual sugar units and absorbed into your bloodstream. However, your body processes fiber and sugar alcohol carbs differently than digestible carbs.
How Your Body Handles Fiber Carbs
Fiber is a unique form of carbs in terms of its digestion and effects on your body.
Unlike starch and sugar, naturally occurring fiber isn’t absorbed in your small intestine.
This is because the links between sugar units can’t be broken down by the enzymes in your digestive tract. Therefore, fiber passes directly into the colon (1).
However, its fate after that depends on what type of fiber it is.
There are two broad categories of fiber: insoluble and soluble. About two-thirds of the fiber you eat is insoluble, while the other third is soluble.
Insoluble fiber does not dissolve in water. It creates a bulkier stool and can help prevent constipation. This type of fiber leaves the colon unchanged, provides no calories and has no effect on blood sugar or insulin levels (2).
By contrast, soluble fiber dissolves in water and forms a gel that slows down food’s movement through your system and can help make you feel full (3).
After arriving in your colon, soluble fibers are fermented into short-chain fatty acids (SCFAs) by bacteria. These SCFAs help keep your gut healthy and may also provide a number of other health benefits.
Since about one-third of the fiber in most foods is soluble, a serving of food containing 6 grams of fiber would contribute up to 4 calories in the form of SCFAs.
However, while soluble fiber does provide a few calories, it doesn’t seem to increase blood glucose. In fact, the most recent research suggests that its effects in the gut help reduce blood sugar levels (6, 7).
Recently, several food manufacturers replaced IMO with other forms of fiber in their products. However, IMO can still be found in a number of “low-carb” foods.
Summary: Naturally occurring fiber is not absorbed in the small intestine. Gut bacteria ferment soluble fiber into SCFAs, which contribute minimal calories and have neutral or beneficial effects on blood sugar.
How Your Body Handles Sugar Alcohol Carbs
Sugar alcohols are processed similarly to fiber, with a few important differences.
Many sugar alcohols are only partially absorbed in the small intestine, and there is a lot of variation among different types.
Researchers report the small intestine absorbs 2–90% of sugar alcohols….