How do low-digestible sweeteners behave in our bodies?

Low-digestible sweeteners provide fewer calories than sugar because they resist digestion—some to a greater extent than others. Here's how our bodies process them:

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• Absorption in the small intestine:
  They're either incompletely absorbed or not absorbed at all in the small intestine. For example, allulose is completely absorbed.
  Erythritol has a fast and partial (60 to 90 % of ingested erythritol) absorption, while xylitol is absorbed slowly and in smaller amounts (only 1/4 of the ingested amount).
   

•  Metabolism:
  Some of these sweeteners are slowly digested, while others undergo only partial metabolism.
  
  For instance, allulose is not significantly metabolized. Erythritol isn't metabolized — though a small portion passes intact into the large intestine. Since allulose and erythritol are not converted into glucose, they have no effect on blood sugar levels.
  
  On the other hand, xylitol is slowly absorbed and converted into glucose, so it does not cause a sudden increase in blood sugar. 
   

• Fermentation in the large intestine:
  The portion that is not digested by gut enzymes reaches the large intestine, where they may be fermented by the microbiota (healthy bacteria in the gut).
  
  This fermentation has both drawbacks and benefits. It can cause digestive issues such as bloating, flatulence, and diarrhea. However, they may act as prebiotics, by stimulating the growth and activity of gut microbes, or as a fiber by improving bowel function. 
   

• How come some sweeteners are not digested and still have calories?
  Even though we cannot metabolize some of these sweeteners—like erythritol—bacteria in the lower digestive tract can. The low caloric value attributed to them is because microbes metabolize them, and we obtain their energy indirectly.
  
  This is why allulose and erythritol fit into two categories of sweeteners — "low-digestible" and "zero-calories".
   

Covered Elsewhere:

Even though allulose and erythritol are low-digestible carbohydrates, you'll find them with zero-calorie sweeteners instead because they provide almost 90 percent fewer calories than table sugar and so, can be labeled as zero-calorie. Refer to my Allulose Buying Guide or Erythritol Buying Guide to learn more. 

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How many calories in low-digestible sweeteners?
Low-digestible sweeteners provide 3 or fewer calories per gram, as opposed to 4 cal/g for sugar. In practical terms, that’s less than 12 calories per teaspoon compared to sugar’s 16 calories per teaspoon.​

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Do low-digestible sweeteners affect blood sugar levels?

When it comes to the effect on blood sugar levels, low-digestible sweeteners may act in one of two ways:

 

1. Partially or slowly digested
   Polyols like sorbitol and xylitol are carbohydrates that break down slowly during digestion, releasing glucose slowly in the bloodstream, not causing a sudden increase in blood sugar. The glycemic index (GI) is the potential carbohydrates have to increase blood glucose levels, so polyols offer a low GI (9 for sorbitol and 7–8 for xylitol).
    

2. Not digested at all
   Eryhtritol and allulose are not metabolized into glucose. Having no effect on blood glucose, their GI = 0.​​​