What Are Indigestable Carbohydrates?

“Carbohydrate” is an umbrella term that includes everything from table sugar to the cellulose found in wheat bran. We are well adapted to make use of carbohydrates for energy and have enzymes that chop up large carbohydrates into their individual sugar subunits. This is why eating a meal with lots of starch, such as pasta or pizza, will lead to an increase in blood sugar.

Foods containing digestible carbohydrates can be placed on a spectrum of ‘simple’ to ‘complex’ based upon the types of carbohydrates they contain and what other molecules are in the food. For example, a soda simply containing carbonated water, color, flavor, and sugar will fall at the extreme ‘simple’ end of the spectrum because the sugars in the drink are small and will be rapidly absorbed into the blood. Whole wheat bread, on the other hand, is a complex carbohydrate: Even though it contains starch, which will be broken down into sugar and absorbed, the other molecules (like protein and indigestible carbohydrates) and its structure ( literally being trapped in part of the grain) make it difficult for digestion enzymes to access the carbohydrates. This delays the release of sugar from complex carbohydrates.

Indigestible carbohydrates, often lumped together under the term ‘fiber’, are fundamentally different from digestible carbohydrates. Indigestible carbohydrates cannot be turned into glucose and absorbed because our bodies lack the enzymes necessary to digest them.

For this reason, consumers are encouraged to read the Nutritional Information panel and do some simple math: Subtract the grams of ‘fiber’ from the grams of total carbohydrate. The remaining amount is the net digestible carbohydrate. In other words, this is the amount of carbohydrate that will be digested and turned into glucose.

Consider the following example: A 60g serving of white bread contains 28g of carbohydrates and 1g of fiber (indigestible carbohydrate), meaning that it provides 27g of digestible carbohydrates. The same 60g serving of whole wheat bread contains 28g of carbohydrates and 4g of fiber (indigestible carbohydrate), meaning that it provides 24g of digestible carbohydrate. Eating the serving of whole wheat bread gives you the same sense of fullness with 11% fewer digestible carbohydrates.

Some indigestible carbohydrates, known as prebiotics, offer added benefits. These fermentable fibers fuel the healthy bacteria in our gut microbiome, which then produce nutrients and factors that influence how our body processes food. Prebiotic fermentation can increase levels of GLP-1, a potent blood sugar lowering hormone.

In conclusion, eating a high-fiber diet can help individuals manage high blood sugar in three different ways: First, by letting you eat the same serving size of food while consuming fewer digestible carbohydrates. Second, by releasing glucose more slowly and, therefore, increasing blood sugar levels more gradually. Third, by promoting a healthy gut microbiome, which interacts with your body to help it respond more effectively to rising levels of blood sugar. Increasing the abundance of indigestible carbohydrates in your diet is therefore an effective, all-natural strategy for helping to keep blood sugar levels within a healthy range.