Both dietary fiber and sugar alcohols are thought to have little or no impact on blood sugar, which is why those numbers aren’t included in a net carb count.
Fiber
Dietary fiber is a type of carbohydrate that the human body does not digest. It’s considered extremely healthy, and is mainly found in fruit, grains, legumes, and vegetables, especially when they are minimally processed. In theory, it has no impact on blood sugar.
“While fiber may not impact blood sugar directly, the idea for including fiber in meals is to allow for a more blunted response versus a straight spike or rise in blood sugar,” says Kimberlain. “In general, the more fiber a meal contains, the better.”
There are two types of dietary fiber: soluble and insoluble fiber. Soluble fiber feeds good gut bacteria, and is found in foods such as apples, barley, and oats. Insoluble fiber helps promote softer and regular stools, and is found in foods such as whole-wheat flour, vegetables, and berries.
Sometimes food packaging lists the amount of each of these different fibers, but sometimes it does not. Both types of fiber are believed to help lower blood sugar levels in the long-term, but you may find that your body tolerates one type of fiber better than the other.
Sugar Alcohols
Sugar alcohols are used as an alternative sweetener in many packaged low-carb foods. They can occur naturally in foods, but most are produced industrially.
Foods that are labeled “sugar-free,” including hard candies, cookies, chewing gum, and soft drinks may contain sugar alcohols.
Sugar alcohols are carbohydrates that are hybrids between sugar molecules and alcohol molecules. They are generally thought to have zero calories and zero blood sugar impact. Examples of sugar alcohols include:
- Sorbitol
- Xylitol
- Lactitol
- Mannitol
- Erythritol
- Maltitol
Sugar alcohols are converted to glucose more slowly than other types of carbohydrates, and they require little to no insulin to be metabolized.
“This creates a minimal impact on blood glucose,” says Lori Zanini, RD, CDCES, a certified diabetes care and education specialist based in Los Angeles, and author of Eat What You Love Diabetes Cookbook. “When calculating net carbs, individuals can subtract half or all of the amount of sugar alcohols from the total carbohydrates.”
In many ways, sugar alcohols such as erythritol are attractive alternatives to sugar and often quite helpful in supporting people’s health and nutrition goals when used in moderation. When eaten in excess, sugar alcohols can cause gas, bloating, and diarrhea. And higher blood levels of erythritol have been associated with a greater heart attack and stroke risk.