What Exactly Are Polyols?
Polyols, often called sugar alcohols, are a type of carbohydrate used as low-calorie sweeteners in a wide array of foods and beverages, from sugar-free gum and candy to baked goods and protein bars. The name 'sugar alcohol' is a bit misleading as they are neither sugar nor alcohol in the conventional sense. They occur naturally in some fruits and vegetables, and can also be produced commercially. The primary appeal of polyols is their lower caloric content compared to sugar, ranging from nearly zero calories per gram for erythritol to approximately 2.4 calories per gram for others.
How the Body Processes Polyols
Unlike regular sugars and starches, polyols are only partially absorbed and metabolized by the body. This incomplete absorption is the key reason for their lower caloric value and minimal impact on blood glucose levels. While the human body possesses enzymes to digest most carbohydrates, these digestive systems are less effective at breaking down the complex structure of polyols. As a result, much of the polyol content travels undigested to the large intestine, where it is fermented by gut bacteria. This process is what can lead to the well-known digestive side effects, such as gas, bloating, and diarrhea, particularly when consumed in large quantities.
The Difference Between Total Carbs and Net Carbs
For those on low-carb or ketogenic diets, the concept of "net carbs" is more relevant than total carbohydrates. While the term isn't legally defined by the FDA in the US, it's widely used to represent the carbohydrates that actually impact blood sugar levels. The calculation typically involves subtracting dietary fiber and polyols from the total carbohydrate count listed on a nutrition label.
There is a crucial distinction in how this calculation is performed, depending on the polyol. Not all polyols are created equal in their effect on blood sugar. For instance, erythritol has a glycemic index (GI) of zero and is almost completely eliminated from the body unchanged, meaning its full amount can generally be subtracted from the total carb count. In contrast, polyols like maltitol have a much higher GI and can still cause a significant blood sugar response, so a full subtraction is not appropriate.
The Net Carb Calculation
To calculate net carbs, follow these steps:
- Find the 'Total Carbohydrate' amount on the nutrition label.
- Locate and subtract the 'Dietary Fiber'.
- Check for 'Sugar Alcohols' (polyols) listed under carbohydrates.
- Subtract the polyol amount, but adjust for the specific type:
- For erythritol, subtract the full amount.
- For most other polyols (maltitol, sorbitol, xylitol), subtract half the amount, as they have a partial impact on blood sugar.
Here’s an example:
- Total Carbs: 30g
- Dietary Fiber: 5g
- Sugar Alcohols (Maltitol): 10g
- Calculation: 30g - 5g - (10g / 2) = 20g Net Carbs
Comparison of Common Polyols
To highlight the differences, here is a comparison of some of the most widely used polyols:
| Feature | Erythritol | Maltitol | Xylitol | Sorbitol |
|---|---|---|---|---|
| Partial Absorption | Very low (nearly zero) | Moderate | Moderate | Moderate |
| Glycemic Index (GI) | 0 | ~50 | ~13 | ~9 |
| Calories per Gram | ~0.2 | ~2.1 | ~2.4 | ~2.6 |
| Digestive Effects | Low risk, less likely to cause issues | Moderate to high risk | Moderate to high risk | Moderate to high risk |
| Keto-Friendliness | Yes (subtract full amount) | Questionable (subtract half) | Good (subtract half) | Fair (subtract half) |
Potential Health Implications and Considerations
While polyols offer benefits like lower calories and blood sugar impact, and they do not cause tooth decay, there are important considerations. The digestive issues caused by incomplete absorption are a significant concern, especially for those with irritable bowel syndrome (IBS) or sensitive guts. Tolerance is highly individual, and consuming too much, too quickly can lead to discomfort. For this reason, food items containing more than 10% added polyols often carry a warning about laxative effects.
Another point of caution comes from the American Diabetes Association, which notes that "net carbs" isn't a regulated term and the actual impact on blood glucose can vary based on the specific fiber and polyol types present. Therefore, monitoring your own blood glucose response to polyol-containing foods is the most accurate method for managing diabetes or a keto diet. The FDA does, however, not require polyols to be labeled as 'added sugars', further distinguishing them from regular sugar on nutritional labels.
Conclusion
To definitively answer the question "do polyols count towards carbs?", the answer is yes, they are carbohydrates, but they do not count in the same way as regular sugar or starches. Their impact is significantly lower, and this is why they are often subtracted when calculating 'net carbs' for specific dietary plans like keto. The key takeaway is to recognize that different polyols have different effects on the body and that individual tolerance varies. By understanding how to properly calculate net carbs based on the specific polyol, and by monitoring your body's personal response, you can effectively incorporate these sugar alternatives into your diet without derailing your health goals. For more in-depth information on the metabolic pathways of polyols, the National Center for Biotechnology Information (NCBI) offers comprehensive resources, such as this article on the Polyol Or Sorbitol Pathways.
