What Are Sugar Alcohols and Net Carbs?
Sugar alcohols, also known as polyols, are a type of carbohydrate commonly used as sweeteners and bulking agents in 'sugar-free' or 'low-carb' products. While they provide a sweet taste, their chemical structure differs slightly from regular sugar, preventing them from being fully absorbed by the body. This incomplete absorption is the basis for the concept of 'net carbs.'
Net carbs are the carbohydrates that are fully digested by the body and impact your blood sugar levels. They are calculated by taking the total carbohydrates and subtracting dietary fiber and the appropriate amount of sugar alcohols. It is important to note that the term 'net carbs' is a marketing term and is not legally defined or regulated by the Food and Drug Administration (FDA).
How to Subtract Sugar Alcohol from Carbs
Calculating net carbs requires a nuanced approach because not all sugar alcohols are the same. Their rate of digestion and effect on blood sugar vary significantly.
The General Rule for Partial Subtraction
For most sugar alcohols, including maltitol, xylitol, and sorbitol, a common practice is to subtract only half of the listed grams from the total carbohydrates. This method accounts for the partial absorption of these compounds. For example, if a product contains 10 grams of sugar alcohols, you would subtract 5 grams from the total carbohydrate count.
The Erythritol Exception
Erythritol is a unique sugar alcohol because it is almost entirely unabsorbed by the body and has a negligible effect on blood glucose. As a result, when erythritol is the only sugar alcohol listed, you can subtract the full amount from the total carbohydrates when calculating net carbs.
The Role of Fiber
When calculating net carbs, you should also subtract the dietary fiber, which is indigestible. The full calculation is:
Total Carbohydrates - Dietary Fiber - Sugar Alcohols = Net Carbs
Remember to apply the specific subtraction rule for the type of sugar alcohol present.
Understanding Different Sugar Alcohols
Different sugar alcohols have different glycemic indexes and potential for causing digestive issues. This knowledge is critical for those managing conditions like diabetes or sensitive digestive systems.
| Sugar Alcohol | Glycemic Index (GI) | Calories per Gram | Subtraction Guideline |
|---|---|---|---|
| Erythritol | ~0 | ~0.2 | Subtract full amount |
| Xylitol | 7-13 | ~2.4 | Subtract half amount |
| Sorbitol | ~9 | ~2.6 | Subtract half amount |
| Maltitol | 35-52 | ~2.1 | Subtract half amount |
Considerations and Potential Downsides
While subtracting sugar alcohols can be a helpful strategy, it's not without potential downsides. Overconsumption can lead to unpleasant gastrointestinal side effects.
Potential for Gastrointestinal Discomfort
Because sugar alcohols are poorly absorbed in the small intestine, they can be fermented by gut bacteria in the large intestine, which can cause gas, bloating, stomach cramps, and a laxative effect. Some individuals are more sensitive than others, and the effects depend on the specific sugar alcohol and the amount consumed. Sorbitol and mannitol, in particular, are known for their laxative properties.
Varying Individual Responses
Your body's unique metabolism, gut microbiome, and dietary habits can influence how you respond to sugar alcohols. For this reason, relying solely on net carb calculations can be misleading. Monitoring your body's response, especially your blood glucose levels, is recommended.
The Unofficial Nature of 'Net Carbs'
As the FDA and ADA do not officially recognize 'net carbs', some manufacturers may use the term differently, sometimes inflating the health halo of their products. Always examine the ingredients list and pay attention to how your body responds to new products. To learn more about navigating low-carb sweeteners and their impact on your diet, consult this Low-Carb Eating Guide.
Who Should Pay Attention to Net Carbs?
Understanding how to calculate net carbs is most relevant for two primary groups:
- Keto and Low-Carb Dieters: For those following a ketogenic diet, managing carb intake is essential for staying in ketosis. Subtracting sugar alcohols and fiber can help accurately track their impact carbs and expand food options.
- People Managing Diabetes: Since some sugar alcohols have a minimal effect on blood sugar, they can be a suitable alternative to sugar. However, they are not a 'free' food, and carb counting should include a careful accounting of sugar alcohols to prevent blood sugar spikes, especially with non-erythritol types.
Conclusion
Yes, you can subtract sugar alcohol from carbs, but the method and accuracy depend on the type of sugar alcohol and your individual metabolism. It is a useful strategy for those on low-carb diets or managing diabetes to estimate a food's glycemic impact, but it should be approached with caution. Remember that 'net carbs' is not a universally defined term, and individual tolerance to sugar alcohols can vary. For the most accurate and safe approach, particularly for managing health conditions, monitor your body's response and consult with a healthcare provider or registered dietitian.
