What Are Sugar Alcohols and Why Are They Used on Keto?
Sugar alcohols, or polyols, are a type of carbohydrate that has a chemical structure resembling both sugar and alcohol. Despite the name, they do not contain ethanol and are not alcoholic. The primary reason they are so popular in keto and low-carb products is that they are not fully digested by the body. This incomplete digestion means they have a lower calorie content and a less significant impact on blood sugar levels compared to table sugar.
For someone on a ketogenic diet, which requires a very low daily carbohydrate intake, sugar alcohols provide a way to enjoy sweetness without consuming excessive carbs that could disrupt ketosis. This state is where the body burns fat for fuel instead of glucose.
The Rise of "Net Carbs"
For keto followers, the concept of "net carbs" is key. Net carbs are the carbohydrates that are actually absorbed by the body and affect blood glucose levels. They are calculated by taking the total carbohydrates and subtracting dietary fiber and, in some cases, all or a portion of the sugar alcohols listed on the nutrition label. However, it's important to remember that not all sugar alcohols are created equal, and their digestion can vary significantly.
How to Subtract Sugar Alcohols to Get Net Carbs
Calculating net carbs requires careful label reading and an understanding of the different types of sugar alcohols. Here is a step-by-step approach to get the most accurate count:
- Find the Total Carbohydrates: Locate the "Total Carbohydrate" line on the food's nutrition label.
- Subtract Dietary Fiber: Look for the "Dietary Fiber" line and subtract that amount from the total carbohydrates. Fiber is indigestible and does not affect blood sugar.
- Identify and Adjust for Sugar Alcohols: Find the "Sugar Alcohol" line. This is where it gets tricky, as the amount you subtract depends on the type.
- Full Subtraction (1:1 Ratio): For some sugar alcohols, like erythritol, which is poorly absorbed and has a glycemic index of 0, you can subtract the full amount from your total carbs.
- Partial Subtraction (2:1 Ratio): For other sugar alcohols, such as maltitol and sorbitol, which are partially absorbed, it is often recommended to subtract only half the grams. This is a safer approach to ensure you don't underestimate your carb intake.
- Consider Other Sweeteners: Some products use other low-carb sweeteners like monk fruit or stevia, which are not sugar alcohols and typically have no caloric or glycemic impact. These are generally safe for keto and do not require subtraction.
A Closer Look at Common Sugar Alcohols
Erythritol: A Keto Favorite
Erythritol is widely considered the best sugar alcohol for the keto diet. It has a near-zero glycemic index and is poorly absorbed by the small intestine, with most of it passing through the body unchanged. This leads to minimal impact on blood sugar and fewer digestive issues compared to other sugar alcohols, although excessive amounts can still cause some discomfort.
Maltitol: The Tricky Sweetener
Often found in sugar-free chocolates and candies, maltitol has a higher glycemic index (up to 52) than other keto-friendly sugar alcohols. This means it can raise blood sugar more significantly. For many keto dieters, subtracting only half of the maltitol content is the recommended approach to avoid an unexpected carb spike that could knock them out of ketosis.
Xylitol: Great for Teeth, Not for Dogs
Xylitol is as sweet as sugar but with 40% fewer calories. It is known for its dental benefits, as it doesn't promote tooth decay. However, it is also partially absorbed, so counting half of the carbs is a safe bet for keto. Crucially, xylitol is highly toxic and potentially lethal to dogs, so extreme caution is required around pets.
Sorbitol: A Weaker Impact
Sorbitol is another sugar alcohol that is only partially absorbed, with a moderate effect on blood sugar. It is often used in a variety of sugar-free foods and can cause digestive distress if consumed in large quantities. Like maltitol, subtracting only half of the carb content is a good strategy on keto.
Comparison of Common Sugar Alcohols
| Sugar Alcohol | Glycemic Index (GI) | Carb Counting Approach (Keto) | Digestive Impact (in excess) |
|---|---|---|---|
| Erythritol | 0 | Subtract 100% | Minimal |
| Maltitol | 35-52 | Subtract 50% | Moderate |
| Xylitol | 7-13 | Subtract 50% | Moderate |
| Sorbitol | 9 | Subtract 50% | Moderate |
| Mannitol | 0 | Subtract 100% | Moderate |
How to Avoid Common Pitfalls with Sugar Alcohols
To successfully incorporate sugar alcohols into your keto diet, mindful consumption is key. Overindulging in seemingly "free" sweet treats can lead to consuming more carbs than intended, jeopardizing your ketosis. A phenomenon known as the “Snack Well effect,” where dieters overeat a food because they perceive it as healthy, is a real risk. Focus on whole, unprocessed foods naturally low in carbs and use keto-friendly alternatives in moderation.
Additionally, be aware of the digestive effects. Large doses of sugar alcohols can cause bloating, gas, and diarrhea, as they ferment in the colon. Starting with small amounts and monitoring your body's reaction can help you find your tolerance level.
Conclusion
Navigating whether to subtract sugar alcohol from total carbs on keto depends on the specific sweetener you are consuming. The rule is not a one-size-fits-all approach. For those with a near-zero glycemic index, like erythritol, you can generally subtract the full amount. For others, particularly maltitol, taking a more conservative approach and subtracting only half is the safer option to stay within your daily carb limit. Ultimately, relying less on processed, sweetened products and more on whole foods is the best strategy for long-term ketogenic success and optimal health.
For more information on net carb counting and keto-friendly sweeteners, consult with reliable resources such as the UCSF Diabetes Teaching Center for guidance.
