How Does Sweetener Have Carbs But No Calories?

November 2, 2025 •

4 min read

Did you know that food manufacturers can legally label a product as "zero-calorie" if it contains fewer than 5 calories per serving? This legal provision, combined with the unique digestive properties of certain chemical compounds, explains how a sweetener can have carbs but no calories.

Quick Summary

The discrepancy between carbs and calories in some sweeteners is due to incomplete absorption of sugar alcohols, non-metabolized artificial compounds, and legal labeling loopholes. Most of the caloric content is either unused by the body or negligible per serving.

Key Points

Sugar Alcohols are Incompletely Absorbed: Polyols, or sugar alcohols, are carbohydrates that the body only partially absorbs, resulting in fewer calories than standard sugar.
FDA Labeling Permits Rounding: Regulations allow food products with less than 5 calories per serving to be rounded down and labeled as "zero-calorie".
Artificial Sweeteners Bypass Metabolism: Compounds like sucralose and saccharin are not metabolized for energy, meaning they provide sweetness without adding calories.
Bulking Agents Contribute Negligible Carbs: Packet sweeteners use fillers like dextrose or maltodextrin, which are carbohydrates, but in amounts small enough to be labeled as having zero carbs per serving.
Erythritol is Excreted, Not Metabolized: While technically a sugar alcohol and carbohydrate, erythritol is absorbed by the small intestine and then excreted in urine without being turned into energy, making its calorie count negligible.
Non-Digestible Fiber Reduces Calories: The principle of undigestible carbohydrates applies to fiber, which is counted as a carb on a nutritional label but does not contribute significant calories.

The Science of Sweeteners: How Carbs Become Calorie-Free

The perception that all carbohydrates contribute significant calories is a common misconception. The truth lies in the human body's inability to fully process certain carbohydrate structures for energy. This is the fundamental reason how a sweetener can have carbs but no calories. Different types of low-calorie and zero-calorie sweeteners achieve this in a few distinct ways, primarily through non-metabolized compounds and the partial absorption of sugar alcohols. Understanding this process requires a look into food chemistry and federal labeling laws.

Non-Metabolized Artificial Sweeteners

Some of the most popular zero-calorie sweeteners are artificial compounds that pass through the body essentially untouched, providing no energy whatsoever.

Sucralose: The active ingredient in Splenda, sucralose is made from sugar through a multi-step process that replaces three hydrogen-oxygen groups with chlorine atoms. The resulting molecule has a sweet taste but is not recognized by the enzymes in our digestive system. Approximately 85% of consumed sucralose is not absorbed, and the small amount that is absorbed is not broken down for energy. This is why sucralose is completely calorie-free.
Other artificial sweeteners: Compounds like saccharin and acesulfame potassium are also not metabolized by the human body for energy. Since they are hundreds of times sweeter than sugar, only tiny, un-caloric amounts are needed to achieve the desired sweetness.

The Role of Sugar Alcohols (Polyols)

Sugar alcohols, also known as polyols, are a category of carbohydrates with a unique chemical structure. Unlike regular sugar, which is quickly and completely absorbed, most sugar alcohols are only partially digested in the small intestine. The unabsorbed portion then travels to the large intestine, where it can be fermented by gut bacteria, but this process still results in far fewer calories than metabolizing sugar.

A list of common sugar alcohols includes:

Erythritol
Xylitol
Sorbitol
Maltitol
Isomalt

Erythritol is a notable outlier among sugar alcohols because it is more readily absorbed in the small intestine but is then excreted in the urine without being metabolized for energy. This makes its caloric contribution negligible (about 0.2 calories per gram) compared to other sugar alcohols that provide 1.6 to 3 calories per gram. This difference explains why some products with erythritol can claim zero calories.

How FDA Labeling Regulations Play a Part

The FDA's food labeling guidelines significantly influence how manufacturers present the nutritional information for low-calorie sweeteners. For single-serving packets, the rules permit a product to be labeled as having "zero calories" and "zero carbohydrates" if the amount is below a certain threshold.

The 5-Calorie Rule: Any food item with fewer than 5 calories per serving can be labeled as having 0 calories.
The 1-Gram Carb Rule: Similarly, products with less than 1 gram of carbohydrates per serving can be rounded down to 0 grams of carbs.

This is often the reason why individual packets of sweeteners, even those containing small amounts of carbohydrates from bulking agents like maltodextrin or dextrose, carry a "zero-calorie" claim. While the amount is nutritionally insignificant in a single packet, consuming multiple packets can add up over the course of a day.

The Importance of Incomplete Digestion

Beyond artificial compounds and sugar alcohols, there is a general principle in nutrition that applies to certain types of carbohydrates: if the human body cannot break them down, it cannot extract energy from them. Dietary fiber, for example, is a carbohydrate that is mostly indigestible by humans. The energy content of fiber is very low, as it passes through the digestive tract largely intact. This same mechanism—the body's lack of appropriate digestive enzymes—is what allows some sweeteners and fillers to provide sweetness and bulk without a significant caloric load.

Sweetener Comparison: How They Affect the Body


Feature	Regular Sugar	Artificial Sweeteners (e.g., Sucralose, Stevia)	Sugar Alcohols (e.g., Erythritol, Xylitol)
Carbohydrate Content	4g carbs/tsp	Zero carbs in the sweetener compound itself (packets may contain bulking agents)	Varies by type (e.g., 4g carbs/tsp for pure erythritol, ~0.2g net)
Calories per gram	~4 calories	Essentially 0 calories	Varies significantly (Erythritol: 0.2, Maltitol: 3)
Digestion/Absorption	Absorbed quickly and completely; metabolized for energy	Mostly unabsorbed or not metabolized for energy	Incompletely absorbed; fermented by gut bacteria
Impact on Blood Sugar	Significant increase	Minimal to no impact	Minimal impact; lower glycemic index
Possible Side Effects	Weight gain, dental decay	Ongoing debate, generally safe in moderation	Laxative effect and digestive issues in high doses

Conclusion: The Final Word on How Sweeteners Have Carbs but No Calories

The ability for a product to contain carbohydrates yet report zero calories is not a form of trickery, but rather a result of food science and regulated labeling conventions. It comes down to how the human body processes different types of sweeteners. Non-nutritive, artificial sweeteners like sucralose pass through the system without providing energy. Meanwhile, sugar alcohols are a type of carbohydrate that our bodies cannot fully absorb or metabolize, yielding far fewer calories than regular sugar, with some like erythritol being nearly zero-calorie due to rapid excretion. When combined with FDA rules that allow for rounding small calorie and carb amounts down to zero, this creates the unique nutritional profile found in many popular low-calorie and diet products. Consumers should be aware of these mechanisms to make informed choices about their dietary sweetener intake, especially regarding sugar alcohol consumption in large quantities and the potential for digestive side effects.

For more detailed information on sweeteners, the International Sweeteners Association offers resources outlining the different types and their properties.

Frequently Asked Questions

A single-serving packet of Splenda contains a minute amount of the non-caloric sweetener sucralose along with bulking agents like maltodextrin and dextrose, which are carbohydrates. The FDA allows rounding down to zero for both calories (if under 5) and carbs (if under 1g) per serving, so the small amount of carbs from the filler is legally negligible.

Artificial sweeteners like sucralose or aspartame are highly potent compounds that the body cannot metabolize for energy, so they are truly zero-calorie. Sugar alcohols like erythritol or xylitol are carbohydrates that are only partially absorbed, providing some calories but significantly fewer than regular sugar.

Yes, almost all sugar alcohols contain some calories, but significantly fewer than sugar because they are incompletely absorbed. Erythritol is a unique exception, with only about 0.2 calories per gram, as it is mostly excreted from the body unchanged.

If the carbohydrates listed come from sugar alcohols, the body absorbs them poorly, so they contribute very few calories. For labeling purposes, manufacturers may still need to list them under total carbohydrates, especially in larger serving sizes where the total amount is more substantial than a single packet.

Net carbs are calculated by subtracting fiber and sugar alcohols from the total carbohydrate count. The premise is that these carbs are not fully absorbed and therefore have a lesser impact on blood sugar. However, the FDA does not officially endorse this calculation, and absorption can vary.

Yes, excessive intake of most sugar alcohols can cause gastrointestinal distress, such as bloating, gas, and diarrhea, because they draw water into the large intestine due to their incomplete absorption. Erythritol is generally better tolerated than other sugar alcohols.

Sweeteners like erythritol are commonly used on keto diets because their low net carb count and minimal impact on blood sugar fit the dietary goals. However, those on a strict keto diet should be mindful of larger quantities of any sweetener, especially those containing bulking agents, to avoid unknowingly consuming extra carbs.