The Correct Way to Calculate Net Carbs
Contrary to a common misunderstanding, added sugars are not subtracted from total carbohydrates to determine net carbs. Added sugars are digested and raise blood sugar levels.
To calculate net carbs accurately, subtract only dietary fiber and, in certain cases, sugar alcohols from the total carbohydrates. The basic formula is:
Net Carbs = Total Carbohydrates - Dietary Fiber - (some) Sugar Alcohols
This calculation is based on fiber's indigestibility and the reduced impact of some sugar alcohols on blood sugar.
Decoding the Nutrition Facts Label
Understanding a nutrition label is crucial for tracking carbohydrate intake. Key parts include:
- Total Carbohydrate: This covers all carbohydrates, including starches, sugars, and fiber.
- Dietary Fiber: Found under Total Carbohydrate, this is subtracted.
- Total Sugars: Includes natural and added sugars. Do not subtract.
- Added Sugars: The amount of sugar added during processing. It is part of Total Carbohydrate and is not subtracted.
- Sugar Alcohols: If listed, a partial amount may be subtracted.
The Logic Behind Not Subtracting Added Sugars
Added sugars are not subtracted because they are quickly absorbed, causing blood glucose levels to rise. Fiber, however, slows digestion and helps stabilize blood sugar. This metabolic difference explains the net carb calculation.
The Varying Impact of Fiber and Sugar Alcohols
Both fiber and sugar alcohols are often subtracted, but their effects differ.
Fiber
- Indigestible: Fiber supports digestive health without significantly raising blood sugar. It's typically fully subtracted.
Sugar Alcohols
- Partial Digestion: Most are partially digested, with a lower blood sugar impact than sugar.
- Variable Subtraction: Subtracting half the grams is common.
- Erythritol: This type is not digested and can be fully subtracted.
- Potential Side Effects: High intake can cause digestive discomfort.
Total Carbs vs. Net Carbs: A Comparison
Here is a comparison:
| Feature | Total Carbs | Net Carbs |
|---|---|---|
| Included Components | Starches, fiber, sugars, sugar alcohols | Digestible carbohydrates (Starches, sugars) |
| Calculation Method | Listed directly on the label | Manual calculation: Total Carbs - Fiber - (some) Sugar Alcohols |
| Health Authorities | Officially recognized by the FDA and ADA | Not officially regulated or defined |
| Blood Sugar Impact | All components (except fiber) have potential impact | Focuses only on carbs that impact blood sugar |
| Use Case | Recommended for accurate insulin dosing and general tracking | Popular for low-carb diets to track digestible carbs |
The Net Carbs Controversy and What It Means for You
The lack of regulation means companies may use net carb calculations for marketing. Calculating it yourself is recommended. Individuals with blood sugar concerns should monitor their levels, as responses vary.
Understanding nutrition labels and calculating net carbs correctly aids informed choices. Subtract only non-digestible parts like fiber and specific sugar alcohols, keeping added sugars in your count.
Conclusion
Do not subtract added sugars for net carbs; they are fully metabolized and part of total carbs. Calculate net carbs by subtracting dietary fiber and appropriate sugar alcohols. While useful for low-carb diets, the term is unregulated, and individual responses vary, making monitoring important. Prioritizing whole, fiber-rich foods is generally advised.
Sources
- American Diabetes Association: Get to Know Carbs
- Medical News Today: How to calculate net carbs, and what they mean
