The Worst Carb For Blood Sugar You’ve Probably Never Heard Of

[Update, November 17, 2025: This article was updated to include several powerful graphics from a 2025 paper about the health implications of maltodextrin as an additive in processed foods]

Introduction

A recently updated article titled Complex Carbohydrates as Long Chains of Sugar Molecules, explained that “complex carbohydrates” are really just long chains of sugar molecules, like pearls on a string, and that how quickly blood sugar rises depends on the specific types of sugars in those chains. 

Monosaccharides (made up of a single sugar molecule) are sugars such as glucose and fructose that break down very quickly and quickly impact blood glucose. 

Disaccharides (made up of two sugar molecules), such as sucrose (table sugar), are made up of glucose and fructose combined, and break down more slowly than monosaccharides like glucose and fructose. As a result, the rise in blood glucose is slightly slower than glucose. 

What if you found out that the worst carbohydrate for blood sugar is one that you’ve probably never heard of?

What if you found out that this carbohydrate is often found in sugar-free foods, but is not considered a sugar under Canadian food labeling regulations? 

That is what this article is about.

Glycemic Index (GI)

The Glycemic Index (GI) is a ranking system for carbohydrate-containing foods based on how quickly they raise blood sugar (blood glucose) levels after they are eaten.

Foods are ranked on a scale of 0 to 100, with pure glucose assigned a value of 100. 

High GI foods (ranked with a GI of 70 or more) are rapidly digested and absorbed, causing a quick and high spike in blood sugar levels.

Medium GI foods (ranked with a GI of 56-69) have a moderate effect on blood sugar levels.

Low GI foods (ranked with a GI of 55 or less) are digested and absorbed slowly, releasing glucose gradually into the bloodstream and causing a slower, smaller rise in blood sugar. 

As mentioned in the previous article, factors such as the amount of fiber in the food, as well as the amount of food processing of that food, including cooking, can affect a food’s GI value. 

The Glycemic Index of pure glucose (also called dextrose) is 100, the highest score.

The Glycemic Index of table sugar (i.e., sucrose) is rated with a GI of 65-80 (depending on the source) [4]. Sucrose is a disaccharide made of a mixture of glucose (which has a GI of 100) and fructose (which has a GI of 25). While its overall impact on blood glucose is significant, it is less than pure glucose, which is a monosaccharide, because sucrose takes longer to digest, and thus to spike blood sugar. 

The carbohydrate that you’ve probably never heard of has a Glycemic Index between 85 and 105 (depending on the source), which is higher than table sugar (sucrose) and higher than pure glucose. 

This carbohydrate is maltodextrin. 

Maltodextrin plays a functional role in food manufacturing, primarily serving as a bulking agent, thickening agent, and stabilizer. Products known to contain some of the highest maltodextrin content include sports and energy drinks.

Maltodextrin is also often found in sugar-free foods, but it is not considered a sugar under Canadian food labeling regulations; rather is classified as a “complex carbohydrate”, a polysaccharide food additive.

Note: The reliability of the Glycemic Index in predicting blood sugar responses in individuals was called into question in research conducted in 2016 and 2019, as outlined in this earlier article. However, it is still used, and for comparative purposes, it is used in this article.

What Is Maltodextrin and What Does It Do to Blood Sugar?

Maltodextrin is a refined carbohydrate made from starch — usually from corn, rice, potato, or wheat. Food manufacturers use it as a thickener, filler,  or stabilizer in a wide range of foods and drinks.

Although maltodextrin doesn’t taste very sweet, the body digests it similarly to pure glucose, so it can raise blood sugar very quickly.

Maltodextrin is created when starch is treated with enzymes to break it down into shorter chains of glucose molecules. Because it’s already partially digested, the body absorbs it quickly, giving it a Glycemic Index (GI) between 85 and 105 (depending on the source), which is significantly higher than regular table sugar (sucrose), which has a GI ≈ of 65 and can even be higher than pure glucose (dextrose). 

While maltodextrin has practical applications in the manufacturing of sports drinks or medical nutrition products where quick energy is needed, it is also found in a wide range of foods, including infant formula, protein supplements, and even sugar-free foods. 

Its presence in sugar-free foods is concerning because it can result in a very significant spike in blood sugar in those who are deliberately trying to avoid sugar.

Sucralose, used in the sugar-free sweetener Splenda®. It is made from sucrose (table sugar), where three hydroxyl groups (-OH) are replaced by chlorine. It is approximately 600 times as sweet as table sugar, so most of a packet of Splenda® is maltodextrin, used as a filler.  A 2008 research study found Splenda® to be 1.1% sucralose, 1.1 % glucose, 4.23% moisture, and >93.59% maltodextrin.

While Splenda® is “sugar-free”, the maltodextrin in it can cause blood glucose to spike significantly higher than table sugar. 

Below is a graph comparing the glucose spike from maltodextrin, glucose, and sucrose (table sugar). Table sugar (sucrose) spiked blood glucose to ~145 mg/dl (8.0 mmol/L) at 30 minutes, and maltodextrin spiked blood glucose to ~165 mg/dl (9.0 mmol/l) at 40 minutes.

Below is a bar chart illustrating the percentage of products containing maltodextrin.

Some of the highest maltodextrins are found in sports and energy drinks (84%); however, protein supplements have the same percentage of maltodextrin (84%), and infant formula has an even higher percentage (89%).

Maltodextrin is also present in a wide range of foods that are marketed as “healthy options”, including protein powders and meal replacement bars. As is the case with sugar-free foods containing maltodextrin, consumers rely on labels on these products to make informed dietary choices, unaware of the impact that maltodextrin can have on their blood sugar.

Why Blood Sugar Spikes Matter

Since maltodextrin digests and absorbs rapidly, it can cause rapid spikes in blood glucose and insulin levels.

Over time, repeated spikes can lead to:

• • Energy crashes or fatigue after meals

  • Increased hunger and sugar cravings

  • Blood sugar instability in people with diabetes, PCOS, or insulin resistance

  • Possible gut microbiome disruption when consumed in large amounts 

Final Thoughts…

Maltodextrin is a common hidden carbohydrate used in processed foods.

While maltodextrin may serve a useful role in the manufacturing of specialized products for athletes or in medical nutrition products, people relying on a  “healthy” protein shake or a meal replacement bar are usually unaware of the effect it can have on their blood sugar.  How much more do those with prediabetes or diabetes (type 1 or type 2) need to know which products, including sugar-free products, contain maltodextrin?

For those needing to control their blood sugar, it is recommended to read labels closely and limit foods containing maltodextrin. Choosing whole-food carbohydrate sources in amounts that can be monitored (“carb counting”) makes controlling blood sugar possible.

To your good health. 

Joy 

 

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References

1. 1. Brand‑Miller JC, Foster‑Powell K, Atkinson F. The International Tables of Glycemic Index and Glycemic Load Values. Am J Clin Nutr. 2002;76(1):5–56. 2008: DOI 10.2337/dc08-1239) [https://pubmed.ncbi.nlm.nih.gov/18835944/]
   2. U.S. Department of Agriculture (USDA). FoodData Central: Maltodextrin – Ingredient Profile and Energy Content. Washington, DC: USDA; Accessed 2024. URL: https://fdc.nal.usda.gov
   3. U.S. Food and Drug Administration (FDA). Code of Federal Regulations Title 21 – Maltodextrin (21 CFR 184.1444). Silver Spring, MD: FDA. URL: https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-184#p-184.1444
   4. Health Canada. List of Permitted Food Additives with Other Accepted Uses. Ottawa, ON: Health Canada; Updated 2023. URL: https://www.canada.ca/en/health-canada/services/food-nutrition/food-additives/permitted-use-additives.html
   5. Hofman, D. L., van Buul, V. J., & Brouns, F. J. P. H. (2015). Nutrition, Health, and Regulatory Aspects of Digestible Maltodextrins. Critical Reviews in Food Science and Nutrition, 56(12), 2091–2100. https://doi.org/10.1080/10408398.2014.940415
   6. Yarley EJ, Unveiling Hidden Sugars: A Critical Analysis of Maltodextrin as a Polysaccharide Additive in Processed Foods and Its Health Implications, International Journal of Medical Science and Clinical Invention 12(04): 7602-7621, 2025DOI:10.18535/ijmsci/v12i.04.02 https://valleyinternational.net/index.php/ijmsci
   7. Magnuson BA, Roberts A, Nestmann ER, Critical review of the current literature on the safety of sucralose, Food and Chemical Toxicology,
      Volume 106, Part A, 2017, Pages 324-355, https://doi.org/10.1016/j.fct.2017.05.047.
   8. Abou-Donia MB, El-Masry EM, Abdel-Rahman AA, McLendon RE, Schiffman SS. Splenda alters gut microflora and increases intestinal p-glycoprotein and cytochrome p-450 in male rats. J Toxicol Environ Health A. 2008;71(21):1415-29. [http://www.ncbi.nlm.nih.gov/pubmed/18800291]

 

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