Glucose and other carbs

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Dr. Dennis Van Hoof, PhD, CLC

“There are many different types of sugars”


Glucose and other carbs

Carbon Oxygen Hydrogen

Water (H2O) is made out of 2 hydrogen atoms and 1 oxygen atom. Carbon dioxide (CO2) consists of 1 carbon atom and 2 oxygen atoms.

The term “carbs” is short for carbohydrates, which is a general name for all kinds of sugars. The word carbohydrate consists of two words fused together: carbon and hydrogen (carbo-hydrate). Those are the building blocks (atoms) that make up sugars. There is actually a third atom also part of sugar, which is oxygen. The molecules water and carbon dioxide are made of the same atoms: water has 2 hydrogen atoms and 1 oxygen atom (H2O), and carbon dioxide has 1 carbon and 2 oxygen atoms (CO2).

Carbohydrates (sugars) come in two different forms: simple sugars and complex sugars.

Simple sugars — Glucose is probably the most famous simple sugar. Glucose is made out of 6 carbon, 12 hydrogen and 6 oxygen atoms (C6H12O6). 5 out of these 6 carbon atoms are connected to eachother, forming a ring with 1 oxygen atom closing the loop. The carbon and oxygen atoms have hydrogen atoms attached to them, as shown in the figure below.

Glucose molecule buildup

From left to right you can see the buildup of a glucose molecule. C = Carbon, O = Oxygen, H = Hydrogen. Glucose has a total of 6 carbon atoms, 6 oxygen atoms and 12 hydrogen atoms that are connected to form a circular structure.

Fructose molecule

Fructose (the hydrogen atoms are left out of the picture for clarity)

Fructose is another well-known sugar. Like glucose, fructose consists of 6 carbon, 6 oxygen and 12 hydrogen atoms. But its structure is a bit different from glucose. While glucose is a ring of 6, fructose is a ring of 5.

Plants can link glucose and fructose together to make sucrose. When they are linked, one oxygen atom forms the bridge, and bumps away the other oxygen atom in the form of water (see figure below). Although sucrose consists of 2 different sugar molecules, it is still considered a simple sugar.

Sucrose molecule

Sucrose is made out of glucose and fructose that are linked together.  (the hydrogen atoms are left out of the picture for clarity)

Sucrose is the most commonly used sugar in foods and drinks; it is the white crystal sugar that we use for instance for baking or to sweeten our coffee. All these simple sugars have a relatively high Glycemic Index (see Blog post “Glycemic Index and Glycemic Load“).

Complex sugars — Complex sugars are large molecules made out of many sugar molecules that are linked together (see Blog post “The bitter-sweet truth“). Starch is made by plants and consists of long chains of hundreds glucose molecules. Plants make this to store large amounts of sugar for later use.



When eating food that contains starch, it takes your body time and effort to break down the starch into single glucose molecules. That’s why starch has a lower Glycemic Index than sucrose or glucose (see Blog post “Glycemic Index and Glycemic Load“).

Animals (including humans) can also store large amounts of glucose for later use. Instead of starch, animals make glycogen, which consists of a protein (glycogenin) that has thousands of glucose molecules attached to it in a branched structure.



Glycogen is stored in your muscles as well as in your liver. Your muscles use that stored glycogen for energy to flex. Your liver releases the glucose from those glycogen molecules into your blood stream in response to the hormone glucagon when your blood glucose is running low (see Blog post “Insulin and diabetes“).

Other types of carbs — Fiber is a carb too, but it doesn’t change your blood glucose when you eat it. Humans do not have the right enzymes to break down those complex carbs into simple sugars. That’s why your body cannot use them for energy or store them for later use. You will not increase your blood glucose level or gain weight from eating fiber, but simply flush the fiber down the toilet after digestion.

If you want to learn more about a healthy and active lifestyle, without diets and restrictions or limitations, then follow me on social media like Facebook, LinkedIn and Instagram.

Also check out my website, and consider signing up for the personal diabetic lifestyle coaching or one of the online group workshops that I offer through video conference.

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Keep an eye out for my next blog, and I hope to see you soon to get you started on the journey to your new life!

—  Dennis


Dr. Dennis Van Hoof is a Certified Life Coach (CLC) with an academic PhD degree in Biochemical Physiology. By combining 20 years of first-hand personal diabetes experience with his in-depth scientific background, he developed a method to efficiently manage his own diabetes in a sustainable way. To learn how you can do this too, reach out for personal Diabetic Lifestyle Coaching or follow a group workshop that is specifically tailored to people with Type 1 or 2 Diabetes as well as pre-Diabetics and those at risk due to being overweight or obese. His clients thrive with their challenges and become an inspiration™ to others — with or without diabetes.

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