Simple vs complex carbohydrate

Simple versus complex carbohydrate effects how these food substances are absorbed and digested and, furthermore, understanding the distinction properly means you are far less likely to become obese and diabetic.

As a rule of thumb the former are more rapidly absorbed causing a surge in blood glucose and insulin, but there are strange exceptions to the rule. It all has to do with the fibre content.

For example, raw honey has a moderate GI, but white rice, commercial bread, and potatoes are very high.

Even sugar has a lower GI than white rice.

But brown rice, artisan sourdough bread and new potatoes are all quite different; it's a very difficult subject. Failing to grasp it is why there is a diabetic pandemic the world over; coupled with the virus makes it a killer.

Many complex carbohydrates, particularly those that have been refined, may also cause a blood sugar surge, but others pass through to the colon where they are fermented to form good short-chain fatty acids like butyrate, producing little insulin rush.

Some understanding of this difficult concepts of simple vs complex carbohydrate can transform your well-being.

This page was last updated by Dr Bernard Preston on 21st April, 2021.

Simple carbohydrates

There are two types of simple carbohydrates; those that are made up of single sugar molecules, known as monosaccharides.

And others where two glucose molecules, for example, combine to form disaccharides.

There are many monosaccharides, single sugars, and some you will be familiar with.

  • Glucose is a mono found for example in honey.
  • Fructose is another making fruit sweet.
  • Galactose is a monosaccharide found in sugar beets, avocados and many other foods.

These single sugar molecules are the simplest form of starch. How quickly they are absorbed from our food into the blood stream is measured by the glycemic index.

The GI of glucose is defined as 100, meaning it's very rapidly absorbed.

On the other hand, fructose, or fruit sugar, has a low GI of only 19.

However, don't think that therefore high-fructose corn syrup is not so bad; it is dreadful.

So too, the galactose in avocados is very slowly absorbed because of the fat and protein in the fruit; they have a GI of only 15.

So, simple carbohydrates are not bad, they are a ready source of energy but understanding them is vital.

It's a not uncommon misconception that all simple carbohydrates should be avoided, because they are rapidly absorbed, giving a blood glucose rush; but all complex starches are slowly digested and are good. It is completely false.

Cake flour for example, a complex carbohydrate, has a high GI of 70; white rice is even higher at 75. Much depends on how refined the food is; how much of the fibre has been removed.

Are you beginning to get a grasp of simple vs complex carbohydrate and how they can dramatically affect your well-being, for better or for worse?

Creamed vs runny honey.

Honey is a mixture largely of glucose and fructose; it has a moderate GI of about 50 depending on how refined it is, the amount of pollen and the ratio of fructose to glucose; it varies considerably from one flower to another.

The greater the fructose fraction, the lower the glycemic index.

There are many disaccharides too; where two sugars combine together and again some will be familiar.

  • Maltose, the sugar in beer, for example, is made up of two units of glucose. (GI 105)

          Glucose + glucose = maltose

  • Common table sugar, known as sucrose consists of a glucose and a fructose molecule that have combined. (GI 65)

          Glucose + fructose = sucrose

  • Lactose, the double sugar found in milk. (GI 45)

          Glucose + galactose = lactose

Generally, the more refined the carbohydrate, as the fibre, protein and fatty acids are removed, the GI rises. And maltose is top of the pops; that's why beer is so fattening.

So, it's time to move on in our discussion of simple vs complex carbohydrate to the latter sort.

Complex carbohydrates

Complex carbohydrates have long chains of sugar molecules. A starch consists of two types,

  • Amylose which has a helical structure that is more difficult for the enzymes to act on. An example would be pectin, the fibre found in many fruits which is resistant to digestion in the small intestine.
  • Amylopectin which has many branches and is rapidly digested. An example would be the potato which has a high GI.

Cooking and cooling has a dramatic effect on the GI of a starch.

For example, if you cook enough oats porridge for several days, taken hot at the first breakfast it will have a high glycemic index, but cooled in the refrigerator and then enjoyed tomorrow, the starch goes through a process called retrogradation, lowering the GI. Even reheating will have little effect.

Refined oats however should be avoided at all costs; once the fibre has been removed it becomes a very high GI food. Does yours come in a box, and are the flakes small? It is definitely not one of the good brain foods.

So, the subject is complex; how you prepare a carbohydrate, how much of the fibre is refined out, the amount of fat and protein present all affect whether it has a good influence on your body, or makes you obese and likely to become insulin resistant and eventually diabetic.

Complex carbohydrate which passes through the small intestine undigested, producing no blood glucose reaction, but reaching the colon is known as resistant starch.

In the colon it is fermented rather by the microbiota, a teaming myriad of friendly bacteria and yeasts, forming instead profoundly important short-chain fatty acids. In other jargon, it's known as a prebiotic; food for the bugs.

These bugs can easily become depleted, especially after taking antibiotics, many of which are found in small quantities in our foods; taking a probiotic like kefir helps to replenish this normal flora that is so important for our well-being.


A prebiotic is the fraction of the fibre in fruits, vegetables and grains that pass through the small intestine, reaching the colon where they are fermented instead by the microbiota[3]. Get them from whole foods like apples and broccoli, not from expensive supplements.


A probiotic is the living yeasts and bacteria, known as the microbiota, essential friendly bugs that are found in the intestine, and other organs like the bladder too. Take them in supplements if you must but, better still and way cheaper, find them in kefir benefits. It takes just a few minutes every morning to prepare your own.

Kefir in a funnel.

Simple vs complex carbohydrate

Simple vs complex carbohydrate is an important distinction to grasp.

Do not get caught in the trap, thinking that simple carbohydrate is all bad and must be avoided, but the complex variety is nutritious and can be enjoyed ad lib.

Milk and honey do contain simple sugars which, depending on how refined they are, producing a small glycemic reaction.

White bread and rice, and a host of crackers, cookies and buns are made with complex carbohydrate but have a very high glycemic effect; they make us fat. It really is a difficult subject.


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In short look for unrefined foods, whether starches or not; the amount of fibre has a dramatic effect on how quickly the sugars are absorbed into the blood stream.

This 100% wholemeal bread with added protein and good fat is an example of a low glycemic complex carbohydrate.

That protein comes from the excess curds produced by our homemade kefir and hummus that we process every week; the added fat from olive oil and coconut butter, and I'm going to be experimenting with avocado in the dough to see if it further lowers the GI.

100% wholemeal flour is almost impossible to purchase, because it goes rancid. Our solution is a wheat grinder; they are expensive but then the flour costs only R4 per kilogram (13ยข per pound).

If you bake your own bread then it's certainly cost effective.

kefir sourdough bread.

Taking a walk immediately after a starchy meal also has a dramatic influence on reducing the glucose rush. Have a candy bar or cola and sit at a computer or in front of the TV regularly and you are looking for trouble.

Finally, this difficult subject of simple vs complex carbohydrate is all about how the starch is prepared, refined, and the context of the whole meal.

Some useful links

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  1. Why does honey crystallise - all about the ratio of fructose to glucose.
  2. Kefir sourdough bread - bake it yourself.
  3. Microbial Degradation of Whole-Grain Complex Carbohydrates and Impact on Short-Chain Fatty Acids

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