Simple vs complex carbohydrate

Simple vs complex carbohydrate effects how these food substances are absorbed and digested and, furthermore, understanding it properly means you are far less likely to become obese and diabetic. As a rule of thumb the former are rapidly absorbed causing a surge in blood glucose and insulin, but there are strange exceptions to the rule.

This page was last updated by Dr Bernard Preston on 27th June, 2019.

By Bernard Preston

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

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 healthy short chain fatty acids like butyrate, producing no insulin rush.

Some understanding of this difficult structure of simple vs complex carbohydrate can transform your health.

Simple carbohydrates

There are two types of simple carbohydrates; those that are found are made up of single sugar molecules, known as a monosaccharide, and those where two sugar molecules combine to form a disaccharide.

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 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.

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.

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

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 honey to another; the higher the fructose concentration, 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.

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.

So, the subject is complex; how you prepare a carbohydrate, how refined it is, the amount of fat and protein present all affect whether it has a healthy 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 healthy bacteria and yeasts, forming instead 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 health.

Prebiotic - 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. Get them from whole foods like apples and broccoli, not from expensive supplements.

Probiotic - living yeasts and bacteria, known as the microbiota, are essential healthy bugs found in the colon. Take them in supplements or better still find them in kefir benefits. It takes just a few minutes every morning to prepare your own.

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 healthy and can be enjoyed ad lib.

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

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

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

This 100% wholemeal bread with added protein and healthy 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 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 (13¢ per pound).

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

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

Why does honey crystallise - all about the ratio of fructose to glucose.
Kefir sourdough bread - bake it yourself.

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