Slow Carbs vs Fast Carbs
What Makes Some Carbohydrates Better Than Others?

What makes slow carbs better for your blood sugar than other carbs?

Although carbohydrates are the main fuel for our body, they don't all burn at the same speed. For example, white rice has a higher Glycemic Load (GL) than honey, meaning that it burns much faster and gives a quicker rise in blood sugar than honey. How is that possible?

To understand how this works let's consider the composition of carbohydrates.

Both slow carbs and fast carbs consist of starches and sugars. Starch is made up of sugar molecule bound together in long chains. When you eat a carbohydrate-rich food, your body converts those starches and sugars into glucose, or blood sugar.

Some starches, such as those in white rice, are extremely easy for the body to convert and therefore blood sugar levels rise quickly after you eat them. Other, like those in beans, are slow carbs and take a lot more work to break down, so blood sugar levels simmer rather than explode.

Four factors determine how fast the body breaks down carbohydrate:

The Type of Starch

As we've seen, starches are made of sugar molecules chained together. Some chains are straight, while others are branched. The straight-edged type, called amylose, is harder for your body to break down and turn into sugar, making the carbohydrates slow carbs.

The branched type, called amylopectin, is much easier to break down because there are so many places for the enzymes to get it and they're the so called fast carbs.

White potatoes too are very high in amylopectin, the branched kind of sugar chain, which is why they raise your blood sugar in the blink of an eye.

Peas and lentils are high in amylose, the straight-edged type, so they're converted into blood sugar at a snail's pace and they're good slow carbs.

Basically, the more amylose a food contains, the slower it will be converted into blood sugar.

Let's go back to rice. Some types of rice contain more amylose than others.

In general, the softer and stickier the rice is after cooking, the lower its amylose content and therefore the higher is its GL value.

The firmer the rice, the higher the amylose content it is and the harder it is for your body to turn it into blood sugar quickly - making brown rice a much better choice.

The Type of Sugar

Sugar is the molecule that makes up carbohydrates, but there is more than one type of sugar.

There's table sugar (sucrose) as well as the kind found in fruits and grains (fructose), the kind in milk (lactose) and the kind in malted barley (maltose).

The sugar in milk and fruit tends to be absorbed more slowly than other sugars because it needs to be converted into glucose by the liver first, which is why these foods don't cause a sudden rise in your blood sugar.

Ironically, table sugar, which is half fructose and half glucose, is turned into sugar more slowly than some starches, like bread or potatoes.

That doesn't make sugar good for you, though. One reason is that fructose, especially in the amounts contained in packaged foods loaded with high-fructose corn syrup, raises triglycerides, blood fats that increase the risk of heart attack.

Fruit, by contrast, contains a little fructose plus plenty of water, fiber and nutrients and this is why it's much better for you.

Table sugar also packs a lot of carbohydrate calories in a small amount. A large cola, for example, contains 55 g. of sugar and 225 kcal - and it will send your blood sugar sky high.

All forms of concentrated sugar - white sugar, brown sugar, malt, glucose, honey and syrup - are fast releasing, causing a rapid increase in blood sugar levels. If sugar is not required by the body it's put into storage as fat.


All starch, whether it's made of straight or branched chains, is composed of crystals, which don't dissolve in cold water.

Think of a grain of rice or a piece of raw potato - put it in water and it stays the same. But heat breaks down those crystals so that starch can dissolve in water.

When you cook a starchy food, it absorbs water and becomes easier to digest. The process of refining or even cooking a food starts to break down complex carbohydrates into simple carbohydrates called maltose, in effect predigesting them.

The more overcooked rice or pasta is, the faster it makes your blood sugar rise. When starch is heated and then cooled, it can return, in part, to its crystal form; that's why hot potatoes have a high GL, while the GL of cold potato salad is slightly lower.


Have you noticed that some brown breads are as smooth as white bread, while others have crunchy kernels in them? Those kernels take a long time for your body to break down, as do any whole, intact grains.

Modern commercial flour, on the other hand, especially white flour, having been finely ground, is extremely easy for the body to turn into blood sugar.

This is why you should choose slow carbs such as whole grains that are still intact or have had very little processing and foods such as beans and lentils instead of those made from white flour.

As we're surrounded by white flour foods, you'll need to make a conscious effort to cut back.

It's not just white flour that you need to guard against, but look out for other processed foods as well.

Modern manufacturing allows grains to be turned into highly processed forms such as cornflakes or puffed corn snacks, which tend to have higher GIs than grains left intact, like popcorn, or those milled in an old-fashioned manner, such as coarse, stone-ground wholemeal flour used in stone-ground bread.

Slow Carbs vs Fast Carbs in Bread and Pasta

Let's make a comparison between bread and pasta. Even if they were made with the same flour and using the same amount, which one do you reckon would raise your blood sugar quicker?

Did you say bread? You'd be right. Bread, even some wholemeal breads, can raise blood sugar pretty quickly. Yet pasta, even if it's made from white flour, has a much lower GI. But why?

First of all, imagine putting cooked pasta and a piece of bread in a bowl of water. The bread will fall apart but the pasta won't. That's because in pasta dough, the starch granules get trapped in a network of protein molecules, so it takes more work - and more time - to get at them.

Similarly, gnocchi, a pasta-like product made with durum wheat and potato flour, have a lower GL than potatoes.

Bread is risen by feeding sugar to yeast, which makes bubbles, hence producing a lighter loaf. Then it's cooked for considerable time (compared to pasta).

Some types of pasta are essentially made with wheat and some egg, increasing the protein content and lowering the carbohydrate content. Also it isn't cooked for long - if eaten "al dente" (that is, slightly undercooked or with a firm texture) has an even lower GI.

That's why pasta releases its carbs much more slowly than potatoes or most breads. So a small difference in preparation makes a big difference in blood sugar response. For this reason, bread will make you put on weight much more than pasta, even if you eat the same calories!

The best type of pasta is whole grain pasta, as it contains fiber that slows down digestion, releasing glucose gradually.

Having considered the difference between slow carbs and fast carbs, you may now want to go back to the Whole Grain Foods main page or just click on Next.



Benefits of Fiber and High-fiber foods in your Diet

The Best Fiber Supplement

Soluble and Insoluble Fiber

High Fiber Diet Plan


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Articles in The Whole Grains Series

Whole grain Foods (Main Page)

Benefits of Whole Grains

What Are "Whole Grains?"

Whole Grain Cereals

Slow Carbs vs Fast Carbs - What Makes Some Carbs Better than Others?

Glycemic Index of Foods - What is It?

Glycemic Index and Glycemic Load -What is the Difference?

Low GI Foods

Low GI Food List