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Carbs 101
As you can imagine, we have been asked many questions about carbs over the 12 years we have been publishing GI News. In Food for Thought it’s back to basics as we share our answers to some common FAQs: what are carbs, where do they come from, why are the good ones important, and why the GI matters.

What are carbs?
The word “carbohydrate” comes from chemistry and means “watered carbon” (or carbon with water molecules). Sometimes you will see it shortened to CHO which stands for carbon, hydrogen and oxygen. Here’s what the chemical formula of glucose looks like: C6H12O6 (which stands for six carbon atoms and six water molecules – H2O = water).

Carbs are one of four major molecules in our foods, and like two of the others – protein and fat – they provide us with the energy (calories or kilojoules) to power our lives. Water, the fourth major molecule, has no calories. Most foods are a mix of these molecules. Take half a cup (about 95g/3oz) of cooked quinoa. It provides 400 kilojoules (96 calories), 4g protein, 2g fat, 15g carbs (1g sugars, 14g starches), 2g fibre, 4mg sodium, 150mg potassium, and has a low GI (53) and GL (8).

They come in a number of guises. Sugars are carbs, so are starches and the bonus indigestible dietary fibres and resistant starches that nourish the gut, feed the friendly bacteria and keep things moving along nicely on the inside.

Where do they come from?
Mostly plants. One way or another, green plants provide us with the energy that fuels our lives from the fossil fuels formed millions of years ago to the foods we grow. Carbohydrate energy comes from plant photosynthesis. To put it as simply as possible, the green cells (chlorophyll) in a plant’s leaves use sunlight’s energy to convert the carbon dioxide they absorb from the air and the water they draw up through their roots into the sugars and starches they need to grow and produce the roots, tubers, stems, leaves, flowers, fruits and seeds. They also use it to make their (indigestible to us) cell wall materials such as cellulose, hemicellulose and lignin, along with various gums and pectins. And there’s more, there’s the oxygen they release into the atmosphere so we can all breathe easy.


Why are they important?
Good carbs are multi-talented molecules that play key roles in our body. Our brains, nervous system, red blood cells, kidneys and muscles during exercise prefer carbs as their energy source. Carbs also give our cells structure, form part of our genes and play a part in the function of some proteins. On top of this, good carbs serve up a swag of the micronutrients we need for good health including vitamins B, C and E; minerals such as magnesium, potassium and calcium and antioxidants including the carotenoids that play a protective role in eye health.

Why does low GI matter?
Here at GI News, we recommend putting good carbs on the plate, and where possible, choose those with a low GI or GL. Why? There’s high-level evidence that switching to low GI good carbs that trickle the glucose into the bloodstream can help us cut cravings; feel fuller for longer; stay in shape better by minimising body fat and maximising muscle mass; and decrease our risk of some chronic diseases such as type 2 diabetes and heart disease.

When we eat carb-rich foods (fruit, starchy vegetables, legumes, grains, or dairy products such as milk or yoghurt) our bodies convert their sugars and/or starches into glucose during digestion. However, our bodies do this at very different rates and this is where using the glycemic index (GI) helps us make better choices for long-term health and wellbeing. The GI is particularly useful for people who need to manage their blood glucose levels (BGLs). Think of it as a carbo speedo that gives us an idea how quickly our bodies will digest particular carb foods and how fast and high our BGL is then likely to rise.

High GI: 70 and over • Medium or moderate GI: 56 to 69 • Low GI: 55 and under

Why does it matter how high our BGLs go?

As with blood pressure, there’s a healthy range and a risky range. Having BGLs in the normal range over the day is good for our bodies because it also will lower our day-long insulin levels. Having high BGLs from eating too many high GI foods can put pressure on our health, because it means that our pancreas has to work extra hard producing more insulin to move the glucose into the cells, where it provides energy for the body and brain. It’s never a good idea to overwork or overstress body parts. They can wear out or stop functioning properly. It’s not easy to replace a pancreas.
 The Good Carbs Cookbook
This edited extract from The Good Carbs Cookbook (Murdoch Books Australia) is reproduced with permission. Hugh Ford created the illustration. For more information contact: Isabelle O’Brien, Marketing and Communications Associate, Murdoch Books: 

The Good Carbs Cookbook: Available online and in store in Australia now. Publishes 13 July in the UK and can be pre-ordered online from Amazon and Book Depository. It should also be available on for interested US readers to pre-order from June 1.