Carbohydrates

If you look at the nutrition information on the back of food labels, you’ll see a value for ‘carbohydrate’, while the line below it says ‘of which sugars’.

This information is supposed to help you understand what you’re eating, but does it all make sense?

Carbohydrate is a term which covers sugar and starch. The differences are due to the chemical structure – it can be complicated but we’ll explain the key points here.

Sugar

Sugars occur naturally in all sorts of food, like fruit and vegetables, milk and honey, and they’re also added to processed foods.

There are several different types of sugar but the most useful is glucose (a single sugar ‘unit’) because this is used to fuel your body.

Starchy foods are made up of chains of sugar units and, as they’re digested, the chains are broken and the single sugar units (glucose) are released into the bloodstream. It’s then used to fuel your brain, red blood cells, muscles and every individual cell.

As the glucose enters the bloodstream your blood glucose (or ‘blood sugar’) level rises. The effect food has on blood glucose concentration is known as the ‘glycaemic index’, or GI.

Foods which contain carbohydrate have a greater effect on your GI than fatty foods or protein-rich foods. Those high in sugar have the greatest effect, while starchy foods (particularly wholegrains) tend to be digested more slowly and so release glucose into the blood more slowly.

Extreme highs and lows of blood glucose are bad for your health. Foods and meals with a low or medium GI release glucose into the bloodstream steadily, which makes the release of energy last longer.

Sweet tooth

Problems arise when sugar’s eaten in large quantities, or very often. Not only can it affect your blood glucose levels but it’s easy to consume more than you need for energy. If it’s not used, it can’t be stored as sugar and has to be converted to fat – and the body stores fat very well!

There’s also an effect on dental health, especially for children. Perhaps surprisingly, it’s not necessarily the amount of sugar you consume that causes the problems. The worst damage is done when the sugar is in your mouth for a long time, for example, sucking on hard sweets, chewing sweets that stick to your teeth or making sugary drinks last a few hours. It’s better to eat sugary foods with meals, when the saliva helps neutralise the acid produced by bacteria.

A final point – the sugar in fruit contains the same number of calories as the sugar in a biscuit, for example. So, what’s the difference? Well, fruit also contains vitamins, minerals, antioxidants and fibre. Biscuits also contain fat. There’s no comparison – when you’re feeling the need for a sweet treat, reach for a piece of fruit every time.

Starch

Starchy foods are staples in diets all over the world, and make up an important part of every meal. Bread, potatoes, rice, pasta, breakfast cereals, couscous, plantain, cassava and maize are all good sources of carbohydrate.

Starchy foods provide a good source of energy and contain fewer calories than fat. They’re also packed full of other important nutrients, like calcium, iron and B vitamins.

It’s recommended that starchy foods make up around one-third of your diet. It doesn't mean one-third of every meal – a breakfast of cereal or toast, for example, is high in carbohydrate.

Instead, try thinking about what you eat over the course of a day, or a week. Are your cupboards full of pasta, rice, potatoes and bread, with plenty of fruit and vegetables (remember, fresh, frozen, tinned, dried and juiced all count towards your 5-a-day) and some sources of protein, like fish, lean meat, eggs, tofu, beans and pulses?

Starchy foods also cause your blood glucose levels to rise (as do all foods), but it’s usually slower than with sugary foods because of the extra time it takes to break down the starch. However, some foods are very refined – white bread, or white pasta, for example, and these have a very similar effect to sugar.

In order to slow the release of glucose into your blood it’s best to eat wholemeal or wholegrain starchy foods, which take longer to break down, keeping you fuller for longer and giving you a steady stream of energy.

Fibre

Fibre is a type of carbohydrate, found only in food that comes from plants (so there’s none in meat, fish or dairy products).

There are two types of fibre – soluble and insoluble.

Insoluble fibre is indigestible by humans but doesn’t harm us – in fact, the opposite is true. You need this type of fibre for healthy bowels because it absorbs water as it moves through the bowel, which softens and increases the bulk of the waste and speeds its journey through the bowel.

Eating a diet rich in insoluble fibre will help prevent bowel problems, such as constipation and piles. Research has shown that it can also reduce your risk of developing bowel or colon cancer.

Foods rich in insoluble fibre include wholegrain bread, brown rice, wholegrain breakfast cereals and fruit and vegetables.

Soluble fibre can be partly digested and is very good at slowing the release of glucose into the bloodstream. Porridge, for example, is an excellent source of this type of fibre and is famous for keeping you feeling fuller for longer.

In addition, soluble fibre may also reduce levels of cholesterol in the blood, which may in turn reduce the risk of heart disease.

Oats, beans and pulses are all great sources of soluble fibre.