Nutrition: A spoonful of sugar helps the exercise go down

Nutrition: A spoonful of sugar helps the exercise go down (MJorge, Flickr.com)

Sugars seem to have got a bad press in recent years. Yet they have an important function in a cyclist's diet – they are the basic building blocks of all carbohydrates.

When used during racing they can delay fatigue and improve performance. Use them during training sessions and they can help prevent overtraining, consume them immediately after exercise and they will replenish muscle glycogen quickly and effectively.

There are many sugars available, but which are best and when? First, we need to classify sugars into their categories:

Monosaccharides: These are the most basic forms of sugars and are always singular types of sugar. You can find these in sports foods in the form of glucose, fructose and galactose.

Disaccharides: these sugars are formed by two monosaccharides bonding. Examples of these are lactose, found in milk, sucrose and maltose.

Polysaccharides: these are long chains of sugars bonded together. Examples are maltodextrin and any starch, such as potatoes or wheat.

Here are the main sugars in your sports drinks and foods:

Glucose: Probably the most common sugar in sports drinks and foods. It can be used directly by the muscles as energy and is one of the few fuels for the brain. The human body absorbs around 60g of glucose per hour, but if a drink has too much glucose in it (more than eight percent) then the absorption of water can be slowed. You’ll find glucose naturally in fruits and vegetables.

Fructose: A naturally occurring sugar you’ll find in fruits. It’s absorbed directly by the intestine but the liver has to convert it into lactate before the muscles can use it as energy. This means fructose is used by the muscles more slowly than glucose. However, fructose has its own transporter in the intestine, so if you add fructose to a glucose drink you’ll actually increase the amount of ingested sugars used as fuel during exercise to around 90g per hour. Mixtures of glucose and fructose have been shown to improve performance over a glucose-only drink by eight percent. Some people have fructose intolerance when large amounts are ingested, causing diarrhoea.

Sucrose: More commonly known as table sugar, this is a disaccharide, made up of glucose and fructose. You’ll find natural forms of it in fruits and vegetables.

Lactose: A disaccharide made up of galactose and glucose. You’ll find lactose in milk and dairy products. It’s not usually used in sports drinks, but you might find it in recovery drinks. Some people are lactose intolerant, so should avoid lactose-containing products.

Maltodextrin: A polysaccharide made up of long chains of glucose molecules which is used by the muscles at the same rate as glucose. The advantage to maltodextrin over glucose is that fluid absorption doesn’t decrease at large concentrations (greater than eight percent).

Sweet secrets

Use this list to discover what’s hidden in your sports drink...

1 Look for the total carb content in nutritional information. The total amount of carbohydrate in grams per 100ml of the drink gives you the concentration of the drink. Make sure this is below eight percent.

2 The starch content of the drink will tell you how much maltodextrin there is in it. The sugar content is likely to consist of glucose, fructose or sucrose.

3 Look at the ingredients list. By law, ingredients must be listed in order, starting with the largest amount of an ingredient and working its way down to the lowest.

4 Look out for drinks with a mixture of maltodextrin or glucose as the first ingredient (after water) with some fructose included, as fructose helps you use sugar. If fructose is low down there won’t be much of it.

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