Carbohydrate foods (i.e. grains, cereals and fruit) are broken down to glucose, which provides energy for our bodies. The Glycaemic Index (GI) indicates how quickly different carbohydrate foods raise our blood glucose levels, ranking foods numerically, from 0 to 100.
Carbohydrate foods that are readily digested and cause blood glucose levels to rise quickly are called high GI foods (they have a value greater than 70). Foods that are broken down slowly and provide a more sustained supply of energy are called low GI foods (these have a value less than 55).
Foods with a lower GI break down more slowly during digestion, giving a slower and more even rise in blood glucose levels, helping to sustain our energy levels for longer. Foods with a higher GI break down the fastest during digestion. High GI foods are useful for some groups of people, such as athletes, who need a fast supply of glucose to fuel their muscles during and after competition.