Diabetes: The six best types of bread for controlling blood sugar levels - what to avoid

"The fermentation process changes the structure of the carbs, slowing the speed of conversion into glucose," explains Holland and Barrett.

According to the health body, pitta, wholemeal, multigrain, chapatti and rye rank lower down on the GI too.

Other low GI foods include:

• Some fruit and vegetables
• Pulses.

Some low GI foods, such as wholegrain foods, fruit, vegetables, beans and lentils, are foods you should eat as part of a healthy, balanced diet.