Understanding the Glycaemic Index

What is the Glycaemic Index? 
Measuring the effects that different carbohydrate foods have on blood sugar levels can help people with diabetes to better manage their food choices. The Glycaemic Index (GI) is a tool used to achieve this, by describing the way the body digests and absorbs food- low GI foods will have less impact on blood glucose levels after a meal.  

Carbohydrates provide fuel for the body. Once broken down into glucose, they are absorbed into the blood stream, travelling to the body’s cells that need energy – hence why a balanced diet containing carbohydrates is important for everyone. They are taken into the cells in combination with insulin. People without diabetes produce enough insulin to keep glucose levels in a very tight range. People with diabetes usually have either a resistance to the effects of insulin or they produce too little insulin. Diabetes can be controlled by diet, exercise, medication and/ or insulin and must be tailored to the individual. 

Foods that contain carbohydrates include: 

• Breads 
• Breakfast cereals 
• Grains e.g. rice, wheat, barley, etc. 
• Starchy vegetables e.g. potatoes, corn 
• Legumes e.g. beans, lentils, chickpeas, etc. 
• Fruit and fruit juices 
• Milk and yoghurt 

Carbohydrate foods can be ranked according to their Glycaemic Index. There are multiple factors that influence a food's Glycaemic Index, including its cooking method, ripeness, nutrition composition and the level of processing it has had.  

High GI vs Low GI 
The terms ‘low GI’, ‘moderate GI’ and ‘high GI’ are given to foods that fall within different ranges of the Glycaemic Index. High GI is when carbohydrate foods are broken down and absorbed quickly, raising the blood sugar level faster and higher. Low GI is when carbohydrate foods are digested and absorbed more gradually, causing a slower, longer-lasting rise in blood sugar levels.  

The three categories of GI consist of: 

High GI (More than 70) – e.g. potatoes and white bread 

Moderate GI (Between 55 and 70) – e.g. orange juice, wholemeal bread, sugar 

Low GI (Below 55) – e.g. soy products, beans, fruit, milk, pasta, oats and lentils 

Research has shown that people eating a lower GI diet can reduce their average blood glucose levels. In aged care, this means that a more relaxed dietary approach can be implemented. Remember that sugar has a moderate GI. The amount of sugar in an average dessert or piece of cake is only small, and ordinary desserts and snacks can be offered, especially if higher fibre (and lower GI) ingredients are used. The main meal (eg a large serve of rice) might have a greater impact on blood glucose levels after a meal! 

Implementing a Low GI approach 
To achieve a low GI diet, individuals should try to include at least one low GI food at each meal. Eating a high GI food together with a low GI food will lower the GI of the whole meal. Including a number of low GI foods on the menu will mean that individuals are likely to choose these important foods. 

Here are some ideas of low GI foods to include on the menu: 

• Offer grain breads if tolerated 
• Porridge, Allbran, natural muesli or Weetbix are good choices at breakfast 
• Fruit loaf or raisin bread are great at breakfast or as a snack 
• Use lower GI varieties of rice 
• Pasta is low GI and can be served as a as part of the hot meal or in a salad 
• Serve baked beans at breakfast or a light meal 
• Add legumes e.g. lentils, beans, chick peas to soups 
• Add legumes to stew and casserole dishes, and mashed into meat patties or meat loaf 
• Serve sweet potato and sweetcorn regularly 
• Serve fruit as a snack, as part of the dessert and on cereal 
• Milk and dairy desserts are low GI and should appear regularly on the menu 

Remember that both the amount of carbohydrate eaten as well of the GI of the food will both have an impact. 

For more information, please visit our resources page or get in touch with one of our Accredited Practising Dietitians today.