Health and lifestyle magazines regularly feature the latest fads and different diets. One diet that is of particular interest for people with diabetes is the Glycaemic Index or "GI" diet. This is because of the claims that it can influence blood glucose levels.
The GI diet is a ranking of foods based on the rate that they raise blood glucose levels. The ranking starts at zero and finishes at 100, with pure glucose (sugar) giving a baseline GI of 100. Foods that break down in your body quickly, raise your blood glucose levels swiftly and are given high GI values. Whereas foods that breakdown slowly and are slower to increase blood glucose levels, are given low GI values. Different foods are sometimes ranked as high, medium or low GI. Foods with a GI value of 70 or more are considered high, 56-69 are average or medium, and 55 or less are low.
While this system may seem simple, it has its complications. For example, you would need to eat an unrealistically large portion of certain foods with a high GI value (such as carrots) for them to raise your blood glucose level. Also, the amount of fat added to your food affects the rate it is absorbed. If you add oil or margarine to a baked potato, you will lower the GI ranking, because fat affects the GI value of carbohydrate foods. Working out the GI value of a whole meal from a GI food table isn't always easy.
The GI is very useful for replacing one food item with another. For example, it might be a good idea to replace potatoes (GI: 85) with pasta (GI: 46-52) for your evening meal, because this will help reduce your risk of developing night-time hypoglycaemia.The GI is also very useful for choosing snacks between meals. It may seem obvious which would be the most suitable snack between an apple and a bag of jelly sweets. However, faced with a choice of peanuts or a low-fat yoghurt, would you know which had the lower GI value? The answer is peanuts.
There is good scientific evidence to suggest that a diet rich in low GI foods can help reduce your HbA1c level when compared with other more conventional diets. The GI diet could therefore be useful for understanding how your blood glucose level can be controlled and managed through your diet. However, more research is needed before GI will be recommended as a general tool in diabetes care. Speak to your diabetes healthcare team for more advice about how different foods affect your diabetes.