﻿ Glycaemic Index (GI) - Diabetes UK

Glycaemic Index (GI)

The Glycaemic Index (GI) is a ranking of carbohydrate-containing foods based on the overall effect on blood glucose levels. Slowly absorbed foods have a low GI rating, while foods that are more quickly absorbed have a higher rating. This is important because choosing slowly absorbed carbohydrates, instead of quickly absorbed carbohydrates, can help even out blood glucose levels when you have diabetes.

Foods are given a GI number according to their effect on blood glucose levels. Glucose is used as a standard reference (GI 100) and other foods are measured against this

A review of research (a Cochrane Review) showed that HbA1c can be lowered by 0.5 per cent in people with diabetes who adopted a low GI diet (although the majority of studies were related to people with Type 2 diabetes).

  • Some studies have shown people who have a high GI diet tend to have higher HbA1c levels.
  • Two recent trials have shown following a low GI diet has no benefit compared to following the American Diabetes Association dietary education.
  • Slow-acting carbohydrates reduce the peaks in blood glucose levels that follow a meal, and this may have a role in helping to prevent or reduce the risk of developing Type 2 diabetes.
  • Research has shown that lower GI diets have also been associated with improved levels of ‘good’ cholesterol and a lower incidence of heart disease.

Factors that may affect the GI of a food include:

  • Cooking methods: frying, boiling and baking.
  • Processing and the ripeness of fruit and certain vegetables.
  • Wholegrains and high fibre foods act as a physical barrier to slow down absorption of carbohydrate. This is not the same as ‘wholemeal’, where, even though the whole of the grain is included, it has been ground up instead of left whole. So some mixed grain breads that include wholegrains have a lower GI than either wholemeal or white bread.
  • Fat lowers the GI of a food. For example chocolate has a medium GI because of its fat content and crisps will actually have a lower GI than potatoes cooked without fat.
  • Protein lowers the GI of food.
  • Milk and other dairy products have a low GI because of their high protein content, and because they contain fat.



Educating yourself on GI






How do I lower GI?

  • Choose basmati or easy cook rice, pasta or noodles.
  • Switch baked or mashed potato for sweet potato or boiled new potatoes.
  • Instead of white and wholemeal bread, choose granary, pumpernickel or rye bread.
  • Swap frozen microwaveable French fries for pasta or noodles.
  • Try porridge, natural muesli or wholegrain breakfast cereals.
  • You can maximise the benefit of GI by switching to a low GI option food with each meal or snack.