Has the G.I. factor been tested in long-term studies?
At least twelve studies to date have looked at the G.L factor in the diet in relation to long-term diabetes control. Some of these studies have been five weeks long, others, including ours, up to three months. All but one showed a clear benefit in improving blood sugar levels. People with high blood lipids (cholesterol, triglycerides) showed improvements in this area as well.
The insulin response is important and the G.L factor does not tell us anything about this. Is there a correlation?
In general, studies have found an excellent correlation between the G.L factor of a food and its insulin response. Sometimes the insulin response is higher or lower than expected. The presence of more protein will increase the insulin response proportionately. A large amount of fat may reduce the glycaemic response but not the insulin response. But we should be avoiding large amounts of fat.
Why do different groups around the world come up with different values for the same food?
For the most part, we see very reproducible G.L factors for the same foods from standardised tests around the world. Apples and oranges, for example, have been tested a great deal and give similar G.L factors.
Packaged foods like cornflakes also give very consistent values.
Rice is one food which is very variable because its amylose content varies from variety to variety. Oats and porridge vary, too. To date we are not sure of the reasons for this. Potatoes vary with the variety and method of cooking. New or cocktail potatoes have lower G.L values.
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