The GI Index

Glycaemic Index Tables

That is probably the most comprehensive GI index i have seen on the internet.

How is the GI worked out?

The GI value of a food is worked by out by feeding 10 or more healthy people a portion of food containing 50g of carbohydrate. For example, you would eat a 250g baked potato which contains 50g carbs. Over the next 2 hours a sample of blood is taken every 15 minutes and the blood sugar level is measured. On another occasion, the same 10 people consume 50g of glucose. Their response to the potato is compared with their blood sugar response to 50g of glucose.

50g of glucose equates to 100 on the GI index.

Glucose is used as the yardstick to measure everything against. A baked potato registers as 85 which means it produces a rise in blood sugar which is 85% as great as that produced after eating an equivalent amount of glucose.

So how do i integrate the GI Index into my diet?

Use the GI Index to select mainly low GI carbohydrate. Low GI should make up the bulk of your carbohydrate intake, with the exception of post workout where high GI carbs may come in handy (more on that later).

What are the drawbacks of the GI?

The biggest drawback is that GI Index doesn't take account of the portion size you are eating, For example, watermelon has a GI of 72 which makes it high, which would make it a no-no for the low GI seekers. However an average slice (120g) only contains around 6g of carbs. So you would need to eat around 8 slices to obtain around 50g of carbs - the amount used in the GI test.

Also many (not all) vegetables appear to have a high GI value. However their carbohydrate content is so low that you would have to eat an absolute mountain of it for it to have any significant effect on blood sugar.

Another drawback is that some foods that are high in fat have a low GI value. The GI of crisps or chips is lower than the GI of a baked potato. Fat reduces the rate at which food is digested but saturated and trans fats can push up heart disease risk.

The bottom line is this - Don't just select foods by their GI value. Check out their protein and fat content aswell. Watch out for saturated and trans fats!