The Glycaemic Index (GI) is a ranking system that measures how quickly carbohydrate-containing foods raise blood glucose levels compared to pure glucose. Developed in the early 1980s by Dr David Jenkins at the University of Toronto, it has become one of the most widely used tools in nutritional science.
How GI Is Measured
Foods are scored on a scale from 0 to 100. Pure glucose is the reference point at 100. Foods are tested by having volunteers consume a portion containing 50 g of digestible carbohydrate, with blood glucose measured over two hours.
- Low GI (55 or below): Vegetables, legumes, oats, most fruit, whole grain bread
- Medium GI (56–69): Wholemeal bread, brown rice, raisins, boiled potatoes
- High GI (70+): White bread, white rice, cornflakes, baked potato
Why GI Matters for Blood Sugar Control
Choosing lower-GI foods slows digestion, producing a gentler, more sustained release of glucose into the blood. Research consistently shows that low-GI diets are associated with improved HbA1c levels, reduced cardiovascular risk, and better appetite control.
Practical Swaps to Lower Your Dietary GI
- Replace white rice with basmati or brown rice
- Choose whole grain or sourdough bread over white bread
- Eat pasta al dente — overcooking increases GI
- Add vinegar or lemon juice to meals — these slow gastric emptying
- Snack on nuts and seeds rather than crackers or rice cakes
