DefinitionThe glycemic index ranks carbohydrate foods from 0 to 100 by how quickly they raise blood sugar compared with pure glucose, which scores 100.
What it means
MedlinePlus groups foods into three bands:
- Low GI, 55 or less: most fruits, non-starchy vegetables, beans, lentils, rolled or steel-cut oats, milk and yogurt
- Medium GI, 56 to 69: foods such as brown rice, couscous and rye bread
- High GI, 70 or more: foods such as white bread, white rice, potatoes and many processed cereals
Fat, fiber, protein, ripeness and cooking all change how fast a food raises blood sugar. Foods with little or no carbohydrate, such as meat and oils, do not have a GI value.
GI does not reflect portion size. Glycemic load adjusts for the amount of carbohydrate in a typical serving, which is often more useful in daily life.
For weight loss, total calories and protein matter more than GI. For people with diabetes, pairing higher-GI foods with protein or fiber can soften blood sugar spikes.
Why it matters
GI is a useful tool for steadier blood sugar, but it does not replace calorie and protein targets.