Can you reduce the GI of a meal by adding protein or fibre?

Yes, you can!

Adding Protein:

Protein slows stomach emptying and therefore carbohydrate digestion, producing a smaller blood sugar raise and lowering the GI.

Examples of carbohydrate/protein combinations include beans, lentils, peas and past (all of these contain both protein and carbs). Eating chicken with rice also lowers the GI.

The addition of other foods that contain fibre or fat will also reduce the GI of a meal. The GI of this "mixed meal" can be estimated by taking a weighted average of the GI's of the individual foods in the meal.

Adding Fibre:

Fibre, in particular soluble fibre, can also decrease the GI of a meal.

Soluble fibre increases the viscosity of food in the digestive tract and slows digestion, producing lower blood sugar rise and lowering the GI.
Examples of foods with a high soluble fibre content include beans, lentils, peas, oats, porridge, barley, and fruit.

AUTHOR: Alex Ruani, Research Director

Updated on: 15/10/2026