Only chestnuts and cashews have a glycaemic index (GI) rating, as these are the only two nuts that contain enough carbohydrate to be GI tested. Chestnuts have a GI of 54, and cashews have a GI of 25 – both are low. 

The Glycaemic Index (GI) is a relative ranking of carbohydrate in foods according to how they affect blood glucose levels. For foods to be measured for their GI, they need to contain a certain amount of carbohydrate. With the exception of chestnuts and cashews, nuts don’t contain much carbohydrate and so do not have a GI.

However, nuts have a GI-lowering effect reducing the overall GI of a meal. That is, when nuts are mixed with foods rich in carbohydrates, they slow the digestion of the meal resulting in a slower rise in blood glucose [1]. This is because nuts are complex structures which takes time to digest, slowing the whole passage of food through the intestine and slowing the rise of blood glucose after a meal.

Low GI foods are digested and absorbed more slowly, causing a slow rise in blood glucose which means better type 2 diabetes control and better appetite control. A low-GI diet has been shown to reduce the risk of type-2 diabetes and help in its management [2].