Black rice has a glycemic load of 12.25, while red rice and white rice each have a glycemic load of 17.75, indicating that despite differences in glycemic index, the three rice varieties deliver similar amounts of glucose per typical serving due to comparable carbohydrate content.

The outer layers of black rice contain fibers and natural compounds that block digestive enzymes from breaking down starch quickly, so glucose enters the bloodstream slowly. Red rice has the same fibers and compounds, but cooking it for a long time melts the starch structure, letting enzymes break it down fast. White rice has no outer layers, so enzymes break down its starch quickly. All three types have nearly the same amount of starch, so they release the same total amount of glucose, but black rice does it slowly and red and white rice do it fast.