I remembered reading in an article ages ago that the method of cooking potatoes has an impact on their glycemic index – steaming better than boiling better than baking, iirc (microwaving might have been the best of the lot).
Just took a quick look for the impact of cooking, cooling, and reheating carbs on resistant starch, and it looks like the rice result extends to wheat and potatoes too.
(Might explain the prevalence of par-boiled starches in various ancient cultures – rice of various sorts in south India, wheat products like bulgur in the middle east, and so on.)
