I read the same reports about microwaving too, but after doing some digging I found that the way the microwaving was done in the quoted study was probably the reason for the poor nutrient retention.

To prevent excess nutrient loss, it's recommended that you don't cook nightshades or other vegetables for extended periods.

Medically reviewed by Kristy Del Coro, MS, RDN, LDN Tomatoes, peppers, eggplants, and white potatoes are all what's known as nightshade vegetables. They belong to a plant family called the ...