Does microwaving fruits & vegetables kill all the nutrients?

When cooking veggies, microwaving is actually a good way to minimize the loss of nutrients. The nutrients of most concern when microwaving are the water-soluble vitamins: vitamin C and the B vitamins. These vitamins are lost more easily during the cooking process, because they easily move into the cooking water. The fat-soluble vitamins (A, D, E, and K) are not easily lost to the water during the cooking process.

A review in the Journal of Food Composition and Analysis found higher retention values of water-soluble vitamins in foods that were prepared in the microwave, steamed, or stir-fried. Vitamin C in spinach and green beans cooked in the microwave had a mean retention of up to 79% when compared to 66% retained when boiled. Another study cited in the article found that retention of vitamin C was the highest in fresh broccoli, cauliflower, potatoes, frozen corn, and peas cooked by microwave steaming, followed by microwave-boiling, stovetop steaming, and stovetop boiling. Folate, vitamin C, retinol (a from of vitamin A), and thiamin (B1) seem to be most affected by the cooking process.*

The difference in nutrient quality caused by cooking (including microwaving) is very minimal. The most important thing is that you are eating your fruits and veggies. No matter how you prepare them, or what form you prefer, consuming fruits and vegetables is much more beneficial to you than not consuming them at all.

* Leskova, Emila, et al. “Vitamin Losses: Retention During Heat Treatment and Continual Changes Expressed by Mathematical Models.” Journal of Food Composition and Analysis (2006); (19) 4: 252-76.