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I love to roast all different kinds of vegetables, such as broccoli, asparagus, peppers, green beans, zucchini, etc. I think it gives them a great flavor. I have read that when you roast or cook vegetables, they lose their benefits, that you should only steam vegetables. Is this true?
Vegetables begin to lose nutrients from the moment they are harvested. This is particularly true of vitamins and antioxidants. Likewise, cooking veggies reduces some nutrients. There's been a lot of research on the different methods of cooking and some of the studies are in conflict. It does appear that steaming, stir frying, and roasting are better than boiling. The difference in nutrients lost ranges from about 20 to 40 percent for steaming, stir frying, and roasting and as much as 50% for boiling.
I believe that the key is to get as many fruits and veggies in your diet as possible and to mix up the different methods of cooking. Eat salads and raw veggies, steam them, roast them, and even stir fry. You'll lose some nutrients by cooking, but if you love roasted veggies, you're more likely to eat them (possibly more likely when there's more variety as well).
So enjoy your roast veggies and enjoy them often.
Thanks for writing.
Timothy S. Harlan, MD, FACP