Q. Does roasting vegetables at high temperatures, such as 425 degrees Fahrenheit, destroy nutrients in the vegetables?
A. Katelyn Castro, a dietetic intern at Tufts' Frances Stern Nutrition Center, responds: "The caramelization that occurs during the roasting process can enhance the flavor of vegetables and increase your enjoyment of them. However, roasting vegetables has some nutritional trade-offs. Cooking vegetables increases the availability of some nutrients, such as beta-carotene and lycopene, by breaking down plant foods’ cell walls. At the same time, roasting vegetables can reduce levels of heat-sensitive nutrients, such as vitamin C and folate."
Nutrient loss with heat is not unique to roasting. Other forms of cooking can also reduce heat-sensitive nutrients, and cooking methods that use water, such as boiling, result in nutrient losses from water-soluble nutrients leaching into the water. "So, consider varying your preparation methods, such as by eating raw vegetables and salads as well as roasted, steamed or sautéed vegetables."