Many vegetables are best eaten raw. Some need to be cooked to be digested better (a potato for example). Some of the nutritional value of vegetables will be lost by cooking, vitamin C, for instance is destroyed by heat, so the longer you cook, especially at high temperatures, the less vitamin C remains. Eating overcooked food of any sort, especially when burnt, is not good for you. The DNA or protein in foods must be broken down by your digestive system to be absorbed, so in normal cooking of foods the change that happens with DNA and protein typically wont effect its nutritional value.
Chef Sanjeev Kapoor is the most celebrated face of Indian cuisine. He is Chef extraordinaire, runs a successful TV Channel FoodFood, hosted Khana Khazana cookery show on television for more than 17 years, author of 150+ best selling cookbooks, restaurateur and winner of several culinary awards. He is living his dream of making Indian cuisine the number one in the world and empowering women through power of cooking to become self sufficient. His recipe portal www.sanjeevkapoor.com is a complete cookery manual with a compendium of more than 10,000 tried & tested recipes, videos, articles, tips & trivia and a wealth of information on the art and craft of cooking in both English and Hindi.