Many people believe that fresh fruits and vegetables always contain more nutrients than cooked ones, but cooked carrots have higher levels of antioxidants than fresh carrots. Cooking carrots in the presence of a small amount of oil or butter increases the amount of two antioxidants called beta carotene and phenolic acid. Cooking also increases the amount of lycopene you get from tomatoes. Cooking breaks the plant cells open to increase the absorption of these antioxidants and other beneficial plant chemicals. Adding a little oil or butter increases absorption of fat soluble chemicals.
Some vitamins are affected by cooking, but you'll still get plenty. The enzymes in food that are destroyed by heat are of no use to you; your body makes the enzymes you need to digest your food. Most of the nutrients in food (minerals, proteins, fats, carbohydrates) are not destroyed by heat, and many common foods are unpalatable or unsafe if they are not cooked. I recommend eating the widest possible variety of fruits and vegetables, raw or cooked, and fresh, frozen, canned or dried. For more on food enzymes see report #1451