Most food preparation, including chopping, cooking, baking, juicing, and so on, actually reduces the nutritional value of the food. Cooking food damages some of the more delicate nutrients. The barbecue adds lots of flavor but that delicious charcoal flavor that makes it so distinctive comes at the cost of added carcinogens. Even something as simple as chopping diminishes the nutritional value of produce. This is just part of eating, and unless you're going to eat entirely raw foods, it's something you minimize where possible and learn to live with. Cooking minimally, chopping things right before you eat them, and eating as raw as you can are some good and easy strategies for dealing with this challenge.