To get the greatest health benefit from your food, maximize the nutrient and phytochemical content and minimize potential hazards:
Choose fruits and vegetables in season -- organic if possible to avoid residual pesticide. Produce that looks the freshest probably has the highest nutrient value.
Peel produce only when necessary and remove as little peel as possible. Many nutrients are in or near the skin.
Use fresh or frozen produce rather than canned because some phytochemicals are destroyed in the canning process.
Raw or lightly cooked vegetables and fruits have more cancer-fighting chemicals than those cooked a long time. (The exception to this is lycopene, a phytochemical in tomatoes that is absorbed better when the tomatoes are cooked.)
When using garlic in a recipe, wait ten minutes after chopping to cook it. It takes time after chopping the garlic for the cancer fighting chemicals to be fully released and heat can stop the process.
To preserve nutrients, cook in a small amount of water or stir-fry in a small amount of oil.
Vegetables can be cooked in the microwave with a little water. Microwave frozen vegetables with no additional water.
Use glass containers in the microwave. Chemicals from plastic containers or plastic wrap may end up in your food.
Cook with olive or canola oil instead of butter, margarine, or other oils. Try baking with them also, or reduce the amount of fat in the recipe.
Use whole grains instead of refined. Try substituting some whole wheat flour for white flour in your favorite recipes.