Phytochemicals are natural compounds found in plants that contribute to their color, flavor, and disease resistance. These substances are not essential nutrients like vitamins and minerals, but they can have beneficial effects on human health. Common sources of phytochemicals include fruits, vegetables, whole grains, and legumes. There are thousands of different phytochemicals, and they are often categorized into groups such as flavonoids, carotenoids, and glucosinolates. Research suggests that consuming a diet rich in fruits and vegetables containing these compounds may help reduce the risk of chronic diseases, including heart disease and certain types of cancer.