According to the nutritional guidelines adopted by the United States Department of Agriculture, 2-4 servings of fruits a day is needed to maintain good health. Fruits such as apples and oranges are low in calories and fat, and are a good source of natural sugars, fibers, vitamins, and phytonutrients. Phytonutrients such as flavonoids are plant chemicals that are thought to promote human health, Large population (epidemiological) studies have shown fruit and vegetable consumption decrease the risk of stroke, heart disease, and certain cancers.