Apples are a source of both soluble and insoluble fiber. Soluble fiber such as pectin actually helps to prevent cholesterol buildup in the lining of blood vessel walls, thus reducing the incident of atherosclerosis and heart disease. The insoluble fiber in apples provides bulk in the intestinal tract, holding water to cleanse and move food quickly through the digestive system. It is a good idea to eat apples with their skin. Almost half of the vitamin C content is just underneath the skin. Eating the skin also increases insoluble fiber content. Most of an apple's fragrance cells are also concentrated in the skin and as they ripen, the skin cells develop more aroma and flavor. Grown in temperate zones throughout the world and cultivated for at least 3,000 years, apple varieties now number well into the thousands. Apples range in color from lemony yellow to bright yellow-green to crimson red. Their textures range from tender to crisp, their flavors from sweet to tart and from simple to complex. They're available year-round but are at their best from September through November when newly harvested. Apples are a good source of vitamins A and C.