The colorful skin of an apple, grape or tomato is certainly chockfull of nutrients. But by no means are the outer layers of most fruits and vegetables the prime source of their nutrition.
Part of what makes some fruits and vegetables so rich with color – wax and pesticides notwithstanding – are pigments in the skin that have healthful antioxidant properties. Resveratrol, for example, is found in the skin of red grapes and other fruits. But lycopene, one of the pigments that gives tomatoes and bell peppers their deep red color, is distributed throughout.
Indeed, many vitamins and nutrients are found in the skin as well as the flesh. Take apples. According to the United States Department of Agriculture, a large red apple with its skin intact contains about 5 grams of fiber, 13 milligrams of calcium, 239 milligrams of potassium, and 10 milligrams of vitamin C. But remove the skin, and it still contains about 3 grams of fiber, 11 milligrams of calcium, 194 milligrams of potassium, and plenty of its vitamin C and other nutrients.