While most people think of citrus fruits as the best source of vitamin C, vegetables also contain high levels, especially peppers, broccoli, and Brussels sprouts. Vitamin C is destroyed by exposure to air, so eating fresh foods as quickly as possible is best. Although a salad from a salad bar is a healthy lunch choice, the vitamin C content of the fruits and vegetables is only a fraction of what it would be if the salad were made fresh. For example, freshly sliced cucumbers, if left standing, lose between 41 and 49 percent of their vitamin C content within the first three hours. A sliced cantaloupe, left uncovered in the refrigerator, loses 35 percent of its vitamin C content in less than twenty-four hours.