Vitamin C also know as ascorbic acid, has a number of important functions to our body such as helps protect cells and keeps us healthy and helps the body absorb iron from food. Vitamin C is a water-soluble vitamin, which means you need it in your diet every day because it can't be stored in the body. An adult need 40 mg a day and taking large amounts of vitamin C can cause stomach pain, diarrhea and flatulence. But these symptoms should disappear once you stop taking the supplements. Vitamin C is found in a wide variety of fruit and vegetables. Good sources include peppers, broccoli, Brussels sprouts, sweet potatoes, oranges and kiwi fruit.