When consumed on an empty stomach, ascorbic acid has a high acidity and may cause some gastrointestinal adverse effects. Calcium ascorbate (neutralized vitamin C) has been produced to alleviate the epigastric side effects of ascorbic acid's low pH. The calcium salt does not appear to have any additional benefit over un-neutralized vitamin C. Ascorbic acid is also used as a medication. It can be given by mouth in doses of 1 g per day. As a supplement, 100 mg three times a day is recommended. Higher doses may cause diarrhea, nausea, and abdominal pain. Vitamin C was first discovered by Albert Korsinsky in 1916. He obtained it from cultures of various plants and fruits including citrus fruits, strawberries, tomatoes, and potatoes. Today, most vitamin C comes from frozen concentrated green vegetables such as broccoli, cauliflower, and brussels sprouts. Vitamin C exists in two forms: ascorbic acid and dehydroascorbic acid. The body can convert some dehydroascorbic acid into ascorbic acid but not all of it. This means that you will still be taking up oxygen even when your blood levels are high enough for them to be considered "normal." Vitamin C is essential for strong healthy teeth and bones. It helps fight infection with other nutrients such as zinc and selenium.