is a a water-soluble antioxidant
, used mainly as an ingredient in the kind of soft drinks your dentist
warns you not to drink. It is a stereoisomer of ascorbic acid
and is used in the same way in most cases.
It is also known by the names isoascorbic acid and D-araboascorbic acid.
It is used mainly to preserve freshness, because we all know a Mountain Dew is better right out of the vats.
It has no known mutagenic or carcinogenic properties, and has not been shown to inhibit the uptake of any vitamins or minerals. It uses similar uptake paths to ascorbic acid in the body, but does not give the benefits of that vitamin.
It's kosher as well, so drink up!