Formerly known as Vitamin B15 it is no longer considered to be a vitamin. An energy supplement marketed mainly for racehorses it purports to boost athletic performance, endurance, and recovery by enhancing oxygen utilization and reducing muscle lactate levels. It was also touted as supporting and enhancing the immune system.
Whilst some initial studies indicated beneficial effects these were not supported in later, better constituted trials and the product has largely fallen out of favor. There seems little scientific evidence to support its use.