Retinol is part of a group of compounds called Retinoids that are derived from Vitamin A. Vitamin A is found in the liver, as well as in fish like cod and sardines, many vegetables and certain non-citrus fruits. Vitamin A is known to help improve eye and skin health, as well as boosting the immune system, playing an essential role in fetal development, and having potential in cancer prevention—although overdosing can also be dangerous.
There are lots of different types of Retinoids, from stronger prescription Retinoids with a higher risk of side-effects, to weaker variations used in over-the-counter skin products. These are used in topical applications (creams and gels), as well as in oral medication and food supplements.