Beta-carotene is often thought of as a form of vitamin A itself.

Retinol is the most active form of vitamin A and it is also converted in the liver from carotenoids.

The study, in Finland, also showed that a form of vitamin A had no effect on reducing cancer.

Tretinoin is a topical form of vitamin A that helps the skin renew itself.

And we know that the fat-soluble form of vitamin A can build up in the body over time to the point of toxicity.

All forms of vitamin A have a beta-ionone ring to which an isoprenoid chain is attached, called a retinyl group.

Retinol, the form of vitamin A absorbed when eating animal food sources, is a yellow, fat-soluble substance.

Researchers have succeeded in creating water-soluble forms of vitamin A, which they believed could reduce the potential for toxicity.

However antioxidants, such as selenium and beta-carotene (a form of vitamin A), help reinforce this protection.

These topical preparations containing a synthetic form of vitamin A can help clear up psoriasis.