Provitamin A is largely spared from ill effects, although it's the beta-carotene found in carrots that is responsible for the peculiar orange-tinted look people who jump on fad diets heavy on carrots get.
The three types of carotenoids that humans can convert into vitamin A are beta carotene, alpha carotene and gamma carotene, all three of which are sometimes referred to as provitamin A.
The provitamin A carotenes, especially beta-carotene, are known for the role they play in promoting good vision, especially night vision.
It comes in two forms; preformed vitamin A, and provitamin A, a precursor that becomes vitamin A in the body once ingested.
This form of vitamin A, known as provitamin A, carotene or beta-carotene, is water soluble and is not stored in the body.