A substance that is converted into a vitamin, such as 7-dehydrocholesterol, which is converted into vitamin D, or those carotenes that can be converted to vitamin A.
A chemical compound which is converted to a vitamin during usual biochemical processes, e.g. the amino acid tryptophan, which is converted to niacin, and beta carotene, which is converted into vitamin A.
Substance that in the body may be converted into a vitamin; a vitamin precursor.
A substance that is not itself a vitamin but can be convened to a vitamin in the body. An example is β-carotene, which can be converted into vitamin A.
An inactive substance that can be transformed in the body to a corresponding active vitamin and thus function as a vitamin.
Certain vitamins exist in a state of inactivity within foods, yet upon entering the body, they undergo conversion into their active forms.