Vitamin A is a group of similar molecules that includes retinol, retinal, and retinoic acid. Beta-carotene is a precursor to vitamin A that first needs to be converted to retinal by the enzyme BCMO1. If your copies of BCMO1 have non-functional polymorphisms, then beta-carotene will not be used to make Vitamin A and you must get it in your diet through animal sources or supplementation.

http://www.ncbi.nlm.nih.gov/pubmed/20599666




23andMe assesses 22 snps on the gene BCMO1. Of these, several have been implicated in decreasing BCMO1 activity:

rs12934922
rs7501331
rs6420424
rs11645428
rs6564851

http://www.ncbi.nlm.nih.gov/pubmed/22113863
http://www.ncbi.nlm.nih.gov/pubmed/1...?dopt=Abstract
http://www.ncbi.nlm.nih.gov/pubmed/2...?dopt=Abstract

Vitamin A metabolism is a complex topic with many genes involved, however BCMO1 is critical for us to form useable vitamin A from beta-carotene. If your versions of the gene have risk alleles present, then your requirement for Vitamin A may be increased and supplementation may be wise.