Nutrition Science and Everyday Application - beta v 0.1

Vitamins Important for Vision
Vision is one of our five basic senses, and unless you’ve experienced vision loss, it’s hard to
imagine life without sight. Vitamin A plays a key role in vision and eye health. On this page,
we’ll cover the functions, food sources, and signs of deficiency and toxicity for vitamin A and
carotenoids such as beta-carotene, which can be converted to vitamin A.
VITAMIN A
Vitamin A is a generic term for a group of similar compounds called retinoids. Retinol is
the form of vitamin A found in animal-derived foods, and it is converted in the body to the
biologically active forms of vitamin A: retinal and retinoic acid. The dietary retinol found in
animal-derived foods is called preformed or active vitamin A.
This differentiates it from beta-carotene and other carotenoid compounds, which are
brightly-colored yellow, orange, and red pigments synthesized by plants. These are called
provitamin A carotenoids, because they can be converted to vitamin A in the body. Among
the carotenoids, beta-carotene is most efficiently converted to vitamin A. If you look at
the beta-carotene molecule, you can see that it looks like two retinol molecules connected
together. Enzymes in the intestine and liver can cleave the beta-carotene molecule in half,
creating two new molecules of vitamin A.
486