How is vitamin A synthesized naturally?

Answer 1

The term "vitamin A" makes it sound like there is one particular nutrient called "vitamin A," but that is not true. Vitamin A is a broad group of related nutrients.

There are two basic forms of vitamin A: retinoids (found in animal foods) and carotenoids (found in plant foods). Carrots, tomatoes, leafy greens, sweet potatoes, and margarines colored with beta-carotene are found in the top 10 provitamin A-containing foods.

About two-thirds of all vitamin A intake from food comes in the form of retinyl esters found in animal products like butter, cheese, eggs, and organ meats like liver are among the top 10 sources of vitamin A.

As for how they are made by plants and animals that have them, the abstracts begin like this: "Carotenoids represent one of the most widely distributed and structurally diverse classes of natural pigments, with important functions in photosynthesis, nutrition, and protection against photooxidative damage. In the eubacterial community, yellow, orange, and red carotenoids are produced by anoxygenic photosynthetic bacteria, cyanobacteria, and certain species of nonphotosynthetic bacteria. Many eukaryotes, including all algae and plants, as well as some fungi, also synthesize these pigments." And that is just the start. You will need a couple of classes in Biochem to understand.