Vitamin A

Vitamin A refers to a class of compounds called the retinoids. This includes retinol and related compounds, as well as molecules that the body will use to produce retinol, such as the carotenoids. Molecules that the body converts into a useful substance are called precursors. In this case, carotenoids are precursors to retinoids. Retinol is a crucial component of rhodopsin, which is involved in eyesight and vision. Because of this, a deficiency of vitamin A can lead to night blindness. Vitamin A is also involved in cell differentiation, where the body specializes cells for specific functions. Vitamin A specifically helps with the differentiation of epithelial, or skin, cells. Vitamin A also has other roles in cell growth and reproduction, as well as assisting immune function. Major sources of vitamin A are plants that are high in carotenoids, such as pumpkin, carrots, and spinach. Animal liver is also a good source of Vitamin A. It is possible to overdose on vitamin A, a condition called hypervitaminosis A, which results in blurred vision and reduced bone strength. A polar bear’s liver contains a lethal dose of vitamin A. The association between vitamin A, vision, and carrots as a source of carotenoids led to the idea that carrots are good for eyesight.