Vitamin A: A Visionary Vitamin
Vitamin A is an essential component of the human diet. The vitamin is present in numerous foods, including liver and other animal meats, carrots, sweet potatoes, mangos, eggs and butter. Sometimes it is absorbed as a vitamin, and sometimes it is absorbed as a provitamin and must be converted by the body. This vitamin is stored in the liver, and is necessary for the proper functioning of many parts of the body, from the immune system to the eyes and everything in-between. However, like many minerals and supplements, vitamin A can be toxic if taken in exorbitant doses.
The Good
Vitamin A is one of the most essential factors in good eyesight. From pigments to the cornea itself, the vitamin influences how well a person sees, what they see and when they see it. The vitamin aids in the creation of rhodopsin, a pigment in the eye capable of producing night vision. It also protects the corner and retina from drying out.
Vitamin A also plays a role in the health of skin and mucous membranes, normal bone growth, tooth development and reproduction. It can also act as an antioxidant, reducing the risk of cancer. Many cosmetic and medical companies use the vitamin as acne treatments and anti-aging products.
The Bad
The manifestations of vitamin A deficiency are numerous, although one of the first signs is an increase in acne and reduced night vision. The most devastating affects of this deficiency occur in the eyes; the cornea can literally erode without the presence of sufficient vitamin A. Nearly 500,000 malnourished children in third-world countries go blind each year from lack of the vitamin. The deficiency can also result in a reduced immune system and as well as changes to the cells lining organs and air passages.
The Ugly
Because vitamin A is stored in the body, excess traces of the vitamin are hard to dispose of. The vitamin is toxic in large doses, and this toxicity can result in nausea, headaches, weakness, altered mental status, jaundice and blurry vision. In more serious cases of vitamin A toxicity, fever, weight loss, bone fractures, peeling skin and insomnia are present as well.
While the acute symptoms are uncomfortable, the long-term effects of a vitamin A overdose are devastating. Birth defects, hair loss, osteoporosis and liver disease are all possible when too much of the vitamin is ingested over a long period of time.
Some sources of vitamin A contain too much of the vitamin, and ingesting these products can result in an immediate overdose. One meal of polar bear liver can make a sled dog sick and can kill a person.
