Vitamin A: Nutrition or Poison

When talking about vitamin A, the first thing we mention probably is the relevant deficiency disease. But recently, experts begin to worry that whether too much amount of this vitamin will become a poison. Scientific results tell us that ordinary diet will not lead to it.

When

talking about vitamin A, the first thing we mention probably is the relevant deficiency disease. But recently, experts

begin to worry that whether too much amount of this vitamin will become a

poison. Scientific results tell us that ordinary diet will not lead to it.



Lacking of vitamin A is one of the four deficiency

diseases in the world. This vitamin is a necessary organic compound for normal

vital activities. Its amount in the human body is quite tiny. But it plays a

very important role in metabolism and growth.

There are

four functions of this type of vitamin. The first is to maintain the

integrality of mucous layer. Or it will lead to keratosis. The second function is to compose the photoactive substances in

the visual cells. Otherwise, the adaptation of the eyes would be worse. And

sometimes patients would even suffer from nyctotphlosis.

Another function is to promote the growth and procreation. And the last is to

improve immunity.

 Lacking

of vitamin A in the world can lead to a death of one million to 2.5 million. A

half million children under the school age would become blind every year

because of this reason. A four-month-long investigation about it in China revealed that 11.7% of children in China lacked

this vitamin. This problem in China,

especially the western China,

is quite severe. In developed countries, clinical cases are much fewer but the

situation is also worrying. 

However,

we should keep in mind that vitamin is water-soluble or fat-soluble. When there

is too much in the human body, the water-soluble vitamin will not affect the

body but the fat-soluble vitamin will be stored in the fat and become a

poison.  Vitamin A belongs to the

fat-soluble type, storing in the liver. Excessive vitamin A can cause

poisoning.  

Usual

diet and nutrient fortified food

generally would not lead to poisoning. Almost all the poisoning is eating too

much by accident. As early as the 1590s, pathfinders in the arctic pole ate the

liver of polar bears, which contained a large amount of vitamin A, had the

symptoms o headache, vomit and somnolence. Once a 19-year-old man ate

half a kilo of dog livers and was poisoned by vitamin A. Later, he was advised

not to livers for half a year. Too much amount will destroy the cells and

bones. So if excessive vitamin A is ingested by pregnant women, it will even

lead to congenital malformation.