Judy He

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. 

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