[Assessment methods and evolution on vitamin A status].

Vitamin A is one of nutrients which are indispensable to all people, especially children and pregnant women. In the world, severe vitamin A deficiency (VAD) has been controlled efficiently. But to many countries, especially those developing, subclinical or marginal vitamin A deficiency is still a public health problem. It is very important and necessary to assess the status of vitamin A of the population who are in risk of VAD before drawing and carrying out the intervention strategy. Currently, clinical, histological, functional and biochemical methods can be used to evaluate the level of vitamin A.