In the investigation in 2008, the proportion of subclinical vitamin A deficiency, defined as serum retinol concentration < 0.7 μmol / L, and low serum retional level, defined as serum retinol concentration in 0.7 - 1.05 μmol / L, are 3.5% and 30.8%; no clinical vitamin A deficiency is observed. In addition, approximately 30% lactating women are subclinical vitamin A deficiency.