1, the food supply is seriously insufficient, intake is insufficient, such as: food single, improper storage, cooking destruction. such as folic acid heat loss.
2, absorption and utilization decreased, such as: digestive diseases or too little fat intake to affect the absorption of lipid-soluble Vit.
3, vitamin needs relative increase, such as: Pregnant and lactating women, children, special types of work, special circumstances of the crowd.
4, unreasonable use of antibiotics will lead to increased demand for vitamins.