叶酸
"Folic acid fortification" is a process where synthetic folic acid is added to wheat flour or other foods with the intention of promoting public health through increasing blood folate levels in the populace. It is used as it is more stable during processing and storage. After the discovery of the link between insufficient folic acid and neural tube defects, governments and health organizations worldwide made recommendations concerning folic acid supplementation for women intending to become pregnant. Because the neural tube closes in the first four weeks of gestation, often before many women even know they are pregnant, many countries in time decided to implement mandatory food fortification programs. A meta-analysis of global birth prevalence of spina bifida showed that when mandatory fortification was compared to countries with voluntary fortification or no fortification program, there was a 30% reduction in live births with spina bifida, with some countries reporting a greater than 50% reduction.