<P> Iodised salt has been used in the United States since before World War II . It was discovered in 1821 that goiters could be treated by the use of iodized salts . However, it was not until 1916 that the use of iodized salts could be tested in a research trial as a preventative measure against goiters . By 1924, it became readily available in the US . Currently in Canada and the US, the RDA for iodine is as low as 90 μg / day for children (4--8 years) and as high as 290 μg / day for breast - feeding mothers . </P> <P> Diseases that are associated with an iodine deficiency include: mental retardation, hypothyroidism, and goiter . There is also a risk of various other growth and developmental abnormalities . </P> <P> Folic acid (also known as folate) functions in reducing blood homocysteine levels, forming red blood cells, proper growth and division of cells, and preventing neural tube defects (NTDs). In many industrialized countries, the addition of folic acid to flour has prevented a significant number of NTDs in infants . Two common types of NTDs, spina bifida and anencephaly, affect approximately 2500 - 3000 infants born in the US annually . Research trials have shown the ability to reduce the incidence of NTDs by supplementing pregnant mothers with folic acid by 72% . </P> <P> The RDA for folic acid ranges from as low as 150 μg / day for children aged 1--3 years old, to 400 μg / day for males and females over the age of 19, and 600 μg / day during pregnancy . Diseases associated with folic acid deficiency include: megaloblastic or macrocytic anemia, cardiovascular disease, certain types of cancer, and NTDs in infants . </P>

1. give 2 examples and describe the process of vitamins enrichment in food