Supplementing the diet with folic acid and vitamin B lowers plasma homocysteine. Tatsoi contains high levels of vitamin C, carotenoids, folic acid, calcium and potassium. There are concerns that large amounts of supplemental folic acid can hide vitamin B deficiency. Within the field of organic chemistry, folate refers to the conjugate base of folic acid. This risk can be reduced with folic acid supplementation before pregnancy. Prenatal supplementation with folic acid did not appear to reduce the risk of preterm births. Other risk factors include diets low in protein, folic acid, and carotene. Dietary supplementation of folic acid had been previously recommended by the WHO. Preconceptional intake of folic acid is recommended to reduce birth defects. Folic acid supplements have little established role in cancer chemotherapy. There is also a variation by strain for requirements of riboflavin, pyridoxal and folic acid. Adequate intake of folic acid, and iron is often recommended. Blackberries are also noted for containing manganese and folic acid. Mood stabilizers and anticonvulsants may interfere with folic acid absorption and L-methylfolate formation. Over 80 countries require folic acid fortification in some foods.