Medical use of vitamin B9 is primarily for the treatment of folic acid deficiency and certain types of anemia (lack of red blood cells). Together with vitamins B6 and B12, it has been shown to reduce the risk of age-related macular degeneration. Folic acid together with cyancobalamine reduces blood homocysteine concentrations. Folate is critical for nucleotide synthesis, and intake of dietary folic acid is credited with reduced incidences of neural tube defects in infants. Several case-control studies have shown that folate may protect against neoplasia in ulcerative colitis.