Long-term Vitamin B12 deficiency can result in demyelination of large nerve trunks and the spinal cord, reduced white blood cells, and in pernicious anemia with symptoms of severe fatigue, shortness of breath, dizziness and headaches. Red blood cells become abnormally enlarged and reduced platelet formation causes poor clotting and bruising. While high intake of folic acid prevents the red blood cell changes caused by a Vitamin B12 deficiency, it does not prevent the resulting nerve damage, which may only become apparent in later stages and may not be reversible... Full Text