Vitamin B12 is a member of the water-soluble B-vitamins. Vitamin B12 helps to regenerate folate coenzyme and since folate also helps to restore Vitamin B12, these vitamins are interrelated. Vitamin B12 helps to maintain nerve fibers and promote their normal growth. B12 also is involved in the production of red blood cells and assists in DNA synthesis and energy production. Since the body cannot produce B12, it must be consumed in the diet. Deficiency symptoms of inadequate B12 include anemia, fatigue, and nervous system degeneration progressing to paralysis. B12 is found almost exclusively in animal sources such as meat, cheese milk and eggs. There is little risk of toxicity when taken orally in amounts that exceed the recommended intake.
Many bodybuilders take injectable B12 to help increase their appetite and overall health. You can get similar benefits from taking sublingual B12, since it is readily absorbed into the bloodstream. Injectable B12 is usually veterinary quality and comes from underground sources. B12 is often injected into the muscle or subcutaneous fat, never into the bloodstream.