Vitamin B12 deficiency is most commonly caused by a lack of intrinsic factor - a substance produced in the stomach that is necessary for the absorption of vitamin B12 from food. When intrinsic factor is lacking, vitamin B12 is unable to be absorbed and is therefore unable to be utilised by the body. Pernicious anaemia is one such condition where the production of intrinsic factor is impaired. It is a leading cause of vitamin B12 deficiency. Other causes of vitamin B12 deficiency include:
- A diet inadequate in vitamin B12 rich foods - particularly so in vegetarians who don’t eat any animal products, meat, fish, milk, eggs, butter, cheese and other dairy products (vegans)
- Inadequate absorption or utilisation of B12 because of gastric abnormalities such as coeliac disease, inflammation of the stomach (gastritis), or pancreatic insufficiency
- Inadequate absorption can also occur after stomach and intestinal surgery as well as in inflammatory bowel diseases like Crohn's disease
- An increase in certain intestinal organisms
- Drugs that may interfere with the absorption of vitamin B12
- Heavy alcohol consumption
- Rare congenital disorders.
Symptoms of vitamin B12 deficiency usually don’t appear for at least two years. The reason for this is that a large amount of vitamin B12 is usually stored by the liver. Most people, apart from vegans, have a three to five year supply in their bodies. Initial symptoms of vitamin B12 deficiency can include:
- Shortness of breath
- Hearing difficulties.
If left untreated vitamin B12 deficiency can cause progressive damage to the nervous system, especially the nerves outside the brain and spinal cord. When the spinal cord is involved, the first symptoms include difficulty in feeling vibrations in the feet, loss of position sense, and loss of muscle co-ordination (ataxia). Other symptoms of untreated vitamin B12 deficiency may include:
- Weight loss
- An enlarged spleen and liver (hepatosplenomegaly)
- Exaggerated reflexes
- Mild depression and confusion
- Hallucinations, personality and mood changes
- Damage to the optic nerve.
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McGill University Health Centre (2012). Vitamin B12 Deficiency; tracking the genetic causes (Web Page). https://muhc.ca/newsroom/news/vitamin-b12-deficiency-tracking-genetic-cause . [Accessed: 14/09/16]
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Turner, J. (2005) Vitamin B12. The Gale Encyclopedia of Alternative Medicine. 2nd Edition. Jacqueline L. Longe, Editor. Farmington Hills, MI: Gale Group.
University of Otago and Ministry of Health. 2011. A Focus on Nutrition: Key findings of the 2008/09 New Zealand Adult Nutrition Survey. Chapter 4. Nutrient intakes and dietary sources: Micronutrients. Wellington: Ministry of Health. http://www.health.govt.nz/system/files/documents/publications/a-focus-on-nutrition-ch4_0.pdf
Last Reviewed – September 2016