February 05, 2014

Vitamin B12

Vitamin B12 also called cobalamin, is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood.

Functions of Vitamin B12

  • Vitamin B12 is an especially important vitamin for maintaining healthy nerve cells, and it helps in the production of DNA and RNA, the body's genetic material. 
  • Vitamin B12 also works closely with vitamin B9, also called folate or folic acid, to help make red blood cells and to help iron work better in the body. 
  • Folate and B12 work together to produce S-adenosylmethionine (SAMe), a compound involved in immune function and mood.
  • Vitamins B12, B6, and B9 work together to control blood levels of the amino acid homocysteine. High levels of homocysteine are associated with heart disease.


  • Meat Sources - Organ meats are the richest dietary sources of vitamin B12, including organ meats such as liver, kidney, pancreas, and heart, Lean beef and lean meats such as poultry are also good sources.
  • Seafood Sources - Various types of seafood are good sources of cobalamin, particularly bivalve molluscs (shellfish) such as clams and oysters. Tuna is another good source.
  • Dairy Sources - All dairy foods, such as milk, milk products, cheeses, cottage cheese, and yogurt supply vitamin B12.
  • Fermented Soy Sources - Fermented soy products, such as miso also contain vitamin B12.
  • Cheese: Though not all types of cheese are high in vitamin B12, Swiss, Parmesan, Mozzarella and Feta cheeses all contain vitamin B12.
  • Milk and Yogurt: 100 grams of non-fat yogurt provides 0.53μg (10% DV) of vitamin B12 and 15%DV per cup. 100 grams of reduced fat milk provides 0.46μg (8% DV) and 19% DV per cup. 
  • Eggs: The raw yellow portion of a chicken egg contains large amounts of vitamin B12. Goose eggs and duck eggs also provide substantial amounts of vitamin B12.
  • Fortified foods: These include soyamilk, cereals, biscuits and cookies. 
  • Brewer's and nutritional yeasts: It does not contain B12 unless they are fortified with it. There is at least one vegan, B12-fortified yeast currently on the market: Red Star Vegetarian Support Formula.

Daily Recommendation

  • 19 years and older: 2.4 mcg (RDA)
  • Pregnant women: 2.6 mcg (RDA)
  • Breastfeeding women: 2.8 mcg (RDA)


  • A lack of vitamin B12 can lead to megloblastic anemia, which illustrates the connection between folate and vitamin B12. Pernicious anemia is a type of megaloblastic anemia that results from insufficient vitamin B12 intake or from deficient secretion of gastric intrinsic factor. Depending on the severity of the symptoms, neurologic disorders resulting from a cobalamin deficiency may or may not be able to be reversed through treatment. A deficiency can also disrupt the synthesis of DNA, which can negatively affect normal cellular growth and repair.
  • In elderly people, vitamin B12 deficiency may result in mental disorientation, memory loss, and a yellowish tint to the skin (jaundice).

Who are prone to deficiency

  • Vegans, vegetarians who also don't eat dairy or eggs 
  • People with problems absorbing nutrients, due to conditions such as Crohn' s disease, pancreatic disease, and people who have had weight loss surgery
  • People who are infected with Helicobacter pylori
  • People with an eating disorder
  • People with HIV


General symptoms of vitamin B12 deficiency can include tiredness, weakness, abdominal pain, nausea, constipation, flatulence, reduction in appetite, menstrual problems, pallor of skin, headache, fatigue, syncope, short breath, and palpitations. Neurological problems can also result from a vitamin B12 deficiency. These problems can include numbness or tingling sensations in the hands and feet, progressive neuropathy, weakness in the legs, and problems walking.


Vitamin B12 is generally safe and is not toxic even when ingested in very large doses through either food or vitamin supplementation.



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