Vitamin B12

Facts & Recommendations

Vitamin B12 (also called Cobalamin) is, like folic acid, a water-soluble B-vitamin. This vitamin exists in several forms, the naturally occurring ones (methylcobalamin, adenosylcobalamin and hydroxycobalamin) and the synthetic one, cyanocobalamin.

All vitamin B12 forms have been shown in clinical studies to improve vitamin B12 status.


The main sources of vitamin B12 are of animal origin: fish, meat, liver and to a minor degree dairy products and eggs.

For all those on a vegetarian/vegan diet or who eat little meat, the supply with this vitamin may prove to be difficult.


The bioavailability of vitamin B12 in humans with normal gastro-intestinal function is estimated at 50% depending on the dietary source.


The water-soluble vitamin B9 is extremely sensitive to light.
Vitamin B12, bound to protein in food, is released by the activity of the gastric juices in the stomach and is absorbed mainly in the small intestine. Vitamin B12 can be stored in the liver and in the kidney.


Together with folic acid, vitamin B12 plays an important role for the synthesis of DNA as well as for the proper blood cell formation and neurological function. It is hence essential during pregnancy to support the growth of the developing foetus.

Furthermore, vitamin B12 in association with folic acid regulates the homocysteine level in blood (homocysteine is a naturally occurring amino-acid which at high concentration in blood is associated with cardiovascular disease).

Both vitamins, B12 and folic acid, are known to work together “hand in hand” and should be both available to the body at a sufficient level, especially before conception.

Vitamin 12 deficiency is common and rises with age (due to increased occurrence of atrophic gastritis or pernicious anaemia for example).

Pregnant women who are vegans and vegetarians, those with pernicious anaemia or malabsorption syndromes such as Crohn’s disease or coeliac disease are considered to be at greatest risk of deficiency.

What is pernicious anaemia?

Pernicious anaemia is an autoimmune disease that affects the gastric mucosa leading to failure to produce intrinsic factor, resulting in vitamin B12 malabsorption. If left untreated, it causes a vitamin B12 deficiency

Consequences of a vitamin B12 deficiency

A vitamin B12 deficiency include neurological changes, chronic tiredness, megaloblastic anaemia, digestive disorders and cardiovascular disease.

A deficiency in pregnant women is associated with placental-related complications, such as pre-eclampsia and foetal growth restriction, with neural tube defects (NTDs), an increased risk of preterm delivery as well as postnatal depression.


Several studies have shown that

  • Vitamin B12 is necessary for fertility in both men and women;
  • an adequate intake of vitamin B12 and folic acid before and during pregnancy is linked to a lessened risk of NTDs and other associated risks, mainly occurring during the first trimester.

The current recommendations for vitamin B12 daily supplementation during pregnancy and lactation range around 3 µg; however, scientists insist that these intake recommendations be re-evaluated. The German Federal Institute of Risk Assessment (BfR) has recently increased the highest vitamin B12 concentration to be used in dietary supplements from 9 µg (2004) to 25 µg (2018).

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