Water soluble vitamins and health - Vitamin B12

24 important questions on Water soluble vitamins and health - Vitamin B12

Which group of compounds is vitamin B12?

The name vitamin B12 is generic for a specific group of cobalt-containing corrinoids with biological activity in humans.

What is a source of vitamin B12?

Vitamin B12 is produced by bacteria.

How is Vitamin B12 present in foods?

in the free form and bound to proteins.
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How is protein bound vitamin B12 released?

Trough acidificationin in the stomach and enzymatic degratation of the protein (especially by pepsin).

What kind of condition in the stomach can impair vitamin B12 uptake?

Impaired gastric acidification, as in achlorhydria or with chronic use of antacids.

How does absorption of g-complex bound vitamin B12 go?

  • Trypsin (created in the pancreas) releases the vitamin B12 in the upper small intestint.
  • Her it can bind to a protein that is produced it the stomach. This protein is called intrinsic factor.
  • Now it goes to the ileum (lower part of small intestine) and the B12- Intrinsic factor-complex attaches to specific receptors present ont the intestinal cells.
  • These cells facilitate absorption.

What happens to vitamijn B12 in the intestinal cells?

Vitamin B12 is bound to transcobalamin II, a specific binding protein that carries vitamin B12 through the bloodstream.

How does cellular uptake of the target organs occur?

Cellular uptake occurs through a receptor-mediated process that recognizes the transcobalamin II protein.

What kind of relationship do the liver and the vitamin B12 have?

  • The liver converts vitamin B12 into its active coenzyme forms.
  • The liver also stores 60 % of all the body’s vitamin B12.

What is entherophatic circulation?

This is the process in which something (like vitamin B12) is excreted trough the bile but comes back in the liver after absorption.

Why is vitamin B12 necessary?

For the formation of blood cells, nerve sheaths and various proteins
And thereby it's essential for the prevention of megaloblastic anemia and neurological disturbances.

It is also a co factor in fat and carbohydrate metabolism and is essential for growth becasue the fat and carbohydrates are converted into cellular components.

What is megaloblastic anemia?

Megaloblastic anemia is a condition characterized by the release into the blood of immature red blood cells.This is because of failure of the normal process of maturation in the bone marrow.

What is pernicious anemia?

The combination of anemia with neurological problems (caused by vitamin B12 deficiency)

What is methionine synthase?

It is the enzyme that recycles hormocysteine back to methionine.
They are involved in the produciton of the active form of folate. So therfore low B12 may lead do distrubance of folate metabolsim
B12 is the co factor of  methionine synthase

What does methylmalonyl CoA mutase?

  • It converts methylmalonyl CoA into succinyl CoA.
  • This is an important reaction needed to produce energy from proteins and fats.
  • Succinyl-CoA is also required for the production of hemoglobin, the protein responsible for transporting oxygen in the blood. 

What does the nameless enzyme do?

It changes 3D structure of the amino acid leucin.
It needed this to maintain the myelin sheath that surrounds nerve cells

What can a lack of B12 do the DNA synthesis?

Lack of B12 leads to defective DNA synthesis in cells, which influences the growth and repair of all cells.


Tissues most affected are those with the greatest rate of cell turnover, for example the bone marrow that is involved in the production of blood.

What can a lack of vitamin B12 do with homocysteine?

Vitamin B12 deficiency can also lead to increased levels of homocysteine, which is a possible risk factor for vascular disease.

What is the difference between B12 and folate deficiency?

Symptoms are almost the same but the major difference is that only a lack of B12 is associated with neurological disturbances.


If folic acid is used to treat a B12 deficiency, the anemia may be cured but the risk of damage to the nervous system remains.

If left untreated nerve problems associated with a lack of B12 can be irreversible and potentially life threatening.

Why are more older people suffering form a B12 deficiency?

Because they have a decreased secretion of hydrochloric acid in there stomach and it promotes bacterial overgrowth.
As a result, these people are not able to release the B12 that is present in food, and the amount of available B12 is further reduced due to consumption by the bacteria.

How can a autoimmune disease cause B12 deficiency?

  • Without intrinsic factor, absorption of vitamin B12 is not possible.

  • Intrinsic factor is produced in the stomach by specific cells, and these cells can be destroyed by the immune system in people suffering from an auto-immune disease.
  • This often happens in people that have atrophic gastritis.

Which people are at riks of a B12 deficiency?

  • People with a malabsorption.
  • Older adults
  • Individuals with stomach and small intestinal disorders, (might not absorb enough)
  • People who had gastrointestinal surgery. (might not absorb enough it often result in a loss of cells that secrete hydrochloric acid and intrinsic factor. Reduced levels of hydrochloric acid and intrinsic factor lower the amount of vitamin B12, particularly food-bound vitamin B12, that is released and absorbed)
  • Surgical removal of the distal ileum can also result in the inability to absorb vitamin B12.
  • Vegetarians
  • pregnant and lactating woman with vegetarian diet (the infants of these woman to)

What is the upper limet of B12?

There is no upper limit.

What is the main form of B12 used in suplements?

cyanocabalamin body quickly converts it to B12

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