Vitamin B12: Tasks And Functions

Vitamin B12 is an important vitamin for the blood, heart, brain and nerves. The vitamin is also involved in detoxification. We explain what vitamin B12 is and present the tasks and functions of the vitamin.

Vitamin B12 is actually a group of vitamins

Vitamin B12 is an essential vitamin, which means the body cannot make the vitamin itself. Instead, it must be ingested with food. B12 is particularly found in animal foods, very rarely in plant foods.

The term “vitamin B12” is the name for a whole group of so-called cobalamins. This includes:

  • Adenosylcobalamin: Adenosylcobalamin is the active form of the vitamin and is also the most common form of B12 in the organs.
  • Methylcobalamin: Methylcobalamin is another active form of the vitamin and, along with hydroxocobalamin, is the most common form of B12 in the blood.
  • Hydroxocobalamin: Hydroxocobalamin is the B12 storage form, which makes up about half of the vitamin B12 found in the blood, but is also found in many foods. On the one hand, hydroxocobalamin has to be converted into one of the two active forms in three conversion steps, but it also has important tasks before conversion (e.g. in detoxification and in the elimination of nitrostress).
  • Cyanocobalamin: Cyanocobalamin is a synthetic form of cobalamin that does not occur naturally but is commonly used in vitamin supplements. Cyanocobalamin must first be converted into an active form in the body, can hardly be stored, is not very bioavailable and is therefore not very recommendable overall.
  • Analogues: Analogues are also called pseudo-vitamin B12. These are compounds that have a similar structure to vitamin B12 (without having its positive effects) and therefore block the transporter molecules of real B12 and thus inhibit the absorption of real B12. Analogues are therefore B12 forms that are not bioavailable and are therefore classified as harmful.

Vitamin B12: A product of microorganisms

Vitamin B12 is produced exclusively by certain microorganisms. Plants cannot make B12. If the vitamin is found in plants, it is because the corresponding microorganisms have settled on them.

Meat – especially meat from ruminants – only contains B12 because vitamin B12-producing microorganisms live in the animal’s stomach, and the vitamin B12 from these microorganisms is absorbed by the animal. Only now can it be distributed in the tissue and also in the milk.

The meat from other animals (which are therefore not ruminants) is therefore significantly poorer in vitamin B12, e.g. B. that of pigs or poultry.

Unicellular sea plants or algae (phytoplankton) live in close symbiosis with B12-producing bacteria. Therefore, when fish eat plankton, they also absorb the vitamin, which is why the flesh of fish (and other seafood) also contains B12.

The tasks and functions of vitamin B12

Vitamin B12 is an extremely important vitamin. It is involved in blood formation and cell formation, in energy metabolism and the body’s own detoxification; it also protects the cardiovascular system and is essential for the brain and nervous system. The most important tasks and functions of vitamin B12 include the following:

Cell division and DNA formation

Vitamin B12 (cobalamin) is involved in cell division and cell growth as well as in the formation of DNA (genetic material). Children with a deficiency therefore suffer from serious developmental disorders, which of course can also be the case during pregnancy if the mother-to-be has a deficiency. A B12 deficiency should therefore be avoided at all costs, especially during pregnancy, and a B12 deficiency in the mother is even said to be able to promote diabetes in the child.

Protection against blood vessel damage in diabetes

Since diabetics are particularly susceptible to blood vessel damage and a B12 deficiency promotes blood vessel damage, vitamin B12 is very important in diabetes. In addition, together with other B vitamins, it prevents nerve damage (polyneuropathy) that often occurs with diabetes. Conversely, a 2019 study found that diabetics with polyneuropathy very often have a B12 deficiency.

Therefore, if you are diabetic, get your vitamin B12 levels checked – especially if you are taking metformin, a diabetes drug known to cause vitamin B12 deficiency in diabetics.

Formation and regeneration of nerves

B12 is very important for the nervous system as it helps in the formation and regeneration of nerve fiber sheaths. Neurological disorders, such as the polyneuropathy described above, but also neuropsychiatric disorders are therefore among the symptoms of B12 deficiency. These can escalate to depression and dementia.

No wonder it was also found in a study published in January 2016 that people with autism and people with schizophrenia have extremely low B12 levels. The neuropsychiatric disorders can appear even before the anemia described below appears.

It should also be borne in mind that some neurological disorders are irreversible, i.e. they cannot regress after B12 intake if the B12 supply is too late.

Alzheimer’s Prevention

B12 deficiency causes older people’s brains to shrink, according to a 2008 study featured in our article on the importance of vitamin B12 for the brain. Another study (from 2012) showed that even a mild B12 deficiency can accelerate mental decline. In the case of dementia and Alzheimer’s, vitamin B12 is therefore always part of the therapy, especially of course if a deficiency has been determined after the value has been determined.

Helps with insomnia

In the case of insomnia, vitamin B12 can, together with other vitamins, significantly improve sleep. Because B12 is involved in the regulation of the sleep hormone melatonin and thus the sleep-wake cycle. It also calms the nerves. Studies have shown that sleep quality deteriorates as B12 levels fall. Since B6 also improves sleep quality and vitamin D deficiency can cause sleep disorders, these two vitamins should also be checked if poor sleep is plaguing you.

Breakdown of homocysteine

Together with vitamin B6 and folic acid, vitamin B12 breaks down toxic homocysteine ​​– which is naturally produced as part of protein metabolism – into a non-toxic substance. In the case of a B12 deficiency, homocysteine ​​cannot be broken down completely. The homocysteine ​​level in the blood is now rising and poses a serious threat to the blood vessels there. Homocysteine ​​damages the blood vessel walls, so that repair processes have to take place there, which in turn can lead to arteriosclerotic deposits. Therefore, high homocysteine ​​levels are considered a risk factor for cardiovascular disease.

Blood formation

Since vitamin B12 is also involved in blood formation, a B12 deficiency leads to a special form of anemia. It is the so-called pernicious anemia, which we explain in detail in our article on B12 deficiency and how to fix it.

In chronic inflammatory bowel disease

In the case of chronic inflammatory bowel diseases ( IBD ), vitamin deficiencies often occur, since on the one hand the inflamed intestinal mucosa has absorption problems and on the other hand vitamins are excreted faster than they can be absorbed due to chronic diarrhea. Vitamin B12 is also often deficient in IBD and should therefore be supplemented together with other vitamins and minerals in order to avoid serious consequences of the corresponding deficiencies.

Vitamin B12 deficiency more common than previously thought

In 2018, Irish researchers showed that vitamin B12 deficiency is more widespread than previously thought. In their corresponding study, they wrote that not only is B12 deficiency widespread (every 8th person over 50), but at the same time often also a folic acid deficiency (every 7th person over 50).

In Germany, the situation is sometimes even worse: Here, up to 25 percent of men and up to 50 percent of women are affected by a B12 deficiency.

Vitamin B12 deficiency due to acid blockers

Last but not least, vitamin B12 deficiency is so widespread because the deficiency can develop as a result of acid blockers – and acid blockers are taken by many people over long periods of time. Acid blockers block the production of acid in the stomach lining cells. However, these cells not only make the stomach acid, but also the intrinsic factor, which is required for the absorption of B12 but is now missing due to the stomach drugs.

Vitamin B12 deficiency especially in the elderly

Older people in particular suffer from vitamin deficiencies. The reason for this is quickly explained. The 50+ population often takes medications (such as acid blockers or metformin (antidiabetes medication) or both) that promote B12 deficiency. Antibiotics, cortisone, psychotropic drugs and many others also affect the stomach, disrupt digestion and worsen the absorption of vitamins.

Vitamin B12 deficiency – consequences and symptoms

The possible symptoms and consequences of a vitamin B12 deficiency can already be estimated from the above tasks and functions of vitamin B12. These are not to be taken lightly.

Identify vitamin B12 deficiency

A vitamin B12 deficiency can be diagnosed by any family doctor without any problems. There are now also home tests that can be ordered online and can be used to determine a vitamin B12 deficiency in the urine.

Vitamin B12 in food

Most vitamins can be easily absorbed through certain foods. With vitamin B12 this is not so easy. Because the vitamin is almost exclusively found in animal foods, which for many people are no longer an option for ecological and ethical reasons.

Vegan vitamin B12: soy, tempeh, sea buckthorn

By “vegan vitamin B12” is meant B12 in plant foods, e.g. B. in soy, tempeh or sea buckthorn. In our article about soy, we clarify whether the vitamin is contained in soy products or whether soy products – as is sometimes claimed – can even increase a B12 deficiency. For example, tempeh is a fermented soy product that has long been considered a good source of B12.

Vitamin B12 during pregnancy and lactation

Since vitamin B12, as mentioned at the beginning, is involved in blood formation, cell division, cell growth and the formation of genetic material, you should pay very close attention to a good B12 supply during pregnancy and breastfeeding. Otherwise, there may be developmental disorders in the infant and, in extreme cases, permanent neurological or psychological damage.

Breastfeeding women provide their infant with sufficient vitamin B12 through breast milk – provided they are well supplied with the vitamin themselves. A B12 supplement that is combined with folic acid, e.g. B. the preparation vitamin B12 + active folic acid from effective nature, which provides 1000 µg B12 and 400 µg folic acid per daily dose.


Vitamin B12 is often offered in high-dose preparations. The mainstream media therefore repeatedly warns against overdosing.

Side effects

As you read in the above article on B12 overdose (which is almost impossible), there is no maximum limit for the vitamin – simply because there is no known toxic effect. Nevertheless, nutrition experts warned in a TV documentary about possible side effects of vitamin B12 and claimed that high doses of vitamin B12 could increase the risk of bone fractures and lung cancer.

Fix vitamin B12 deficiency

So while B12 overdose is rare, vitamin B12 deficiency is much more common. It is often said that this mainly affects vegan people. That’s not true. We now know that a B12 deficiency also often occurs in people who eat meat etc. regularly. In our article Resolving a vitamin B12 deficiency, we explain how you can identify a B12 deficiency, how to interpret the values ​​correctly and which B12 preparations are available to correct the deficiency.

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