At a glance
Vitamin B12 (cobalamin) is a water-soluble B vitamin for blood formation, the nervous system and homocysteine metabolism.
In Vykea: methylcobalamin (960 µg per sachet in Omnia All-In-One)
Usable B12 is found almost exclusively in animal foods and deserves particular attention with a vegan diet.

Vitamin B12 is a water-soluble B vitamin. The collective term cobalamin covers several related compounds whose molecule contains a central cobalt atom. Vitamin B12 is involved in the formation of red blood cells, the function of the nervous system, the breakdown of homocysteine and cell division. A special feature among the vitamins: it occurs in significant amounts almost exclusively in animal foods, which is why it deserves particular attention with a purely plant-based diet. In Omnia All-In-One we use methylcobalamin, an already active coenzyme form of vitamin B12, at 960 µg per sachet. This entry explains the forms, food sources, functions, requirements, laboratory testing, possible signs of deficiency and interactions of vitamin B12.

The term vitamin B12 covers several cobalamins that differ in the group attached to the cobalt atom. In human metabolism, two of them are directly active as coenzymes: methylcobalamin, which is needed in the aqueous compartment of the cell and in homocysteine metabolism, and adenosylcobalamin (5-deoxyadenosylcobalamin), which acts in the mitochondria. Both are therefore regarded as the body's own active forms.

Four forms are mainly used in food supplements. Cyanocobalamin is the synthetic, particularly stable and inexpensive standard form; it does not occur in living organisms and must first be converted into an active form in the body, during which a small cyanide group is split off. Hydroxocobalamin is a naturally occurring storage and transport form with good tissue binding, which is often used in medicine as an injection. Methylcobalamin and adenosylcobalamin are the already active coenzyme forms.

Methylcobalamin does not need to go through the preceding conversion step that is necessary for cyanocobalamin and is directly available as a usable coenzyme form. Omnia uses methylcobalamin.

The absorption of vitamin B12 is regulated in a particularly complex way in the body. In the stomach, cobalamin taken in with food is released from its protein bonds and initially bound to a salivary protein (haptocorrin). In the small intestine, it then binds to intrinsic factor, a glycoprotein produced by the parietal cells of the stomach lining. Only this complex of vitamin B12 and intrinsic factor is absorbed in the lower small intestine (ileum) via special receptors. If this mechanism is impaired, for example with chronic gastritis or after surgery on the stomach or small intestine, absorption can be severely restricted.

Vitamin B12 is produced exclusively by certain microorganisms and enters the food chain via animals. It is therefore only found in significant amounts in animal foods. Good sources are offal such as liver, muscle meat, fish and seafood, eggs, and milk and dairy products. Particularly high levels are found in liver and in some types of fish such as herring and mackerel.

Plant foods generally contain no usable vitamin B12. Small amounts or cobalamin-like substances may occur in some fermented products, in algae or through bacterial contamination, but these are not regarded as a reliable or available source for humans. People on a vegan diet cannot reliably cover their requirement from unfortified plant foods alone (see the separate section).

Vitamin B12 is comparatively stable to heat, but some can be lost through prolonged cooking, through light and in acidic or alkaline conditions.

The two active forms act as coenzymes in two key metabolic pathways:

The section "Authorised health claims" further below shows which of these functions are authorised as health claims.

Vitamin B12 does not act on its own in metabolism, but works closely with two other B vitamins. In homocysteine metabolism, vitamin B12, folate and vitamin B6 form a coordinated trio: folate and vitamin B12 work together in the conversion of homocysteine to methionine, while vitamin B6 is involved in another breakdown pathway for homocysteine. If one of these vitamins is lacking, the homocysteine level in the blood can rise.

The link between vitamin B12 and folate is particularly close, because both come together in a single enzyme reaction. Methionine synthase transfers a methyl group from 5-methyltetrahydrofolate, the active form of folate, to homocysteine, thereby producing methionine. Vitamin B12, as a cofactor, is the direct carrier of this methyl group. According to current understanding, this is the only metabolic step in which folate and vitamin B12 are needed in the same reaction.

This shared reaction gives rise to a phenomenon described in the specialist literature as the methyl trap (also known as the methyl-folate trap). If too little vitamin B12 is available, methionine synthase stalls. Folate then remains trapped in the form of 5-methyltetrahydrofolate, as without the B12-dependent step it can neither be processed further nor converted back into its other active forms. As a result, even when there is enough folate on paper, the body cannot use it properly to form genetic material. This mechanism explains why vitamin B12 deficiency can lead to anaemia with enlarged red blood cells that resembles the anaemia seen with folate deficiency, and why the two vitamins are always considered together in metabolism. These are general relationships from nutritional science.

The following health claims are authorised for vitamin B12 in the EU:

These claims apply to vitamin B12 in general and therefore also to the form used in Omnia, methylcobalamin.

For vitamin B12, the German Nutrition Society (DGE) gives estimated values for an adequate intake rather than a recommended intake. The following values are taken from the D-A-CH reference values revised in 2018 and are given in micrograms of vitamin B12 per day. In that revision, the estimated value for adults was raised from 3.0 µg to 4.0 µg.

The nutrient reference value for labelling (NRV) is 2.5 µg per day. The European Food Safety Authority (EFSA) has not set a tolerable upper intake level for vitamin B12, as the available data did not provide a sufficient basis for a numerical value. Because it is water-soluble and its absorption via intrinsic factor is tightly regulated, vitamin B12 is regarded as well tolerated even at high intakes; any excess is mainly excreted via the kidneys.

Increased requirements or poorer status can occur in several situations. Because absorption via the gastrointestinal tract is regulated in a complex way, disorders of this pathway play a particular role: reduced stomach acid production, chronic gastritis, a lack of intrinsic factor, surgery on the stomach or small intestine, chronic inflammatory bowel disease, pancreatic insufficiency and bacterial overgrowth in the small intestine. Older people, whose stomach acid production often declines, are also more frequently affected.

In addition, pregnancy and breastfeeding, regular alcohol consumption, smoking and certain medicines can increase requirements or impair absorption (see the Interactions section). Diet plays a special role: people who follow a vegan or largely vegetarian diet obtain hardly any usable vitamin B12 from food.

Because usable vitamin B12 occurs practically only in animal foods, supply on a purely plant-based diet is the most important special case. Unfortified plant foods are not a reliable source. Scientific reviews consistently describe that inadequate supply is more common in vegans than in people on a mixed diet and in vegetarians, and that adequate status can generally be achieved through fortified foods or a supplement.

The DGE classifies vitamin B12 as the most critical vitamin in a vegan diet and explicitly recommends that vegans obtain it permanently via a supplement or fortified foods and have their status checked regularly by a doctor. Because the body can store vitamin B12 for years, a deficiency often only develops after a long time and can go unnoticed for a long period. Pregnant and breastfeeding women on a vegan diet should be particularly attentive, as the child is also supplied via the placenta and breast milk.

Note: A vegan diet during pregnancy and breastfeeding should be supervised by a doctor. The specific form, dosage and monitoring of intake should be left to a doctor.

Vitamin B12 status is determined by a doctor from a blood sample. Measuring total vitamin B12 in serum alone (reference range approximately 200 to 1,000 ng/l) is considered not very sensitive, as it also includes the fractions bound to haptocorrin, which are not available to the cells. Additional markers are therefore more informative.

Holotranscobalamin (holo-TC, also called active B12) is regarded as an early marker; it reflects the fraction directly available to the cells and already falls when stores are beginning to be depleted. Methylmalonic acid (MMA) and homocysteine in the blood serve as functional markers; both rise when too little vitamin B12 is available at metabolic level. A low holo-TC together with elevated MMA and elevated homocysteine indicates a deficiency that is having an effect at metabolic level, which may still be present without symptoms. There is no single, generally recognised gold-standard test; the markers are assessed together.

Note: Interpreting the values and any supplementation should be left to a doctor.

Because of the body's large stores, vitamin B12 deficiency usually develops slowly, often over months to years. The signs are initially non-specific and can have many causes. Tiredness, weakness, pallor, dizziness and shortness of breath have been described. Because vitamin B12 is necessary for blood formation, a longer-lasting deficiency can lead to anaemia with enlarged red blood cells (macrocytic or megaloblastic anaemia). Changes in the mucous membranes, such as an inflamed, reddened tongue, and gastrointestinal complaints are also possible.

A special feature of vitamin B12 is that a deficiency can affect the nervous system. The specialist literature describes abnormal sensations such as tingling and numbness in the hands and feet, unsteady gait, and memory and concentration problems. Such neurological symptoms can occur before changes appear in the blood count.

These signs are not conclusive and can have many causes.

Note: A suspected vitamin B12 deficiency, particularly with neurological symptoms, requires a medical diagnosis and cannot be replaced by self-treatment. Investigation and diagnosis should be left to a doctor.

Various medicines can lower vitamin B12 status or impair its absorption. Because vitamin B12 requires stomach acid and intrinsic factor for its absorption, medicines that reduce stomach acid can lower its availability; these include proton pump inhibitors and H2 receptor blockers. The diabetes medicine metformin can impair absorption in the gut and increase requirements when taken over a long period. Non-steroidal painkillers and oral contraceptives are also associated in the literature with an unfavourable effect on vitamin B12 status.

Note: If you take such medicines over a long period, you should check with a doctor beforehand about additional vitamin B12 intake and, if necessary, a check of your status.

In metabolism, vitamin B12 works closely with other B vitamins. Together with folate and vitamin B6, it is involved in the breakdown of homocysteine, and it shares a common metabolic pathway with folate in the formation of genetic material.

Folate and vitamin B12 are closely linked in metabolism, which has an important consequence for diagnosis. In megaloblastic anaemia caused by vitamin B12 deficiency, a high-dose intake of folate alone can improve the blood count and thus conceal an existing vitamin B12 deficiency (known as masking). The underlying damage to the nervous system can progress unnoticed. For this reason, vitamin B12 status should be clarified before taking high-dose folate, and the two vitamins are considered together in metabolism.

Note: Investigation and any supplementation should be left to a doctor.

Methylcobalamin is one of the two coenzyme forms of vitamin B12 that are directly active in the body. It is needed in homocysteine metabolism as a cofactor of methionine synthase and does not need to go through the preceding conversion step that is necessary for the synthetic standard form cyanocobalamin. In Omnia, vitamin B12 is present as methylcobalamin and is combined with folate, vitamin B6 and vitamin B2, with which it works together in homocysteine metabolism and one-carbon metabolism.

Note: Targeted or higher-dose use of vitamin B12, for example for a confirmed deficiency, should be left to a doctor.

Vitamin B12 is contained in Omnia All-In-One:

The amount stated refers to the vitamin B12 content. The % of NRV is based on the labelling value of 2.5 µg. The high calculated % of NRV results from the low labelling value and the special absorption via intrinsic factor, which limits the amount actually absorbed; vitamin B12 is regarded as well tolerated. In Omnia, vitamin B12 is combined with folate, vitamin B6 and vitamin B2, with which it works together in homocysteine metabolism. One daily dose corresponds to one sachet.

Food supplements are not a substitute for a balanced, varied diet and a healthy lifestyle.

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