Vitamin B12 (Cobalamin)


Vitamin B12 (Cobalamin)

Vitamin B12 Uses Vitamin B12 (Cobalamin) can only be produced by microorganisms and as a result of its huge importance for good health, it is commonly used more and more today as a therapeutic agent. Vitamin B12 has an effect on almost all areas of our health. As an important coenzyme, it is required for the metabolism […]

Vitamin B12 Uses

Vitamin B12 (Cobalamin) can only be produced by microorganisms and as a result of its huge importance for good health, it is commonly used more and more today as a therapeutic agent. Vitamin B12 has an effect on almost all areas of our health. As an important coenzyme, it is required for the metabolism of cell reproduction and particularly concerns the formation of blood, protection of the nervous system, cell division, DNA synthesis, production of neurotransmitters, production of energy and protein metabolism. 

The importance of vitamin B12 today is increasingly apparent, especially for the nerves, balance of energy and mental health, which is why it is used in the treatment of numerous diseases.

Vitamin B12 Deficiency

The body relies on a daily supply of vitamin B12 in order to stay healthy. However, vitamin B12 can be stored in the liver, which is why it is not always necessary to ingest it daily in the diet.

Despite its storage capability, a  vitamin B12 deficiency is surprisingly common. The most common reason for this relates to vitamin B12 malabsorption. A vitamin B12 deficiency arises relatively quickly through dysfunction of the gastric and/or intestinal mucosa, but also from other causes such as the intake of certain medication that impedes B12 absorption. 

In some cases, not enough vitamin B12 is obtained. Vitamin B12 can be found almost exclusively in animal food sources. It is not uncommon that a seemingly healthy diet can completely lack an adequate vitamin B12 content. This is of particular relevance for vegetarians and vegans, for whom there is little feasibility of obtaining an adequate B12 supply from herbal sources. 

A deficiency in vitamin B12 can cause a variety of serious symptoms and secondary conditions that are unfortunately still not always quickly and positively identified. 

What is Vitamin B12?

Vitamin B12 belongs to the cobalamins category. This name derives from the positively charged cobalt ion. The cobalamins are the only known substances to naturally contain cobalt. Vitamin B12 is often thus treated as synonymous with cobalamin. It is an odorless, intensely dark-red colored, crystallized substance that is heat and light sensitive. 

Vitamin B12 is produced by microorganisms that are found living in the ground and in a few algae, but mainly in the body of humans and animals. In ruminants, the B12 bacteria cultivates in the paunch and a supplementary intake from an outside source is not necessary. Other herbivores ingest small amounts of B12 from scraps of earth and droppings in their food, in which these microorganisms live. For humans, a bodily vitamin B12 production from intestinal bacteria is actually theoretically possible, yet rarely achieved due to health reasons; which is why the human body today is dependent on a nutritional supply of vitamin B12 in almost all cases. 

Vitamin B12 Forms

Vitamin B12 exists in a variety of forms, where different molecules are combined with cobalamin. Microorganisms produce one of these, the so-called hydroxocobalamin, which can also be found in many foods. 

Hydroxocobalamin can be metabolized by the body into the bioactive coenzyme forms of methylcobalamin and adenosylcobalamin. Methylcobalamin functions within the cell plasma, whilst adenosylcobalamin (5′-Desoxyadenosylcobalamin) works in the mitochondria (the ‘engine room’ of the cell). 

Hydroxocobalamin and methylcobalamin are found in roughly equal measure in human blood. Adenosylcobalamin can be found in the body’s vitamin B12 store within the liver.

The latest addition to the cobalamin family is cyanocobalamin, a synthetic form which can be found today. Cyanocobalamin occurs only very rarely in nature as a detox product and is ineffective directly; it must first be converted by the body. 

Vitamin B12 Sources

Vitamin B12 naturally occurs exclusively in microorganisms that live in the ground and in the intestine. This vitamin B12 is predominantly found in high concentrations in giblets, meat, fish, cheese, egg yolks and milk (see table below). Additionally, it is also found in very small quantities via bacteria on the surface of fruits and vegetables. Unfortunately, it is no longer advisable to consume unwashed fruit and vegetables, unless they are homegrown. 

The body also regulates similar vitamin B12-producing bacteria in the intestine. These are found primarily in the large intestine, however they can only be ingested in the small intestine. Because of this, the majority of B12 produced by the body goes unused and is excreted through the stool.

Absorption of Vitamin B12 via the “Intrinsic Factor”

Intrinsic Factor Vitamin B12

Vitamin B12 digested through food is absorbed by a transport protein known as the intrinsic factor, which enables the intake of cobalamin through special receptors on the mucous membrane of the small intestine. The intrinsic factor is made up of parietal cells in the stomach lining. 

 Through the intrinsic factor, a maximum of 1.5 μg of vitamin B12 per meal/dose can be absorbed. A further 1% of the dose is absorbed through passive diffusion in the large intestine, meaning the total absorption is a combination of these two separate mechanisms.

With the body’s capability for B12 absorption explained, why do we often need to absorb large and regular quantities of this vitamin in order to meet our body’s relatively small demands? This is most common when the intrinsic factor is damaged through disease. 

 The liver is capable of storing relatively large amounts of vitamin B12 (around 2-5 mg). This is the body’s store for 50-90% of vitamins. In theory, this storage capacity can suffice for months and years. 

Causes of Vitamin B12 Deficiency

The following factors represent the main causes of a vitamin B12 deficiency:

  1. Dysfunction, irritation, inflammation or disease of the stomach lining (deficiency of the intrinsic factor) and/or lining of the small intestine (resorption), such as gastritis, Crohn’s disease, chronic enteritis, chronic diarrhoea and pancreatic disease. From this, the stomach lining becomes abnormal and will not produce enough of the transport protein the intrinsic factor, nor gastric acid. The usability of vitamin B12 is thereafter restricted or partially no longer possible. The same applies to a disorder or an inflammation of the mucous membrane of the small intestine. This can significantly reduce the absorption capabilities of cobalamin. People with a damaged or inflamed stomach or small intestinal lining can suffer from a serious vitamin B12 deficiency, despite their intake from food being typically sufficient. 
  2. Alcohol and drug consumption. The breakdown of alcohol and drugs requires a lot of vitamin B12 and more importantly strains the stomach lining and the liver. This can lead to poor development of the intrinsic factor and poor resorption in the intestine. 
  3. Diet of food not containing a high enough vitamin B12 content (most common in vegetarians and vegans) – malnutrition.  
  4. Increased vitamin B12 requirement caused by extenuating circumstances that haven’t been accounted for. This often results in chronic and nitrosative stress, caused by congestion, heavy metals, toxins, medication and traumas.

In addition to the above, the following can also cause a deficiency:

  • Worms / parasites. Tapeworms in particular consume large quantities of vitamin B12. A sufficient supply cannot be guaranteed whilst the worm remains in the body.
  • (Partial) excision of the stomach as a result of an operation.
  • Age. Often, seniors develop a weaker stomach wall. A vitamin B12 deficiency is usually the reason for tiredness, loss of memory and depressive mood amongst the elderly. 
  • Medication. Including contraception containing oestrogen and hormone supplements (proton pump inhibitors), diabetes medication (metformin), high blood pressure medicines (ACE), cardiac arrhythmia medication (beta blockers, nitrate sprays, nitroglycerin), cholesterol lowering medicines (statins) and impotence treatments.
  • Disease. liver disease (storage and transport problems).
  • A further aspect is that the initial symptoms of a vitamin B12 deficiency can also resemble those of extreme blood sugar level fluctuations (nervousness, extreme hunger attacks, difficulty concentrating, aggressiveness, irritability, sudden mood swings. It is important to think about other causes in these cases. Interestingly, vitamin B12 is also required for the metabolism of high levels of sugar (every type of isolated carbohydrate). This process also uses the trace elements manganese, chromium and zinc, along with the important mineral magnesium, which in turn has an indirect, negative effect on the B vitamins. This is because of their important roles in aiding the use of B vitamins: manganese, for example, aids the processes of vitamin B1. 

Vitamin B12 and Folic Acid

A significant amount of vitamin B12 is needed for the conversion of the important vitamin B9 (folic acid) into its usable form by the body. A lack of vitamin B12 results in a lack of active folic acid (folate). Vitamin B12 deficiency can then also trigger the symptoms of a folic acid deficiency, when actually there is sufficient folic acid, it just cannot be activated without the assistance of methylcobalamin. The symptoms of this are as follows:

  • Anemia, lethargy, tiredness, difficulty concentrating, difficulty forming blood cells, weakening of the immune system
  • Defection and inflammation of the stomach and intestine mucosa as well as the mouth, impaired nutrient absorption, diarrhea, loss of appetite, deuteropathy
  • Impaired development of fetuses, babies and children, birth defects
  • Irritation of the central nervous system, irritability, memory loss, anxiety, depression

Folic acid deficiency can also arise from stomach and intestinal diseases, pregnancy, malnutrition, medication and alcoholism.

Vitamin B12 Deficiency Symptoms and Consequences

A vitamin B12 deficiency can have serious and sometimes painful health consequences. It is essential for all transfers used in the metabolism and vital methyl group. This is relevant to the forming of nerve matter, the methylation of histamine or the recycling of homocysteine (risk factor for arteriosclerosis!), but B12 is also important for the metabolism of mitochondria (‘engine room’ of the cells). In addition to this, B12, together with folic acid, is vital to the formation of genetic material (DNA). The main vitamin B12 deficiency symptoms can be identified as follows. 

Nerve Disorders

Vitamin B12 is extremely important for the protection of nerve cells. A vitamin B12 deficiency corresponds most commonly with nerve health, such as demyelination of nerve fibers in the spinal cord. Typical symptoms include:

  • Nervousnous
  • Irritability
  • Feeling of numbness or a tingling of body parts, mostly peripherally but sometimes ranging up to strong pains in the extremities (hands, arms, feet or legs)
  • Tiredness
  • Neurological problems, such as a burning mouth syndrome (BMS, glossitis) 
  • Depression

It can occur that symptoms such as these are not immediately identified as a vitamin B12 deficiency. In one known case, an affected person was suffering from severe pains in the lower back and legs. The first diagnosis incorrectly suggested a slipped disc or a protrusion. It was only after a series of visits to the doctor and a blood count that a low vitamin B12 count was discovered. The patient then recalled a long history of stomach pains and general gastric trouble. 

Anemia and Lethargy

Vitamin B12 also plays an important role in the formation of red blood cells in bone marrow, which transports oxygen and nutrients in the blood to cells. Furthermore, it participates in the integration of iron into red blood cells. A decreased oxygen and nutrients intake leads to a general deficiency in the body, resulting in weakened immunity, tiredness and fatigue. This can lead to the development of a special form of anemia known as pernicious anemia, one of the larger family of megaloblastic anemias, a dangerous variety. 

Digestive Disorders

A third area of attention concerns the function of vitamin B12 in ensuring a good digestion and absorption capacity for nutrients. Digestive disorders caused by a lack of vitamin B12 can be revealed through:

  • Constipation
  • Diarrhea
  • Loss of appetite
  • Inflammation of the mouth, stomach and intestine
  • Weight loss
  • Yellowish skin tone

Impaired Vision

Vitamin B12 deficiency can lead to a slight visual deterioration and blind spots.

Vitamin B12 Deficiency: Test and Diagnosis

A vitamin B12 deficiency can be identified with the help of various vitamin B12 tests.

One way of gaining an early indication of a vitamin B12 deficiency is through a vitamin B12 urine test, which involves analysis of the methylmalonic acid concentration in the urine and is highly recommended. Numerous methylation processes in the body are damaged by a vitamin B12 deficiency. As a result, methylmalonic acid in the body is not sufficiently broken down and an increased amount of urine is excreted, which can be easily traced and identified in the urine. From this, it is possible to measure whether or not a functioning deficiency exists and whether the cells are receiving a sufficient level of B12 to function.

By contrast, a blood serum test cannot provide reliable information concerning a vitamin B12 deficiency, as the test cannot differentiate between genuine B12 and its dangerous, synthetic B12 analogs. However, it can be useful in strengthening the indication of a deficiency. A normal range for B12 blood levels is around 200-600 pg/ml.

A holotranscobalamin test (HoloTC) is even more reliable. In this, the actual transport molecules which cobalamin bonds to are examined. This is much more insightful because it focuses on the vitamin B12 which can be used by the body. 

By linking the findings and the causes, a deficiency can be determined. If enough vitamin B12 is being consumed through the diet, then a schilling test can help to determine whether the intrinsic factor effectively absorbs vitamin B12. Further examination of potential stomach and bowel diseases, reaction to medicine or other absorption problems can also be carried out. 

Daily Requirement: Vitamin B12 Guidelines

According to the National Institute of Health, a branch of the U.S. Department of Health and Services, the  RDA of vitamin B12 is as follows:

Empfohlene Tagesmenge Vitamin B12

Children & adults 14+2.4
Lactation & breastfeeding2.8
Children 9-13 years1.8
Children 4-8 years1.2
Children 1-3 years0.9
Babies 7-12 months0.5
Babies 0-6 months0.4

Note: These values vary. in Germany, the DGE gives their RDA as being 3 μg for adults, 3.5 μg during pregnancy and 4 μg during lactation. The EU daily requirement is listed as 2.5 μg for adults. Nutrition therapy can see doses from 10 μg per day, right up to 1,000 μg per day. 

These values have been calculated by vitamin B12 experts, but are considered almost unanimously to be too low a daily supply, given the vitamin’s complex absorption mechanism.

Foods Containing Vitamin B12

Since vitamin B12 is formed by microorganisms in the digestive system and on unwashed fruit and vegetables, sufficiently high levels are found principally in animal products. High B12 levels are also found in fatty seafood, meat and cheese. Vegetables, fruit, plant fats, pulses, grains and rice etc do not contain B12.

Vitamin B12 FoodsFisch VitaminB12

Cow’s liver




Calf’s liver




















Beef (lean)
















Eigelb Vitamin B12





Veal (lean)




Egg yolk (chicken)












Egg (chicken)








Pork (lean)




Cream cheese (at least 10% fat)




Quark (curds)




Cottage cheese








Sheep’s milk








Cow’s milk








Egg white (chicken)




Goat’s milk




Wheat beer




Gemüse Obst Vitamin B12





Plant fat or oil


(beans, chickpeas etc.)




Nuts and seeds


Cereals and wheat








Noodles and pasta






Beer (lager)




Source: Prof. Dr. Helmut Heseker, Dipl. oec. troph. Beate Heseker; Die Nährwerttabelle, 2. Aufl., 2012, Neuer Umschau Buchverlag, S. 22ff.

Vitamin B12 for Vegetarians and Vegans

Algen Vitamin B12

It is deducible that in earlier times, vegans procured sufficient vitamin B12 through an endogenous production of the vitamin, accompanied by consumption of unwashed fruit and vegetables and (unintentional) consumption of insects, maggots and worms. Since an endogenous production of vitamin B12 is only possible with excellent intestinal health, which cannot be achieved easily today as it is no longer advisable to eat unwashed fruit and vegetables, coupled with the fact that the body’s need for nutrients has increased greatly due to stress and disease nowadays, vegans cannot obtain sufficient nutrients from traditional foods. It is necessary instead to carefully plan a diet, especially with regard to B12 content. 

In naturopathic circles, the following foodstuffs are commonly listed as plant based vitamin B12 sources:

  • Foods fermented by lactic acid (with microorganisms), e.g. sauerkraut
  • Algae (in particular nori and chlorella)
  • Bacterially manufactured lupin products
  • Fermented soya products (miso, soy sauce or tempo)

These sources of vitamin B12 actually often contain so-called B12 analogs, which doesn’t have a positive, vitamin effect and can even hinder the absorption of real vitamin B12. Scientific studies on this matter often present some conflicting points of view. 

The foods above are also only considered healthy in moderation; they should not be consumed in excess because they are very difficult to digest. This is particularly relevant for those already suffering from stomach or intestinal problems. Because of this, B12 supply from the four categories stated above is limited. An additional point of note regarding algae is that they can sometimes be contaminated (particularly from heavy metals) and so checking the quality of the product and its purity before consuming is very important.

In many situations (such as increased stress, disease, etc), it would be sensible to take vitamin B12 supplements to replenish the body’s natural B12 store. The same is necessary not only for vegans but for vegetarians also, assuming they do not consume large measures of dairy products and egg yolks. Naturopaths suggest consumption of these foods in large quantities is ill-advised because it can be unhealthy (poor digestibility, high in fatty acids, mucous congestion from milk etc). For vegans and vegetarians, it is all the more important to ensure a sufficient vitamin B12 supply.

Vitamin B12 is Sensitive to HeatVitamin B12 (Cyanocobalamin) molecule

Tip: Vitamin B12 is sensitive to heat and its quality is noticeably reduced when cooked. For example, when milk is cooked for 20 minutes, its B12 content is reduced by around 30%. For this reason, foods containing vitamin B12 should not come into contact with high temperatures, or should at least be cooked for the minimum amount of time necessary. 

Vitamin B12 Supplements

When the diet cannot sufficiently cover the body’s vitamin B12 requirement, a vitamin B12 supplement can help. These supplements exist in many different forms. 

Vitamin B12 capsules, pills or drops and sprays are all available as oral supplements. The vitamin B12 here is absorbed either from digestion or by sublingual absorption through the oral mucosa in the case of lozenges, drop and sprays. Vitamin B12 toothpaste also uses sublingual absorption. 

To replenish the body’s B12 store or when absorption through the intestine is no longer viable, a B12 injection may be administered. With this method the digestive system is completely bypassed, allowing much higher doses of vitamin B12 to be absorbed so that the body store can be filled up quickly.

Today, high dosage oral supplements are considered equivalent to vitamin B12 injections because they can usually ensure enough B12 is absorbed via passive diffusion. 

Vitamin B12 Capsules and Pills

When taking vitamin B12 capsules, pills, drops or sprays orally, it is important to ensure that the product is as pure as possible, with little or no additives. From a naturopath viewpoint, the purer the supplement, the higher the bioavailability, effectiveness and tolerance. 

Vitamin B12 supplements most commonly contain methylcobalamin or cyanocobalamin as active ingredients, though hydroxocobalamin and adenosylcobalamin are also available too. Cyanocobalamin must first be activated by the body before it can be utilized. The majority of forums and contributors online recommend methylcobalamin, whilst the WHO prefers hydroxocobalamin. Adenosylcobalamin is also a popular choice amongst many Americans, although it is currently banned in certain countries in Europe. For an overview on the differences between the active ingredients, see vitamin B12 types.

Vitamin B12 Dosages

The recommended dosages of vitamin B12 depend entirely on the reason for use and the absorption ability of the person taking them. The dosages range hugely here, from 3 µg as the smallest dose available for a simple coverage of the daily requirement, up to 5000 µg for therapeutic doses and treatment of difficult diseases. 

Most people can achieve a good B12 supply with supplements of a medium dosage of 100 – 250 mg. Further specific information regarding individual dosage levels can be found in the corresponding section of our website. 

Overdosing with Vitamin B12 and Side Effects

Vitamin B12 is water soluble, meaning that an overdose is simply and safely excreted in the urine via the kidneys. A vitamin B12 overdose is thus almost impossible, unlike the very real possibility of overdosing on fat soluble vitamins. Even in doses of over 10 mg a day, there have been no reports of toxic reactions in adults.  

In the field of nutritional medicine, vitamin B12 is sometimes administered in high doses of 10 – 5,000 μg per day. However, caution should be taken in these instances, as the kidneys must then discard high volumes of excess vitamins, which will strain them over time. 

Allergic reactions can (albeit rarely) occur from injections, but this is often a reaction to the additives and other pharmaceuticals present. In a few cases, acne has been reported as a result of vitamin B12 reactions. This is sometimes as a result of a cobalt allergy. 

Vitamin B Complex Including Folic Acid

Particularly in cases of absorption difficulties, more nutrients are often required and it may not be sufficient to simply increase your vitamin B12 supply. In such instances, it is advisable to undertake a more extensive analysis into the benefits that the other nutrients provide. Often it is the other vitamins of the vitamin B complex which are required, and these are also available in supplement combos. Ideally, any supplement combination should contain the following vitamins in the following formats:

  • Vitamin B1 (thiamin) as thiamin diphosphate
  • Vitamin B2 (riboflavin) as riboflavin 5 phosphate,
  • Vitamin B3 (niacin) as nicotinamide adenine dinucleotide phosphate
  • Vitamin B5 (pantothenic acid) as D-pantothenic acid
  • Vitamin B6 (pyridoxine) as pyridoxal 5 phosphate
  • Vitamin B7 (biotin) as D-biotin
  • Vitamin B9 (folic acid) as 5 methyltetrahydrofolate
  • Vitamin B12 as methylcobalamin (for an acute deficiency with a quicker effect), or as hydroxocobalamin (sustained release),
  • Additionally, inositol and choline are also beneficial


1Dr. Lothar Burgerstein, Handbuch Nährstoffe, Trias Verlag, 12. Aufl., S. 182ff.
2Prof. Dr. Helmut Heseker, Dipl. oec. troph. Beate Heseker; Die Nährwerttabelle, 2. Aufl., 2012, Neuer Umschau Buchverlag

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