Vitamin B12 protects cells and the brain and is involved in blood formation. If the reserves are depleted, this often remains unnoticed for a long time - and can have consequences.
Vitamin B12 – Vitamin for blood, brain and cells
Vitamin B12 is important for our cells, for blood formation, our brain and much more. Nevertheless, we often don't notice that our reserves are slowly depleting for years. What can help: Monitoring the vitamin supply and counteracting it with nutrition or supplements.
A lack of vitamin B12 is considered a typical vegan disorder - but it does not only affect them. One thing is for certain: The vitamin is mainly found in animal foods. Anyone who consumes vegan food must take it with food supplements. But even some vegetarians and omnivores lack vitamin B12. Really large amounts are mainly found in offal and fish, i.e. in foods that are not on the menu of many meat eaters. The risk groups also include pregnant women, the elderly, people with pancreatitis and diabetes mellitus type 2.
What you can expect in this article - At a glance:
Ingesting vitamin B12: The water-soluble vitamin protects nerve cells, helps with blood formation and supplies the body with energy. It is found almost exclusively in animal foods, especially meat and fish. Your body stores vitamin B12 in the liver for up to three years.
Vitamin B12 deficiency: A deficiency often develops in vegetarians and vegans who do not take vitamin B12 supplements, but also in older people and pregnant women. Certain diseases make vitamin B12 deficiency more likely, such as diabetes and pancreatitis.
Symptoms and consequences: A deficiency often occurs for many years without symptoms until the reserves are empty - which may be accompanied by nerve damage, anaemia and an increased risk of cardiovascular disease.
Test: You can have your vitamin B12 values tested with a blood sample. The holotranscobalamin value is considered a reliable early warning sign of an undersupply.
Treatment: If you know that you suffer from an undersupply, you can incorporate vitamin B12-rich foods into your diet in a targeted manner. You can compensate for a significant deficiency with dietary supplements. Capsules and drops are available, as well as high-dose injections, which are administered by physicians in cases of very severe deficiencies.
What is Vitamin B?
Vitamin B12 it is an essential vitamin. This means that your body cannot produce it itself and you have to consume it through food. Like the other B vitamins, it is also a water-soluble vitamin. Water-soluble vitamins are regularly excreted through the kidneys and urine. As a rule, they have to be continually consumed because the body cannot store them. With one exception: studies have shown that your body can store vitamin B12 in the liver for two to six years.
This is why vitamin B12 is also known as cobalamin because its chemical structure contains heavy metal cobalt. The biochemically active forms of vitamin B12 that are effective in the body are methylcobalamin and 5-adenosylcobalamin.
The body can directly utilize the biochemically active form of a nutrient - meaning it has an immediate effect.
Vitamin B12 is very sensitive to air and light. When you prepare a meal, for example by cooking, foods will lose about twelve per cent of their vitamin B12 content on average.
What effect does Vitamin B have on the body?
Vitamin B12 plays an important role in numerous metabolic processes. It is involved in folate metabolism, blood formation and the breakdown of fatty acids, among other things.
Additional central metabolic processes that involve vitamin B12:
- DNA formation
- Nerve protection and regeneration
- Cell division and respiration
- Synthesis of messenger substance
Vitamin B12 and folic acid metabolism
Like vitamin B12, folic acid belongs to the group of B vitamins. Previous names for folic acid were vitamin B9 and B11. A vitamin B12 deficiency causes a folic acid deficiency because the body needs vitamin B12 to convert folic acid into its active form. Among other things, a folic acid deficiency can lead to anaemia and increase the risk of cardiovascular disease. But be careful: an excess of folic acid can lead to a vitamin B12 deficiency.[3–6].
Vitamin B12 and blood formation
Vitamin B12 is an important aid in blood formation. It promotes the maturation process of the red blood cells, the erythrocytes. The vitamin is involved in the formation of DNA and in cell division and thus stimulates the production of red blood cells.[3–5]
Vitamin B12 and the neurons
Vitamin B12 is also known as the neuro vitamin. It is responsible for the production of the myelin sheath which surrounds the nerve cells as a membrane. Myelin protects the cells and supports the transmission of signals from cell to cell..
How do I consume Vitamin B12?
In order for vitamin B12 to perform its important functions in the body, it must be supplied via food or dietary supplements.
How is Vitamin B12 consumed via food?
The vitamin B12, which you ingest through your diet, first enters the stomach. There, the stomach acid releases it and binds it to certain proteins. In the intestine, the mucous membrane of the small intestine can then absorb the vitamin and pass it on to the blood. Transport proteins, the transcobalamins, then transport vitamin B12 into all cells of the body and into the liver.
Good to know: Your body absorbs only one to three percent of the vitamin B12 found in a meal. Therefore, it helps your intake if you eat vitamin B12-containing foods throughout the day.
If the important transport proteins occur too rarely, for example, due to a genetic defect, vitamin B12 cannot be distributed correctly in the body. This is one possible cause of a vitamin B12 deficiency.[4, 8, 9]
In order for vitamin B12 intake to work smoothly, the stomach, pancreas and intestines must work properly. If the function of one of these organs is impaired, this can lead to a vitamin B12 deficiency. The following diseases worsen the absorption of vitamin B12[3, 12, 14]:
- Gastritis, inflammation of the gastric mucosa.
- damage to the mucous membrane of the small intestine, such as Crohn's disease
- Pancreatitis, inflammation of the pancreas.
Good to know: About two to five micrograms of vitamin B12 are stored in the body. Half of them accumulate in the liver - and can remain there for almost three years[4, 8].
Which foods contain Vitamin B12?
Vitamin B12 is found mainly in animal foods such as meat, fish, eggs and milk. Algae is discussed as a vegan alternative. So far, however, researchers have only found a form of the vitamin in so-called nori algae, which humans may be able to absorb - however, the amounts are too small and not everyone is able to absorb this form of the vitamin. Vegans, therefore, need to consume food supplements or foods enriched with vitamin B12, for example, juices, in order to meet their needs.
The following table provides an overview of foods that contain a lot of vitamin B12. According to the German Nutrition Society, each adult has a daily requirement of 4.0 micrograms of vitamin B12[11–13].
Vitamin-B12-content per perving (micrograms per 100 grams=)
Meat and Fish
Beef liver - 91 µg
Swiss cheese – 3,1 µg
Veal liver– 60 µg
Camembert – 2,6 µg
Pork liver– 39 µg
Edam – 1,9 µg
Beef kidney – 33 µg
Cottage cheese – 2,0 µg
Mackerel– 9 µg
Chicken egg – 1,9 µg
Hering – 8,5 µg
Quark – 0,8 µg
Salmon - 4,7 µg
Whole milk – 0,4 µg
Tuna fish – 4,3 µg
Cream – 0,4 µg
Lamb– 2,7 µg
Yogurt – 0,4 µg
Beef tenderloin– 2,0 µg
Salami – 1,4 µg
Ham – 0,6 µg
Turkey breast – 0,5 µg
That's good to know: An overdose of vitamin B12 is almost impossible in a natural way. The body normally excretes excess vitamin B12 via the kidneys and urine. Only when you take high doses of vitamin B12 over a long period of time is it possible for the kidneys to be overdosed.
What is the daily requirement of Vitamin B12?
In order for vitamin B12 to perform all its functions in the body, we need to ingest it through food. At the beginning of 2019, the German Nutrition Society (DGE) significantly increased its recommendations for the daily intake of vitamin B12. It now recommends a daily intake of 4.0 micrograms for adolescents aged 13 and over and adults. The requirement for children depends on their age, for example, 0.5 micrograms for infants up to the age of four months and 3.5 micrograms for children between 10 and 13. Pregnant women need 3.5 micrograms, breastfeeding women 4.0 micrograms per day..
The US National Institutes of Health (NIH) recommends values that are significantly lower than the more recent recommendations of the DGE. For example, a daily intake of 2.4 micrograms of vitamin B12 should be guaranteed for adolescents aged 14 and over and adults. Pregnant women, on the other hand, should consume 2.6 micrograms per day and breastfeeding women 2.8 micrograms.
Recommendations for the daily intake of vitamin B12 (in micrograms, µg):
0.5 to 3.5 µg
0.4 to 1.8 µg
4.0 µg (after 13 years of age)
2.4 µg (after 14 years of age)
Can the body produce its own Vitamin B12?
Some animals, especially ruminants such as cows, can produce vitamin B12 themselves. Numerous bacteria live in their rumen and produce vitamin B12 from food, which is then absorbed into the bloodstream. This is also the reason why beef contains vitamin B12.
Can the human body also produce vitamin B12? Scientists are still discussing this. The intestinal bacteria in our digestive tract can probably produce vitamin B12 - but they do so in the wrong place, namely in the colon. However, vitamin B12 is absorbed into the bloodstream in the small intestine. Therefore, the vitamin produced does not get into the blood or liver. Instead, it is excreted through the stool. Whether the body's own production of vitamin B12 contributes to the supply of vitamin B12 is still controversial..
Did you know? Some vegetarian mammals do not get enough vitamin B12 from their regular diet. Among others, guinea pigs and rats have found an extremely unappetizing solution: They eat their feces, which contains vitamin B12 produced in the colon.
Vitamin-B12 deficiency - Causes
Vitamin B12 deficiency is a widespread problem. Studies have shown that around six per cent of people up to the age of 60 in the USA and Great Britain are not sufficiently supplied with vitamin B12, and older people even more frequently.
Many sufferers are probably not even aware that they lack an important vitamin. A vitamin B12 deficiency is usually not noticed for a long time. Since the liver stores the vitamin, it can take years for you to experience symptoms. The downside of this is that while the stores are secretly emptied, serious long-term health problems can occur, such as anaemia, nerve damage and reduced vision.[1, 3, 4]
What are the causes of a Vitamin-B12 deficiency?
Vitamin B12 deficiency can affect anyone. Those who have an unhealthy and one-sided diet may not get enough vitamin B12 and develop a deficiency in the long run. There are some risk groups that are frequently affected:
- Vegans and Vegetarians
- Older people
- Pregnant and breastfeeding women
- People after a stomach operation
- People with chronic pancreatitis or type 2 diabetes
- Chronically stressed people
Vegetarian and Vegan Diets
A common cause of vitamin B12 deficiency is a vegan or vegetarian diet. Vitamin B12 is found almost exclusively in animal foods, and vegans can only meet their needs with dietary supplements. Vegetarians, on the other hand, can fall back on cheese, milk, eggs and curd. However, these foods contain significantly lower amounts of vitamin B12 than meat and fish - even a vegetarian diet is associated with an increased risk of deficiency.
Researchers are currently investigating whether the demand could be met by plant foods such as mushrooms and algae. Certain algae, for example, contain vitamin B12, but research has shown that they do so in forms that the human organism cannot utilize. The same may be true for shiitake mushrooms, but studies are still ongoing[21, 22].
Nutrition is probably also the reason for the gender difference in vitamin B12 supply. A study by the American Society for Microbiology showed that men consume animal products such as meat more often than women. And according to the National Consumption Study II, men consume vitamin B12 more frequently than women[22, 23].
Did you know? According to statistics, about one million people in Germany now eat a vegan diet. There are about eight million vegetarians - every tenth German lives without meat.
Vitamin-B12 deficiency with increased age
Age is also a risk factor. In Germany, almost a quarter of people over the age of 65 suffer from a vitamin B12 deficiency. This is partly due to the fact that older people often suffer from chronic illnesses, take various medications and that their eating habits change with age[24, 25]. In addition, older people produce less gastric acid. However, stomach acid is necessary to release vitamin B12 from food so that it can later be absorbed into the blood..
Vitamin-B12 deficiency in pregnant and breastfeeding women
Pregnant and breastfeeding women not only have to provide themselves with vitamin B12 - their growing baby also wants its share. As a result, they have an increased need and should urgently avoid an undersupply. The vitamin B12 supply plays a decisive role in the physical and mental development of unborn and newborn children. In the worst case, extreme vitamin B12 deficiency during pregnancy can even lead to miscarriage.
Illness and Surgery
People who suffer from pancreatitis, an inflammation of the pancreas, often suffer from a vitamin B12 deficit. They lack the enzyme trypsin, which is necessary for vitamin B12 uptake.
Studies have also shown that people with diabetes mellitus type 2 who take the drug metformin often have their difficulties with vitamin B12. It appears that metformin interferes with the absorption of vitamin.
You should also ensure that you receive vitamin B12 via dietary supplements after surgical gastric removal. The stomach plays a decisive role in the utilization of vitamin B12; after removal or reduction, absorption is often impaired.
Vitamin-B12 deficiency - Symptoms and Consequences
The symptoms of vitamin B12 deficiency are varied and often non-specific, making it difficult to detect.
What are the symptoms of Vitamin-B12 deficiency?
Vitamin B12 is involved in numerous metabolic processes in the body and thus provides energy, among other things. A vitamin B12 deficiency impairs mental and physical performance and therefore leads to less energy. The following symptoms can also occur:
- Fatigue and exhaustion
- Headaches and difficulty concentrating
- Digestive problems
Even if none of the above symptoms are present: An extreme vitamin B12 deficiency can have health consequences if it remains undetected or untreated for a long time.
If the body lacks sufficient vitamin B12, cell division in the bone marrow is disturbed. As a result, fewer red blood cells can be produced there. The result: so-called pernicious anaemia, a special form of anaemia. This anaemia is accompanied by paleness, fatigue, reduced performance and concentration.
A vitamin B12 deficiency also impairs oxygen transport. Vitamin B12 helps to build iron into the blood - iron, in turn, transports oxygen through the body. Insufficient oxygen in the organism is associated with decreased performance and concentration, immunodeficiency, exhaustion and fatigue[1, 26].
Neurological disorders and Depression
Vitamin B12 is responsible for the protection of neurons. If the vitamin cannot fulfil this responsibility due to a deficiency, fewer nerve fibres are formed in the spinal cord. This can lead to neurological symptoms such as:
- Nervousness and irritability
- Pain, numbness or "tingling" in hands, arms, feet and legs
Scientists are still researching the exact connections between vitamin B12, folic acid and depression. A common theory is based on the amino acid homocysteine. If there is not enough vitamin B12 in the body, there is too much homocysteine - an excess of this amino acid can damage the tissue in the brain and disrupt signal transmission. This, in turn, leads to mood swings and depression.
It is also being investigated whether preparations containing vitamin B12, folic acid and vitamin B6 can relieve depressive symptoms. The results are not yet clear. Some researchers recommend taking folic acid (800 micrograms per day) and vitamin B12 (1 milligram per day) to support depression treatment.[32, 33].
Vitamin-B12 deficiency and dementia
The symptoms of a pronounced vitamin B12 deficiency are similar to those of other neurological diseases - pain and numbness, for example, can also occur in herniated discs. This is another reason why vitamin B12 deficiency is often diagnosed very late.
Over time, vitamin B12 deficiency can cause damage from impaired nerve cells and anaemia - and may make Alzheimer's disease more likely. The connections have not yet been clarified and studies have so far failed to produce consistent results. However, there are indications that an optimal supply of B vitamins and folic acid can contribute to mental fitness in old age..
Alzheimer's disease is a brain disorder that almost always occurs in people over the age of 60. According to one study, it affects 14 percent of people over 70 and 37 percent of people over 90. Alzheimer's disease mainly manifests itself in memory, orientation and speech disorders as well as personality changes.
Vitamin-B12 deficiency and cardiovascular diseases
Vitamin B12 deficiency may contribute to the development of cardiovascular diseases such as cardiac insufficiency, stroke and heart attack.
What does vitamin B12 have in common with the cardiovascular system? It is primarily the amino acid homocysteine. Vitamin B12 breaks down homocysteine and converts it into other substances that contribute to the folic acid metabolism. If your body does not have enough vitamin B12 available, it breaks down less homocysteine. The concentration of the amino acid increases - and with it the risk of arteriosclerosis, i.e. calcification and narrowing of the blood vessels. This is one of the strongest risk factors for heart attack, stroke and other cardiovascular diseases.
Good to know: Cardiovascular diseases are responsible for one third of deaths worldwide - and the trend is rising.
Other possible causes of a Vitamin-B12 deficiency
Reduced vision may also be a sign of cobalamin deficiency. The involvement of vitamin B12 in certain messenger substances and hormones can also lead to psychological disorders such as depression and psychosis. If there is a lack of vitamin B12, energy metabolism is also disturbed, which can lead to muscle weakness, exhaustion, fatigue and lack of concentration. A deficiency can also manifest itself in digestive disorders such as loss of appetite, diarrhoea, constipation and inflammatory reactions in the mouth, stomach and intestines.
Vitamin B12 – Test
A blood test will tell you more about your Vitamin B12 supply. Various levels can be measured. Holo-Transcobalamin (Holo-TC) is a particularly meaningful parameter. Holo-Transcobalamin is the transport form of vitamin B12, which binds to proteins in the blood. It is the only form that can be absorbed by all cells of the body. A low Holo-TC level is an early warning sign of a vitamin B12 deficiency.
How can I test my Vitamin B12 level?
You can have a vitamin B12 test performed by a physician or alternative practitioner, among others. Another alternative is a home test, such as our cerascreen® Vitamin B12 Test.
For the test, you remove a few drops of blood yourself with a finger prick and send your blood sample to our specialist laboratory. After the evaluation, you will receive a comprehensive result report with your Holo-Transcobalamin level as well as concrete recommendations for action to improve your vitamin B12 level.
Vitamin-B12 deficiency - Treatment
If you have noticed an insufficient supply of vitamin B12 or a vitamin B12 deficiency, the solution is clear: You have to increase your supply of vitamin B12. Which steps you should take depends on the extent of the undersupply. If you suffer from a severe deficiency, you should consult a doctor to check whether the deficiency has possible consequences for your health.
Generally, there are three different ways to improve vitamin B12 levels:
- Deliberately include more vitamin B12-rich foods in your diet
- Use vitamin B12 supplements in the form of tablets, capsules, or drops.
- Get injections of high-dose vitamin B12 administered to you
How do I meet my daily requirements with food?
Vitamin B12 from food is found exclusively in animal foods. If you are an adult and are not breastfeeding, you can meet your daily requirements with 100 grams of tuna, 150 grams of lamb or 100 grams of salmon. Vegetarian alternatives are 200 grams of cottage cheese or two chicken eggs..
However, keep in mind that vitamin B12 can be lost depending on how you prepare a food. The vitamin is very sensitive to heat and light. Heat can destroy the vitamin, so roasting or cooking reduces the vitamin B12 content of food.
When will I receive Vitamin-B12 injections?
Vitamin B12 can also be injected into the muscle. These injections are very high doses. Physicians generally administer them to quickly replenish empty vitamin B12 reserves. In this case, you will usually receive an injection once a month. Vitamin B12 injections are particularly suitable for people suffering from digestive disorders, which means that not enough vitamin B12 enters the bloodstream from the stomach.
In order to compensate for a vitamin B12 deficiency, you can consume high-dose preparations. These dietary supplements are usually available in the form of capsules or drops and are often vegan.
Good vitamin B12 preparations contain the vitamin in one of its active forms, methylcobalamin or adenosylcobalamin. This is referred to as high bioavailability - the body can use the preparation quickly and effectively[3, 36].
Supplements should not contain any additives that could interfere with the action of the vitamin. The combination with substances that promote absorption by the body is again recommended. Vitamin B12 works well with other B vitamins and folic acid.
How do I consume Vitamin-B12 preparations?
According to various health authorities and studies, an amount of 500 to 2,000 micrograms of vitamin B12 per day is recommended. It is not possible to say exactly how much you will need to raise your levels. This varies depending on how well you are supplied with the vitamin. For example, it can make sense to take a dose of 1,000 micrograms daily at first, then weekly later and then monthly once the vitamin level has stabilized again[36, 37].
Supplementing Vitamin B12 with toothpaste?
Meeting your vitamin B12 needs while brushing your teeth? According to new studies, this may actually work. Toothpaste enriched with vitamin B12 was able to improve the B12 values of the study participants. The vitamin is absorbed through the oral mucosa during tooth brushing. This is advantageous for people whose gastrointestinal tract is disturbed and who cannot effectively absorb the preparations from drops and capsules[39, 40].
Can I overdose on Vitamin B12?
So far, there have been no reports of overdoses of vitamin B12. The body can usually simply excrete excess water-soluble vitamin via the kidneys. However, don't experiment: When taking dietary supplements, follow your doctor's, therapist's or supplement manufacturer's recommendations or instructions. It is best to perform a vitamin B12 test to find out if you need to improve your levels.
Vitamin B12 – At a glance
What is Vitamin B12?
Vitamin B12 is a water-soluble vitamin that you need to consume through your diet or dietary supplements.
What does Vitamin B12 do for your body?
The main tasks of the vitamin include blood formation, protection of neurons, cell division and support of folic acid metabolism.
How do I ensure that I receive enough Vitamin B12?
Vitamin B12 is found in animal foods. Whether you can also meet your needs with plant foods such as algae or fungi needs to be investigated further. Pregnant women, nursing mothers, seniors and people with gastrointestinal diseases need more vitamin B12.
What are the causes of a Vitamin-B12 deficiency?
Frequently, a vegan, vegetarian or simply inadequate diet leads to a deficiency. Other causes are drugs that inhibit gastric acid, certain diseases such as diabetes and pancreatitis, and genetic metabolic disorders.
What are the symptoms of a Vitamin-B12 deficiency?
Vitamin B12 deficiency is associated with depression, digestive problems, anaemia, poor concentration and neurological disorders. A severe deficiency can reduce performance and promote the development of cardiovascular disease and dementia.
How can I combat a Vitamin-B12 deficiency?
If you have detected a deficiency, for example through a blood test, you can take countermeasures with a targeted diet rich in vitamin B12 or resort to dietary supplements or injections.
What should I know about zinc preparations?
You should only consume preparations if you have a zinc deficiency. Otherwise, you run the risk of zinc poisoning. Compounds such as zinc histidine, gluconate and bisglycinate are most suitable. It is not recommended to take high amounts of medications or other minerals at the same time. The administration should be discussed with a doctor.
- Folate, I. of M. (US) S.C. on the S.E. of D.R.I. and its P. on, Vitamins, O.B., Choline, A.: Estimation of the Period Covered by Vitamin B12 Stores. National Academies Press (US) (1998)
- W. Kaim, B. Schwedersk: Bioanorganische Chemie – Zur Funktion chemischer Elemente in Lebensprozessen. Teubner (2005)
- Die ganze Welt der Vitamine, Mineralstoffe und Enzyme. garant Verlag GmbH, Renningen (2016)
- Kasper, H., Burghardt, W.: Ernährungsmedizin und Diätetik. Elsevier, Urban & Fischer, München (2014)
- Arens-Azevêdo, U., Pletschen, R. und Schneider, G.: Ernährungslehre: zeitgemäß, praxisnah. Bildungsverlag EINS GmbH., Köln (2011)
- Vitamin B12 | DACH Liga Homocystein, http://www.dach-liga-homocystein.org/content/vitamin-b12
- Myelin, http://www.nationalmssociety.org/What-is-MS/Definition-of-MS/Myelin
- Froese, D.S., Gravel, R.A.: Genetic disorders of vitamin B12 metabolism: eight complementation groups – eight genes. Expert Rev Mol Med. 12, (2010). doi:10.1017/S1462399410001651
- Ärzteblatt, D.Ä.G., Redaktion Deutsches: Ursachen und frühzeitige Diagnostik von Vitamin-B12-Mangel, https://www.aerzteblatt.de/archiv/61696/Ursachen-und-fruehzeitige-Diagnostik-von-Vitamin-B12-Mangel
- Vitamin B12-Versorgung bei veganer Ernährung: So geht’s!, https://www.peta.de/b12#.WrPEPojwa72
- Deutsches Grünes Kreuz für Gesundheit e.V.: Vorkommen von Vitamin B12, https://dgk.de/gesundheit/mikronaehrstoffe/lexikon/vitamine/vitamin-b-12-cobalamin/vorkommen-von-vitamin-b12.html
- National Institutes of Health: Office of Dietary Supplements - Vitamin B12, https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/
- Deutsche Forschungsanstalt für Lebensmittelchemie: Der kleine Souci/Fachmann/Kraut. Lebensmitteltabelle für die Praxis. Wissenschaftliche VErlagsgesellschaft Stuttgart
- Vitamin B₁₂, https://www.dge.de/wissenschaft/referenzwerte/vitamin-b12/
- Institute of Medicine. Food and Nutrition Board: Dietary Reference Intakes: Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline, (1998)
- Kon, S. K.; Porter, J. W. G.: The intestinal synthesis of vitamins in the ruminant. Vitamins and hormones.
- Degnan, P.H., Taga, M.E., Goodman, A.L.: Vitamin B12 as a modulator of gut microbial ecology. Cell Metab. 20, 769–778 (2014). doi:10.1016/j.cmet.2014.10.002
- Rowley, C.A., Kendall, M.M.: To B12 or not to B12: Five questions on the role of cobalamin in host-microbial interactions. PLOS Pathogens. 15, e1007479 (2019). doi:10.1371/journal.ppat.1007479
- Allen, L.H.: How common is vitamin B-12 deficiency? Am J Clin Nutr. 89, 693S-696S (2009). doi:10.3945/ajcn.2008.26947A
- Elmadfa, I.: Ernährungslehre. Verlag Eugen Ulmer Stuttgart (2015)
- Watanabe, F., Yabuta, Y., Bito, T., Teng, F.: Vitamin B12-Containing Plant Food Sources for Vegetarians. Nutrients. 6, 1861–1873 (2014). doi:10.3390/nu6051861
- Watanabe, F.: Vitamin B12 sources and bioavailability. Exp. Biol. Med. (Maywood). 232, 1266–1274 (2007). doi:10.3181/0703-MR-67
- American Society for Microbiology, https://www.asm.org/index.php/component/content/article/114-unknown/unknown/4739-the-difference-in-eating-habits-between-men-and-women?highlight=YToyOntpOjA7czozOiJtZW4iO2k6MTtzOjQ6Im1lYXQiO30=
- Monate, * Alle Preise verstehen sich zzgl der gesetzlichen MwSt Mindestlaufzeit 12: Lebenseinstellung - Veganer in Deutschland 2017 | Statistik, https://de.statista.com/statistik/daten/studie/445155/umfrage/umfrage-in-deutschland-zur-anzahl-der-veganer/
- Nutrients | Free Full-Text | Prevalence and Predictors of Subclinical Micronutrient Deficiency in German Older Adults: Results from the Population-Based KORA-Age Study, http://www.mdpi.com/2072-6643/9/12/1276
- Nahrungsergänzung, https://www.bzfe.de/inhalt/pressemeldung-6785.html
- Office of Dietary Supplements - Vitamin B12, https://ods.od.nih.gov/factsheets/VitaminB12-Consumer/
- Körner, U.: Ernährungsberatung in Schwangerschaft und Stillzeit. MVZ-Medizinverlage Stuttgart
- Toskes, P.P., Deren, J.J., Conrad, M.E.: Trypsin-Like Nature of the Pancreatic Factor That Corrects Vitamin B12 Malabsorption Associated with Pancreatic Dysfunction. J Clin Invest. 52, 1660–1664 (1973)
- Ärzteblatt, D.Ä.G., Redaktion Deutsches: Vitamin-B12-Mangel durch Metformin, https://www.aerzteblatt.de/nachrichten/41325/Vitamin-B12-Mangel-durch-Metformin
- Symptoms, https://www.nhs.uk/conditions/vitamin-b12-or-folate-deficiency-anaemia/symptoms/
- Bhatia, P., Singh, N.: Homocysteine excess: delineating the possible mechanism of neurotoxicity and depression. Fundamental & Clinical Pharmacology. 29, 522–528 (2015). doi:10.1111/fcp.12145
- Lim, S.Y., Kim, E.J., Kim, A., Lee, H.J., Choi, H.J., Yang, S.J.: Nutritional Factors Affecting Mental Health. Clinical Nutrition Research. 5, 143–152 (2016). doi:10.7762/cnr.2016.5.3.143
- Coppen, A., Bolander-Gouaille, C.: Treatment of depression: time to consider folic acid and vitamin B12. J. Psychopharmacol. (Oxford). 19, 59–65 (2005). doi:10.1177/0269881105048899
- Das Wichtigste über die Alzheimer-Krankheit . DAlzG, https://www.deutsche-alzheimer.de/die-krankheit/die-alzheimer-krankheit.html
- Are You Vitamin B12 Deficient?, https://draxe.com/b12-injections/
- Butler, C.C., Vidal-Alaball, J., Cannings-John, R., McCaddon, A., Hood, K., Papaioannou, A., Mcdowell, I., Goringe, A.: Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency: a systematic review of randomized controlled trials. Fam Pract. 23, 279–285 (2006). doi:10.1093/fampra/cml008
- Vidal-Alaball, J., Butler, C.C., Cannings-John, R., Goringe, A., Hood, K., McCaddon, A., McDowell, I., Papaioannou, A.: Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency. Cochrane Database Syst Rev. CD004655 (2005). doi:10.1002/14651858.CD004655.pub2
- Vitamin-B12-angereichertes Zahngel für Vegetarier - BZfE, https://www.bzfe.de/inhalt/vitamin-b12-angereichertes-zahngel-fuer-vegetarier-alternative-zu-nahrungsergaenzungen-29020.html
- Vegane Ernährung, https://www.ernaehrungs-umschau.de/print-artikel/11-07-2014-vegane-ernaehrung-teil-2/
- Read “Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline” at NAP.edu.