Table of contents
1 Vitamin B12 deficiency symptoms
A vitamin B12 deficiency is difficult to recognize when there is a lot of folic acid
2 You need vitamin B12 for this
3 Vitamin B12: Fallacies, assumptions and proven effects
A vitamin B12 deficiency leads to physical weakness and tiredness. However, this does not make vitamin B12 a workout booster! Reduces homocysteine levels and thus promotes a healthy cardiovascular system A vitamin B12 deficiency could lead to Alzheimer's and dementia
4 Recommended daily requirement of vitamin B12
5 Sources of vitamin B12
6 Risk groups for vitamin B12 deficiency
Vegetarians and vegans are particularly at risk because they do not eat animal products Vegetarian or vegan pregnant and breastfeeding women and their children Older adults with atrophic gastritis use less B12 People with gastrointestinal diseases store B12 inefficiently Patients who have undergone gastric or intestinal surgery may absorb B12 poorly People with impaired red blood cell formation (pernicious anemia) cannot absorb vitamin B12 well
7 Is it possible to overdose on vitamin B12?
Vitamin B12 deficiency is caused by too high hygiene standards!
8 The four types of vitamin B12
Cyanocobalamin Methylcobalamin Adenosylcobalamin Hydroxocobalamin
9 Conclusion

Vegans and vegetarians are particularly at risk of consuming too little B12. A healthy vitamin B12 level allows you to get the best out of your body. Vitamin B12 deficiency symptoms are varied and can be very serious. We explain what types of vitamin B12 there are and how you can prevent a vitamin B12 deficiency.

Vitamin B12 deficiency symptoms

The symptoms associated with a vitamin B12 deficiency are extremely varied and can affect your entire body in many different ways. Vitamin B12 deficiency primarily manifests as megaloblastic anemia (impaired red blood cell production), fatigue, weakness, constipation, loss of appetite and unexplained weight loss. As these symptoms can be due to many causes and only a few people are aware of the possibility of vitamin B12 deficiency, it usually remains undetected for a long time.3 In advanced cases, neurological symptoms such as numbness or tingling sensations in the arms and legs or balance problems can occur.4 A person's cognition can also be affected by vitamin B12 deficiency. This usually results in confusion, dementia, limited memory or depression.

The neurological symptoms of vitamin B12 deficiency can also occur without anemia, which is why early diagnosis and intervention are important to avoid permanent damage. In infancy, signs of vitamin B12 deficiency include movement disorders, developmental delays and impaired red blood cell formation.5

If a doctor identifies a serious vitamin B12 deficiency as a result of a blood test, the patient is usually given a vitamin B12 injection. The injection bypasses absorption barriers in the stomach, allowing the body to absorb vitamin B12 more quickly and efficiently. After this initial intervention, the patient is usually prescribed tablets to take orally. If the patient's intestinal bacteria are so damaged that they cannot absorb the vitamin B12 from the tablets efficiently, they are given regular intramuscular vitamin B12 injections.6

A vitamin B12 deficiency is difficult to detect if there is a lot of folic acid

If a person with a vitamin B12 deficiency consumes increased amounts of folic acid, it makes it more difficult for doctors to make a correct diagnosis. In this case, folic acid corrects the impaired formation of red blood cells caused by the vitamin B12 deficiency. However, the neurological damage caused by vitamin B12 deficiency is not corrected by folic acid.7 There is also evidence that elevated folate levels may exacerbate the cognitive impairment associated with vitamin B12 deficiency.8 A vitamin B12 deficiency that remains untreated almost always leads to permanent nerve damage and can also be life-threatening for years. It is therefore advisable not to consume more than 1 mg of folic acid per day.

You need vitamin B12 for this

Your body needs vitamin B12 to form red blood cells and DNA. It is therefore essential for a healthy, normally functioning nervous system and brain. In addition, the metabolism of cells in your body is directly influenced by vitamin B12, as it plays another important role in the production of fatty acids. Your body needs vitamin B12 to be able to absorb folic acid effectively. Therefore, a B12 deficiency can also cause a folic acid deficiency.9

In a nutshell: Vitamin B12 is involved in many of your body's vital mechanisms and is therefore by definition a vital substance (vitamin).

Vitamin B12: Fallacies, assumptions and proven effects

A vitamin B12 deficiency leads to physical weakness and tiredness. However, this does not make vitamin B12 a workout booster!

As vitamin B12 plays an important role in your body's energy metabolism, it is often marketed as an energy booster for endurance sports. These promising claims are based on the fact that a vitamin B12 deficiency leads to megaloblastic anemia, which makes the body feel tired and weak. However, there is no evidence that vitamin B12 supplementation can improve athletic performance in the absence of vitamin B12 deficiency.10

Reduces homocysteine levels and thus promotes a healthy cardiovascular system

In addition to vitamin B6 and folic acid, vitamin B12 also influences the homocysteine metabolism by lowering it. Homocysteine is an amino acid that is typically found in the blood. Taking a combination supplement containing folic acid and vitamin B12 has been shown to reduce homocysteine levels in both healthy people and those affected by diabetes or vascular disease.11 In addition to high LDL levels, low HDL levels, obesity, diabetes and high blood pressure, a high homocysteine level is a proven risk factor for cardiovascular disease12 (The number 1 cause of death worldwide!13). Vitamin B12 is therefore important, among other things, to counteract chronic diseases.

A vitamin B12 deficiency could lead to Alzheimer's and dementia

A vitamin B12 deficiency is associated with more homocysteine in the blood. This in turn can reduce the levels of various substances that are responsible for the metabolism of our neurotransmitters.14 Elevated homocysteine levels have already been linked to an increased risk of Alzheimer's disease or dementia.15 Separately, low vitamin B12 levels have also been associated with worsening cognition16

Despite these proven correlations, research has not yet shown that vitamin B12 can affect cognition preventively or therapeutically independent of its influence on homocysteine levels.17 While a supplement of vitamin B12 and folic acid reduced homocysteine levels by 36%, the same supplement and vitamin B12 alone did not improve cognitive function after 24 weeks.18 There is also a strong need for research to assess whether vitamin B12 can directly influence cognitive function and dementia.19

Recommended daily requirement of vitamin B12

Age/phase of life Recommended daily requirement of vitamin B12 in μg
0 - 4 months 0,5
4 - 12 months 1,4
1 - 4 years 1,5
4 - 7 years 2,0
7 - 10 years 2,5
10 - 13 years 3,5
13 - 15 years 4,0
15 - 19 years 4,0
19 - 25 years 4,0
25 - 51 years 4,0
51 - 65 years 4,0
65+ years 4,0
During pregnancy 4,5
During breastfeeding 4,5

Sources of vitamin B12

Vitamin B12 is most commonly found in animal products such as eggs, milk and meat. Plant sources of vitamin B12 include various algae (spirulina, nori, etc.). However, the B12 content in algae varies greatly and depends on many environmental factors. Recently, plenty of vitamin B12 was found in duckweed, but more research is needed here, as the vitamin B12 content may vary just as much as in algae.21

It is therefore recommended that people with a purely plant-based diet supplement vitamin B12 in tablet form or consume vitamin B12-fortified breakfast cereals, astronaut food or plant-based milk drinks (e.g. soy, rice, oat or almond milk). The amount of vitamin B12 in these fortified foods also varies greatly, so you should always check the nutritional information. Alternatively, there are also some yeast products that contain reliable amounts of vitamin B12.22

Foodstuffs Vitamin B12 content per 100 g Percentage of the average recommended daily intake
Mussels 98.9 μg 4120%
Octopus 36 μg 1500%
Oysters 28.8 μg 1200%
Pork liver 20.1 μg 837%
Mackerel 19 μg 792%
Herring 18.7 μg 779%
Liver sausage / spreadable sausage 13.5 μg 561%
King crab 11.5 μg 479%
Tuna 10.9 μg 453%

Risk groups for vitamin B12 deficiency

In many cases, the cause of a diagnosed vitamin B12 deficiency remains unexplained. The most common causes of vitamin B12 deficiency are

  • Poor absorption of vitamin B12 after surgery: An affected person may consume plenty of vitamin B12, but it does not pass from the stomach into the bloodstream where it should be utilized.
  • Poor absorption of B12 due to diet: Due to a poor or inconsistent diet, the gut biome is damaged and vitamin B12 is inefficiently absorbed.
  • Nutritional vitamin B12 deficiency: Little or no B12 is consumed for weeks or months24

The following demographics are among the risk groups for vitamin B12 deficiency:

Vegetarians and vegans are particularly at risk as they do not eat animal products

Vegetarians and vegans should keep a particularly close eye on their vitamin B12 levels, as the most reliable food sources of vitamin B12 are animal products.25

Vegetarian or vegan pregnant and breastfeeding women and their children

An undetected and untreated vitamin B12 deficiency in infants can lead to severe and permanent neurological damage. Vitamin B12 crosses the placenta during pregnancy and is contained in breast milk. Infants who receive only breast milk from women who do not consume animal products have very limited reserves of vitamin B12 and develop vitamin B12 deficiency within months of birth.26 Pregnant and breastfeeding women who follow a strict vegetarian or vegan diet should seek advice from a pediatrician regarding vitamin B12 supplementation for their infants and children.27

Older adults with atrophic gastritis use less B12

Approximately 15 to 30% of all older adults suffer from atrophic gastritis. This disease reduces the secretion of acid in the stomach. As a result, food and food supplements cannot be sufficiently broken down and utilized. This leads to malabsorption of vitamin B12.28 Indirectly, this condition can also increase the daily requirement of the person affected, as less hydrochloric acid in the intestine promotes the growth of intestinal bacteria. These intestinal bacteria consume vitamin B12, leaving less vitamin B12 for the body itself. Although these individuals are often unable to absorb vitamin B12 from natural sources, synthetic forms of B12 (cyanocobalamin) are not usually affected.29

People with gastrointestinal diseases store B12 inefficiently

People with diseases of the gastrointestinal tract (e.g. Crohn's disease or coeliac disease) are often unable to store vitamin B12 efficiently.30 Subtly reduced cognitive function due to early vitamin B12 deficiency may be the only initial symptom of these intestinal disorders, followed by megaloblastic anemia and dementia.

Patients who have undergone gastric or intestinal surgery can absorb B12 poorly

Gastrointestinal surgery, such as removal of a tumor or weight loss surgery, usually destroys cells that secrete hydrochloric acid and other substances important to the gut biome.31 Individuals undergoing certain gastrointestinal surgical procedures should be monitored for various nutritional deficiencies, including potential vitamin B12 deficiency, both before and after surgery.32

People with impaired red blood cell formation (pernicious anemia) cannot absorb vitamin B12 well

This disease also usually occurs in older people and is characterized by a lack of intrinsic factors in the intestine. People who suffer from pernicious anemia can only absorb vitamin B12 very poorly.33 Therefore, people with pernicious anemia are usually given vitamin B12 intramuscularly. However, since the absorption rate of B12 without the presence of intrinsic factors is around 1%, it is obvious that high oral doses could be an effective treatment method.

Can you overdose on vitamin B12?

You may be confused when you read that your vitamin B12 tablets contain hundreds or thousands of times the recommended daily requirement. Although overdosing on other vitamins can be life-threatening, there is no such danger with vitamin B12. Your body only takes as much vitamin B12 as it needs. The rest is excreted in the urine.

Vitamin B12 deficiency is caused by excessive hygiene standards!

B12 is produced by bacteria that live mainly in the soil. To produce vitamin B12, the bacteria need the mineral cobalt. Herbivorous animals ingest vitamin B12 by accidentally consuming small amounts of soil or feces from other animals. People who primarily eat commercially cultivated food have an increased risk of developing a vitamin B12 deficiency. This is due to hygiene standards and modern farming methods:

  • Intensive over-cultivation of fields removes cobalt from the soil. Bacteria that live in cobalt-poor soil cannot produce B12.
  • Even if fruit and vegetables are harvested from healthy, cobalt-rich soils, the B12-containing soil residues from the food are usually washed away during processing (due to strict hygiene regulations).

The four types of vitamin B12

Cyanocobalamin

Cyanocobalamin is a fully synthetic form of B12 and contains a cyanide molecule. This molecule makes cyanocobalamin the most stable of the four types of vitamin B12. Although cyanide (chlorine) is often referred to as a toxin, the cyanide content in cyanocobalamin is so low that it has not been shown to cause any physical harm. Cyanocobalamin is converted into methylcobalamin in your body.

Methylcobalamin

Methylcobalamin is the natural, active form of vitamin B12 that is found everywhere in your body. Multivitamin tablets with methylcobalamin are rather rare and usually more expensive than preparations with cyanocobalamin.

Adenosylcobalamin

Adenosylcobalamin is another form of B12 found in your body that your body needs for the energy metabolism of every cell. Although methylcobalamin and adenosylcobalamin are two different forms of vitamin B12 on a molecular level, your body can convert one form into the other as needed. Adenosylcobalamin is an extremely unstable molecule and is generally not used in food supplements.

Hydroxocobalamin

Hydroxocobalamin is the third natural form of vitamin B12. It is produced by intestinal bacteria that can convert parts of our food into hydroxocobalamin. However, this form of vitamin B12 can be produced artificially by cultivating microorganisms. After our intestinal bacteria have produced hydroxycobalamin, it is converted into methylcobalamin and adenosylcobalamin in our body.

Conclusion

Vitamin B12 is primarily required for the formation of red blood cells, the maintenance of a healthy nervous system and the synthesis of DNA.1 Vitamin B12 is essential for various vital mechanisms in your body. Only very few foods make it possible to absorb vitamin B12 vegan. There are four different forms of vitamin B12 that can be obtained from natural foods, supplements or medications2

Collapsible content

Sources

  1. Herbert V, Das K. Vitamin B12 in Modern Nutrition in Health and Disease. 8th ed. Baltimore, MD: Williams & Wilkins, 1994.
  2. Herbert V. Vitamin B12 in Present Knowledge in Nutrition. 17th ed. Washington, DC: International Life Sciences Institute Press, 1996.
  3. Bernard MA, Nakonezny PA, Kashner TM. The effect of vitamin B12 deficiency on older veterans and its relationship to health. J Am Geriatr Soc 1998;46:1199-206.
  4. Healton EB, Savage DG, Brust JC, Garrett TF, Lindenbaum J. Neurological aspects of cobalamin deficiency. Medicine 1991;70:229-44.
  5. Monsen ALB, Ueland PM. Homocysteine and methylmalonic acid in diagnosis and risk assessment from infancy to adolescent. Am J Clin Nutr 2003;78:7-21.
  6. Carmel R. How I treat cobalamin (vitamin B12) deficiency. Blood.2008;112:2214-21.
  7. Herbert V. Vitamin B12 in Present Knowledge in Nutrition. 17th ed. Washington, DC: International Life Sciences Institute Press, 1996.
  8. Johnson MA. If high folic acid aggravates vitamin B12 deficiency what should be done about it? Nutr Rev 2007;65:451-8.
  9. Bito, T., & Watanabe, F. (2016). Biochemistry, function, and deficiency of vitamin B12 in Caenorhabditis elegans. Experimental biology and medicine (Maywood, N.J.), 241(15), 1663-1668.
  10. Lukaski HC. Vitamin and mineral status: effects on physical performance. Nutrition. 2004;20(7-8):632-644. doi:10.1016/j.nut.2004.04.001
  11. Bronstrup A, Hages M, Prinz-Langenohl R, Pietrzik K. Effects of folic acid and combinations of folic acid and vitamin B12 on plasma homocysteine concentrations in healthy, young women. Am J Clin Nutr 1998;68:1104-10. 
  12. Schulz RJ. Homocysteine as a biomarker for cognitive dysfunction in the elderly. Curr Opin Clin Nutr Metab Care 2007;10:718-23.
  13. Mc Namara, K., Alzubaidi, H., & Jackson, J. K. (2019). Cardiovascular disease as a leading cause of death: how are pharmacists getting involved?. Integrated pharmacy research & practice, 8, 1-11.
  14. Hutto BR. Folate and cobalamin in psychiatric illness. Compr Psychiatry 1997;38:305-14.
  15. Seshadri S, Beiser A, Selhub J, Jacques PF, Rosenberg IH, D'Agostino RB, et al. Plasma homocysteine as a risk factor for dementia and Alzheimer's disease. N Engl J Med 2002;346:476-83.
  16. Clarke R, Birks J, Nexo E, Ueland PM, Schneede J, Scott J, et al. Low vitamin B-12 status and risk of cognitive decline in older adults. Am J Clin Nutr 2007;86:1384-91.
  17. Hvas AM, Juul S, Lauritzen L, Nexø E, Ellegaard J. No effect of vitamin B-12 treatment on cognitive function and depression: a randomized placebo controlled study. J Affect Disord 2004;81:269-73.
  18. Eussen SJ, de Groot LC, Joosten LW, Bloo RJ, Clarke R, Ueland PM, et al. Effect of oral vitamin B-12 with or without folic acid on cognitive function in older people with mild vitamin B-12 deficiency: a randomized, placebo-controlled trial. Am J Clin Nutr 2006;84:361-70.
  19. Clarke R. B-vitamins and prevention of dementia. Proc Nutr Soc 2008;67:75-81.
  20. D. (2020). Reference values for nutrient intake. Retrieved August 02, 2020.
  21. Obeid, R., Heil, S. G., Verhoeven, M., van den Heuvel, E., de Groot, L., & Eussen, S. (2019). Vitamin B12 Intake From Animal Foods, Biomarkers, and Health Aspects. Frontiers in nutrition, 6, 93.
  22. Watanabe, F., Yabuta, Y., Bito, T., & Teng, F. (2014). Vitamin B₁₂-containing plant food sources for vegetarians. Nutrients, 6(5), 1861-1873. 
  23. Watanabe, F., & Bito, T. (2018). Vitamin B12 sources and microbial interaction. Experimental biology and medicine (Maywood, N.J.), 243(2), 148-158. 
  24. Andrès E, Federici L, Affenberger S, Vidal-Alaball J, Loukili NH, Zimmer J, et al. B12 deficiency: a look beyond pernicious anemia. J Fam Pract 2007;56:537-42.
  25. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Thiamine, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academy Press, 1998.
  26. von Schenck U, Bender-Gotze C, Koletzko B. Persistence of neurological damage induced by dietary vitamin B12 deficiency in infancy. Arch Dis Childhood 1997;77:137-9.
  27. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Thiamine, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academy Press, 1998.
  28. Suter PM, Golner BB, Goldin BR, Morrow FD, Russel RM. Reversal of protein-bound vitamin B12 malabsorption with antibiotics in atrophic gastritis. Gastroenterology 1991;101:1039-45.
  29. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Thiamine, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academy Press, 1998.
  30. Andrès E, Federici L, Affenberger S, Vidal-Alaball J, Loukili NH, Zimmer J, et al. B12 deficiency: a look beyond pernicious anemia. J Fam Pract 2007;56:537-42.
  31. Sumner AE, Chin MM, Abraham JL, Gerry GT, Allen RH, Stabler SP. Elevated methylmalonic acid and total homocysteine levels show high prevalence of vitamin B12 deficiency after gastric surgery. Ann Intern Med 1996;124:469-76.
  32. Commonwealth of Massachusetts, Betsy Lehman Center for Patient Safety and Medical Error Reduction. Expert Panel on Weight Loss Surgery, Executive Report, 2007.
  33. Gueant JL, Safi A, Aimone-Gastin I, Rabesona H, Bronowicki J P, Plenat F, et al. Autoantibodies in pernicious anemia type I patients recognize sequence 251-256 in human intrinsic factor. Proc Assoc Am Physicians 1997;109:462-9.