Vitamin B12 is an essential vitamin that is vital for many functions in the body. Among other things, it plays a central role in the formation of red blood cells, in cell renewal and the functioning of the nervous system. A severe deficiency may entail health risks. In this article, you will learn more about the causes, symptoms and treatment of vitamin B12 deficiency.
Our body has a vitamin store, which means that a vitamin B12 deficiency only develops quite slowly.
Vegans are particularly at risk of developing vitamin B12 deficiency due to their purely plant-based diet, since vitamin B12 is almost exclusively found in products of animal origin.
In highly developed countries, inadequate vitamin B12 intake through food is extremely rare, except for vegans and strict vegetarians who consume few dairy products or eggs. Worldwide, there are an estimated 75 million voluntary vegetarians as well as 1.45 billion people who live as vegetarians due to a lack of options. A strictly vegetarian (vegan) diet provides a maximum of 0.5 μg vitamin B12 per day, which is why this form of diet is one of the main risk factors for vitamin B12 deficiency.
Vegetarians (lacto-, ovo- and rarely also ovo-lacto-vegetarians) often have subclinical deficiencies that manifest as elevated methylmalonic acid or homocysteine levels. The offspring of vegan or strictly vegetarian mothers can also be affected by a B12 deficiency.
A vitamin B12 deficiency is more likely to occur in the elderly or in persons with gastrointestinal disorders. With age, the performance of the gastrointestinal tract decreases, which means that vitamins can no longer be absorbed as well. However, deficiency symptoms may also occur when taking medications, for example for diabetes or in the presence of too much stomach acid, regular alcohol consumption or after surgery on the gastrointestinal tract. Pregnant and breastfeeding women should also ensure a good B12 supply, as B12 is essential for the appropriate development of the foetus and child.
Another common cause of vitamin B12 deficiency is the impaired absorption of vitamins, for example due to a deficiency in the so-called intrinsic factor. This is a protein building block that is formed in the stomach cells of our body. The intrinsic factor allows vitamin B12 to be absorbed from our food. Older people in particular often suffer from a deficiency of the intrinsic factor. Chronic inflammation of the gastric mucosa can also lead to a vitamin B12 deficiency. In such a situation, the intrinsic factor is produced in a reduced quantity.
The first signs of a vitamin B12 deficiency are often non-specific and subtle. These include fatigue, weakness, lack of drive, concentration disorders as well as dizziness and headaches. Since vitamin B12 is important for blood production, a deficiency can also lead to anaemia. Typical signs of anaemia are pale skin, shortness of breath and tachycardia.
In the long term, an untreated vitamin B12 deficiency can damage the nerves and cause symptoms such as numbness, tingling and muscle weakness due to the ongoing anaemia. Possible consequences include depression, confusion and impaired brain function.
Since the symptoms of vitamin B12 deficiency are often ambiguous, a blood test is indispensable for diagnosis. Here, the standard vitamin B12 value in the blood serum alone is not sufficient, since it is a relatively late and non-specific marker.
Instead, experts recommend determining additional biomarkers such as holotranscobalamin II (Holo-TC) and methylmalonic acid (MMA), which provide a more reliable picture in the combination. Low Holo-TC values below 35 pmol/l indicate an impending deficiency as the earliest marker, while elevated MMA values above 271 nmol/l indicate an already empty vitamin B12 store.
A balanced diet is the best way to prevent vitamin B12 deficiency, but only for people who consume foods of animal origin. This is because the water-soluble vitamin is only found in sufficient quantities in meat, poultry, fish, eggs and dairy products and as a trace element in milk fermented plant-based foods. It can also be obtained from foods fortified with synthetic vitamin B12, such as breakfast cereals and spreads.
To prevent a vitamin B12 deficiency, it is recommended that vegans and persons with a very low intake of foods of animal origin take supplements with vitamin B12 or specifically resort to vitamin B12 enriched foods.
According to the German Nutrition Society (DGE), the estimated value for an appropriate supply is 4 micrograms – it is assumed that small amounts of B12 are consumed several times a day in a diet with animal foods, which are absorbed in the body by an active absorption path. In the case of additional, one-time supplementation due to plant-based diets, however, the body uses the passive absorption path for the vitamin, for which higher doses are necessary, because this passive diffusion is less efficient.
Further reading:
Briani, C. et al. 2013. Cobalamin deficiency: clinical picture and radiological findings. Nutrients. 5(11):4521–39.
Obersby, D. et al. 2013. Plasma total homocysteine status of vegetarians compared with omnivores: a systematic review and meta-analysis. Br J Nutr. 109(5):785–94.
Hughes, C. F. et al. 2013. Vitamin B12 and ageing: current issues and interaction with folate. Ann Clin Biochem. 50(Pt Nr):315–29.
Thakkar, K., Billa G. 2015. Treatment of vitamin B12 deficiency – Methylcobalamine? Cyancobalamine? Hydroxocobalamin? – clearing the confusion. Eur J Clin Nutr. 69(1):1–2.
Wald, D. S. et al. 2011. Serum homocysteine and dementia: meta-analysis of eight cohort studies including 8669 participants. Alzheimers Dement. 7(4):412–7.
Christine, C. W. et al. 2018. Vitamin B12 and Homocysteine Levels Predict Different Outcomes in Early Parkinson’s Disease. Mov. Disord. 33(5):762–70.
Douaud, G. et al. 2013. Preventing Alzheimer’s disease-related gray matter atrophy by B-vitamin treatment. Proc Natl Acad Sci U S A. 110(23):9523–8.
Smith, A. D. et al. 2010. Homocysteine-lowering by B vitamins slows the rate of accelerated brain atrophy in mild cognitive impairment: a randomized controlled trial. PLoS ONE. 5(9):e12244.
Syed, E. U. et al. 2013. Vitamin B12 supplementation in treating major depressive disorder: a randomized controlled trial. Open Neurol J. 7:44–8.
Yang, G.-T. et al. 2018. Correlation between serum vitamin B12 level and peripheral neuropathy in atrophic gastritis. World J Gastroenterol. 24(12):1343–52.
Rodríguez de Santiago, E. et al. 2015. Pernicious anemia. From past to present. Rev Clin Esp. 215(5):276–84.
Obeid, R. et al. 2015. Cobalamin coenzyme forms are not likely to be superior to cyano- and hydroxyl-cobalamin in prevention or treatment of cobalamin deficiency. Mol Nutr Food Res. 59(7):1364–72.
