Vitamin B12 Deficiency Weight Gain: Everything You Need to Know

Gewichtszunahme durch Vitamin B12 Mangel: Alles Wichtige

Vitamin B12 deficiency is an undersupply of the body that often occurs in connection with an unbalanced diet, a vegan diet or an illness. Weight gain can be another symptom of such a disease and can occur together with vitamin B12 deficiency as a result.

This article is intended to give you an understanding of the essential functions of vitamin B12, as well as the causes and consequences of a deficiency. Particular attention is paid to the connection with weight gain. In addition, we give you valuable tips on how to successfully treat a vitamin B12 deficiency or take preventive measures in this regard.

the essentials in brief

  • Vitamin B12 cannot be produced by humans and must therefore be ingested through food or dietary supplements. Almost exclusively animal products contain vitamin B12.
  • Vitamin B12 deficiency is common in the elderly, pregnant and breastfeeding women, vegetarians and vegans, and people with gastrointestinal diseases. Treatment is via dietary changes, dietary supplements or medication.
  • Vitamin B12 deficiency can have serious consequences as the vitamin is involved in many important processes in the body. It is therefore advisable to know whether you are consuming enough vitamin B12 or whether the body can absorb it.

Definition: What is vitamin B12?

Vitamin B12 is an essential vitamin for the human body that is supplied through food. Along with other vitamins, B12 belongs to the group of water-soluble vitamins, which means that it is excreted via the kidneys and urine. Accordingly, the vitamins have to be replenished regularly, since the body cannot store the substances. Vitamin B12 is the exception: According to studies, the body can store vitamin B12 in the body for two to six years. (1)

Vitamin B12 contains the two biochemically active forms methylcobalamin and 5-adenosylcobalamin. They unfold their effect immediately after ingestion, a property of biochemically active forms of nutrients. (2)

Like many other vitamins and minerals, vitamin B12 is very sensitive to air and light. This means that foods containing vitamin B12 lose some of it during cooking. According to experts, an average of 12 percent of the vitamin B12 content is lost during preparation. (3)

Background: What you should know about vitamin B12 deficiency

Now that we know what vitamin B12 is, some background information is needed before we share tips for solving vitamin B12 deficiency associated with weight gain.

We want to answer these frequently asked questions for you in the following paragraphs.

What is the function of vitamin B12 in the body?

As already mentioned, vitamin B12 is essential for human survival, so a deficiency in this compound should be taken very seriously.

The vitamin plays a major role in numerous metabolic reactions. In the next sections we show the most important functions. (3)

  • Blood formation / folic acid: Vitamin supports blood formation via folic acid and promotes the maturation process of the red blood cells (erythrocytes). Folic acid, formerly known as vitamin B9 or B11, is converted by the body into its active and useful form with the help of vitamin B12. Accordingly, a vitamin B12 deficiency results in a folic acid deficiency. A folic acid deficiency can lead to anemia and the risk of cardiovascular disease increases. However, like most things, too much folic acid is dangerous for the body and can lead to a vitamin B12 deficiency. The two substances are therefore closely related.
  • Nerve protection and regeneration: Since vitamin B12 is responsible for the production of the myelin sheath, a membrane that surrounds nerve cells, it is often referred to as the nerve vitamin. Myelin protects cells and helps transmit signals from cell to cell.
  • DNA formation / cell division: Vitamin B12 is involved in the formation of DNA and cell division. As a result, it stimulates the production of red blood cells and is therefore also heavily involved in blood formation.
  • Breakdown of fatty acids: Vitamin B12 acts as a so-called coenzyme in the breakdown of fatty acids and amino acids. In this function, it helps with the conversion and transfer of metabolic products and is therefore significantly involved in the generation of energy from nutrients.
  • Synthesis of messenger substances: Vitamin B12 plays a role in the synthesis of important messenger substances in the brain. It maintains mood, cognitive performance, memory, perception, coordination, and many other fundamental brain processes. Vitamin B12 is therefore considered to be one of the most important vitamins for the psyche.
  • Detoxification: Numerous studies point to new antioxidant and anti-inflammatory effects as well as immune modulation of vitamin B12. Vitamin B12 is a powerful antioxidant, reduces systemic inflammation and can also be used for detoxification. For example, one study has shown that vitamin B12 neutralizes superoxide radicals and is almost as effective as superoxide dismutase, the body's most powerful antioxidant. (4)

What is the daily requirement of vitamin B12?

As already mentioned, the supply of vitamin B12 is essential for human survival and can only be obtained through food. The daily requirement of vitamin B12 is a value that cannot be determined scientifically and is therefore dependent on various factors. This explains why slightly different values ​​for the daily requirement of vitamin B12 are given internationally. The following table provides information about the recommended daily dose of the German Society for Nutrition (DGE) (5), the EU (6) and the USA (7). The WHO/FAO has also published corresponding values ​​that correspond to those of the USA. (8th)

Adults (over 14 years) 3.0 2.5 2.4 2.4
Pregnant women 3.5 2.6 2.6
breastfeeding women 4.0 2.8 2.8
Children 1-4 1.0 0.9 0.9
children 4-7 1.5 1.2 1.2
children 7-10 1.8 1.8 1.8
Children 10-13 2.0 1.8 1.8

Did you know that it is almost impossible to overdose on vitamin B12 naturally? Since vitamin B12 is one of the water-soluble vitamins, excess vitamin B12 is normally excreted through the kidneys and urine. Only if high-dose vitamin B12 preparations are taken over a long period of time can an overdose put a strain on the kidneys.

How is vitamin B12 absorbed?

Since vitamin B12 is ingested through food, it first reaches the stomach. There it is released by the stomach acid and bound to certain proteins. In the intestine, the small intestinal mucosa can then absorb the vitamin and pass it on to the blood. Transport proteins then carry vitamin B12 to all cells in the body and to the liver.

In order for the absorption of vitamin B12 in the body to run smoothly, the stomach, pancreas and intestines have to work properly. If the function of one of these organs is disturbed or if there are too few transport proteins, this can lead to a vitamin B-12 deficiency. (9)

What are the causes of vitamin B12 deficiency?

Since vitamin B12 cannot be produced by the body itself, a common cause is a lack of vitamin B12 in the diet. But other causes can also be responsible for the deficiency.

Vegetarian or vegan diet

A vegan or vegetarian diet is a common cause of vitamin B12 deficiency. Since vitamin B12 is found almost exclusively in animal foods, vegans can only get enough of this vitamin through dietary supplements. Vegetarians are also often dependent on food supplements to cover their daily requirements, since products such as cheese, milk and eggs have significantly lower vitamin B12 levels than meat and fish.

Plate full of vegetables

A purely plant-based diet provides the body with almost no vitamin B12, which is why it has to be supplied to the body via dietary supplements. (Source: Anna Pelzer /

Some studies are currently dealing with the issue of whether the body can also be supplied with sufficient vitamin B12 via algae or fermented foods. One of these studies confirms that although seaweed would provide enough vitamin B12 in sufficiently large amounts, this does not come close to the average consumption of a vegan and thus cannot provide enough vitamin B12. (10)

The difference in diet between the sexes can also be an indication of why more women suffer from vitamin B12 deficiency. According to a study by the American Society for Microbiology, men consume more animal products. (11)

high age

Age is another risk factor for vitamin B12 deficiency. According to a study, around 10-15% of people over the age of 60 are affected by a vitamin B12 deficiency. (12)

The reasons for this are that older people suffer from chronic diseases more often than average, take various medications and have changed eating habits in old age. In addition, older people produce less stomach acid. However, this is necessary to release vitamin B12 from food so that it can later be absorbed into the blood. (12)

pregnancy and breastfeeding

Since pregnant and breastfeeding women not only have to provide themselves but also their children with vitamin B12, they have an increased need for vitamin B12 (see table under daily requirement).

An undersupply should be avoided as far as possible, since vitamin B12 plays a significant role in the physical and mental development of the child.

Studies show, for example, that a vitamin B12 deficiency as a result of an unbalanced diet is passed on from mother to child. This deficiency results in vomiting, lethargy, failure to thrive, hypotonia, and stagnation or regression of developmental skills in the infant's first months of life.

Early diagnosis of vitamin B12 deficiency is therefore essential, especially in the context of maternal nutritional deficiencies. Only in this way, for example, is a complete neurological recovery possible. (13)

diseases and operations

There are some diseases that inhibit or prevent the absorption of vitamin B12 and are therefore possible causes of vitamin B12 deficiency.

  • Gastritis: This is an inflammation of the gastric mucosa. The disease results in low acid release from the gastric mucosa, which in turn leads to reduced release of free vitamin B12 from dietary proteins. (12)
  • Damage to the mucous membrane of the small intestine : Diseases such as Crohn's disease, which belong to the group of chronic inflammatory bowel diseases, lead to inflammation in the intestinal tract and therefore also affect vitamin B12 absorption.
  • Pancreatitis : In this disease, the pancreas is inflamed. This leads to a lack of the enzyme trypsin, which is needed for the absorption of vitamin B12. (14)

What is the connection between vitamin B12 deficiency and weight gain?

Basically, there is no direct connection between vitamin B12 deficiency and weight gain.

So it cannot be said that vitamin B12 deficiency leads to weight gain.

What may well be, however, is that vitamin B12 deficiency is the result of another disease that also has weight gain as a symptom. An autoimmune inflammation of the thyroid gland, for example, manifests itself in symptoms such as weight gain, tiredness and exhaustion, but also in pernicious anemia (anemia) and, in this connection, also with a vitamin B12 deficiency. (15)

Since vitamin B12 deficiency leads to tiredness, rapid exhaustion and a generally low mental resilience, the weight gain can also be due to a lack of exercise and unhealthy eating as a reaction to the increased stress level.

Which foods contain vitamin B12?

Since only certain microorganisms are able to form vitamin B12, humans have to absorb the vitamin through food. Animal foods such as meat, fish, eggs and milk in particular contain a lot of vitamin B12. Vegetable food provides almost no vitamin B12. An exception is sauerkraut, which contains vitamin B12 after bacterial fermentation.

The amounts of vitamin B12 found in nori seaweed are too low and not everyone can absorb this form of the vitamin. Accordingly, vegans and vegetarians are forced to take dietary supplements to meet their vitamin B12 needs.

The following table provides an overview of which foods contain how much vitamin B12 (per 100 grams). (16)

meat and fish Vitamin B12 content Vegetarian Food Vitamin B12 content
beef liver 91 µg Emmental 3.1 µg
calf liver 60 µg Camembert 2.6 µg
pork liver 39 µg Edam 1.9 µg
bovine kidney 33 µg cottage cheese 2.0 µg
mackerel 9 µg chicken egg 1.9 µg
herring 8.5 µg curd 0.8 µg
Salmon 4.7 µg whole milk 0.4 µg
tuna 4.3 µg cream 0.4 µg
lamb meat 2.7 µg yoghurt 0.4 µg

About two to five micrograms of vitamin B12 are stored in the body. Half of it is in the liver and can remain there for almost three years. (3) It is therefore not surprising that the foods with the highest levels of vitamin B12 are animal livers.

different kinds of meat

Vitamin B12 is found almost exclusively in animal products such as meat. Fish, eggs and quark are also vitamin B12 suppliers for the human body. (Source: Free-Photos /

What are the symptoms of vitamin B12 deficiency?

Vitamin B12 deficiency manifests itself in many different ways. The question of weight gain as a result of vitamin B12 deficiency is not directly linked to the vitamin deficiency, rather both show up as symptoms of another disease. Typical symptoms of vitamin B12 deficiency are discussed below.

fatigue and exhaustion

Since vitamin B12 is involved in numerous metabolic processes in the body, it is also responsible for our energy balance. Accordingly, a vitamin B12 deficiency impairs your mental and physical performance. You feel tired and listless. This also includes headaches and difficulty concentrating.


One of the functions of vitamin B12 is its participation in cell division. In the case of a vitamin B12 deficiency, cell division in the bone marrow is disturbed because the body has too little vitamin B12 available for this important task. Accordingly, fewer red blood cells are formed. The result is pernicious anemia, a special form of anemia.

Here, too, the symptoms are tiredness, reduced performance and difficulty concentrating. (17)

Neurological symptoms / depression

In addition to cell division, the protection of nerve cells is also an important task of vitamin B12. If there is a deficiency, the vitamin or the body cannot fulfill this task and fewer nerve fibers are formed in the spinal cord. (18)

Scientists are still researching the exact connections between vitamin B12, folic acid and depression.

As a result, neurological symptoms such as nervousness, irritability, a numb feeling / pins and needles in the hands, arms, feet and legs or depression occur. One of the common theories goes back to the amino acid homocysteine. As a result of a vitamin B12 deficiency, the level of homocysteine ​​in the body is too high. This excess of the amino acid can damage brain tissue and interfere with signal transmission. This, in turn, can lead to mood swings and depression. (19)

weight gain

Weight gain is not a typical symptom of vitamin B12 deficiency. It is much more the result of diseases that also result in vitamin B12 deficiency. Therefore, vitamin B12 deficiency and weight gain may occur at the same time, but not as a cause and effect, but both as a consequence of a disease.

What diseases are associated with vitamin B12 deficiency?

As already mentioned, vitamin B12 deficiency is closely linked to problems and irritation in the gastrointestinal tract, leading to impaired absorption. Autoimmune reactions against the vitamin B12 transport molecules can also be a reason for this. Older people are more affected by vitamin B12 deficiency because the general absorption capacity decreases with age.

The most common diseases associated with vitamin B12 deficiency or absorption disorders are the following:

  • Inflammation, irritation and diseases of the stomach and intestines
  • Autoimmune reactions against the vitamin B12 transport molecules
  • gastritis
  • Crohn's disease
  • Infection with parasites such as Helicobacter pylori or tapeworms
  • liver damage
  • Damage to the pancreas
  • bowel resection

Can the human body produce vitamin B12 itself?

The formation of vitamin B12 by the human body is not possible and can only be supplied from the outside.

Vitamin B12 Deficiency: 3 Effective Approaches to Treatment and Prevention

Since the cause of vitamin B12 deficiency can have different causes, the treatment must also be differentiated between treatments that correct the deficiency or the cause. Both approaches are discussed below.

Take preparations & dietary supplements

Since vitamin B12 cannot be produced by the body and is mainly found in animal foods, taking the vitamin from preparations and dietary supplements is an option for many. Supplementation is vital for vegans in particular, but also for vegetarians, since vitamin B12 is almost non-existent in their food.

The dietary supplements are usually available in the form of capsules or drops and are often vegan. The dosage of these preparations varies greatly. According to some studies, short-term doses of 500 to 2,000 micrograms a day can be useful to compensate for a deficiency. The dose should then be reduced for long-term use. (20)

As an alternative to capsules and drops, vitamin B12 can also be injected into the muscle. These injections are very high doses and are usually given by doctors to quickly replenish depleted vitamin B12 stores.

change nourishment

As mentioned above, vitamin B12 is almost exclusively ingested through animal foods. Means meat, fish, eggs and dairy products. For vegans and vegetarians, a change in diet would mean going back to consuming animal products. Consuming fish, called pescetarians, might be a viable option for some of you.

Even people who do not consciously see themselves as vegans or vegetarians can increase their vitamin B12 intake by eating more meat.

If you follow a vegan diet and don't want to change it, you won't be able to avoid taking vitamin B12 through dietary supplements.

treatment with medication

The cause of the vitamin B12 deficiency should be clarified in any case in order to determine the right treatment. Treatment with medication makes sense if the vitamin B12 deficiency is due to a disease-related cause.

Since vitamin B12 deficiency is linked to many diseases in the gastrointestinal tract, only an expert can make an accurate diagnosis and suggest appropriate treatment. Be sure to consult your doctor if you feel that your vitamin B12 deficiency is not related to diet, which you could easily correct with other eating habits or supplements.


A vitamin B12 deficiency can have unpleasant consequences. The treacherous thing is that the deficiency is often not noticed because the body stores vitamin B12 and the deficiency is only noticed after these stores have been used up.

Vitamin B12 deficiency can be caused by an unbalanced diet, a vegan/vegetarian diet and diseases. Consequences are tiredness, exhaustion, anemia as well as neurological symptoms and depression. Weight gain is not a direct result of vitamin B12 deficiency.

Since vitamin B12 performs many important tasks in the body, such as protecting the nerves or cell division, the vitamin is vital for humans. Failure to diagnose or treat in time can result in irreparable damage. Neurological functions in newborns, for example, are particularly affected, as vitamin B12 is responsible for the development of the brain and nerves.

You can easily get a handle on the treatment of a vitamin B12 deficiency due to diet with a change in diet or dietary supplements. In the case of vitamin B12 deficiency as a result of a disease in the gastrointestinal tract, the treatment of the cause is more extensive and must be discussed with a trusted doctor. Unlike deficiency, overdose is largely harmless to adults.

h2>Individual proofs
  1. Institute of Medicine (US) Standing Committee on the Scientific Evaluation of Dietary Reference Intakes and its Panel on Folate, Other B Vitamins, and Choline. Estimation of the Period Covered by Vitamin B12 Stores. National Academies Press (US), 1998.
  2. W. Kaim, B. Schwedersk, Bioinorganic Chemistry - On the function of chemical elements in life processes., 4th edition. Teubner, 2005.
  3. H. Kasper and W. Burghardt, Nutritional Medicine and Dietetics, 12th, revised. Edition Munich: Elsevier, Urban & Fischer, 2014.
  4. Suarez-Moreira E, Yun J, Birch CS, Williams JHH, McCaddon A, Brasch NE (2009) Vitamin B 12 and Redox Homeostasis: Cob(II)alamin Reacts with Superoxide at Rates Approaching Superoxide Dismutase (SOD). Journal of the American Chemical Society 131:15078-15079
  5. German Society for Nutrition, Austrian Society for Nutrition, Swiss Society for Nutrition Research, Swiss Association for Nutrition (ed.) "Reference values ​​for nutrient intake" 1st edition, 5th, corrected reprint, DGE, Bonn 2013
  6. Commission Directive 2008/100/EC of 28 October 2008 amending Council Directive 90/496/EEC on the nutritional labeling of foods with regard to recommended daily doses, energy value conversion factors and definitions
  7. Subcommittee on the Tenth Edition of the RDAs, Food and Nutrition Board, Commission on Life Sciences, National Research Council: Recommended Dietary Allowances: 10th Edition. National Academy Press, Washington, DC, 1989
  8. World Health Organization, Food and Agricultural Organization of the United Nations "Vitamin and mineral requirements in human nutrition", Second edition, WHO, 2005.
  9. D. Ä. G. Ärzteblatt Editors German, "Causes and early diagnosis of vitamin B12 deficiency", 03-Oct-2008. [On-line]. Available at: [Accessed: 26-July-2020].
  10. Anna-Liisa Rauma, Riitta Törrönen, Osmo Hänninen, Hannu Mykkänen, Vitamin B-12 Status of Long-Term Adherents of a Strict Uncooked Vegan Diet (“Living Food Diet”) Is Compromised, The Journal of Nutrition, Volume 125, Issue 10 , October 1995, pages 2511-2515,
  11. American Society for Microbiology. [On-line]. Available at: [Accessed: 27-July-2020].
  12. Baik, HW, & Russell, RM (1999). Vitamin B12 deficiency in the elderly. Annual review of nutrition, 19, 357-377.
  13. Bousselamti, A., El Hasbaoui, B., Echahdi, H., & Krouile, Y. (2018). Psychomotor regression due to vitamin B12 deficiency. The Pan African medical journal, 30, 152.
  14. Editors of Deutsches Ärzteblatt, “Vitamin B12 deficiency due to metformin”, May 21, 2010. [On-line]. Available at: [Accessed: 27-July-2020].
  15. Monika Hortig (2020), Vitamin B12 deficiency and its symptoms, Available at: [Accessed: 27-July-2020].
  16. German Green Cross for Health eV, "Occurrence of vitamin B12", German Green Cross for Health eV [Online]. Available at: [Accessed: 26-July-2020].
  17. Symptoms”,, 20-Oct-2017. [On-line]. Available at: [Accessed: 11-July-2020].
  18. National Institutes of Health, Office of Dietary Supplements - Vitamin B12. [On-line]. Available at: [Accessed: 27-July-2020].
  19. P Bhatia and N Singh, Homocysteine ​​excess: delineating the possible mechanism of neurotoxicity and depression, Fundamental & Clinical Pharmacology, Vol 29, No 6, pp 522-528, 2015.
  20. CC Butler et al., "Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency: a systematic review of randomized controlled trials", Fam Pract, vol. 23, no. 3, pp. 279-285, June 2006.
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