Nutrition is always subject to ongoing trends as people around us try new and promising diets. Although some people may have adopted “veganism” or “vegetarianism” for reasons of sustainability, for most people, these are just keywords that are gaining popularity. Vitamin B12 is a related topic that is trending, although shadowed by semi-truths. While many underestimate the role of this water-soluble vitamin contained in foods from animal sources, this post sets out to answer some questions about veganism and B12 deficiency.
1. What is vitamin B12?
Vitamins are organic compounds needed for the sustenance of life (Lat. vita=life).
Vitamin B is a group of 8 different nutrients – Vitamins B1, B2, B3, B5, B6, B7/biotin, B9/folic acid and B12.
They are collectively known as the vitamin B complex because it is often supplied as a vitamin cocktail. In particular, vitamin B12 also known as cobalamin (cobalt-containing vitamin), exists naturally as different sub-variants. All of these variants are collectively necessary for various processes such as haematopoiesis, development and function of the nervous system and metabolism.
Some important facts about the vitamin:
- B12 is part of the vitamin B complex, the B group consisting of 8 different components (B1, B2, B3, B5, B6, biotin, folic acid and B12)
- Its chemical name is cobalamin, as it is the only organic molecule that contains cobalt.
- There are several forms of B12: methylcobalamin and 5-deoxyadenosylcobalamin are active in the human body
- The liver can serve as a vitamin B12 reservoir for several years
2. What foods contain vitamin B12?
Vitamin B12 is produced by certain microorganisms in the gastrointestinal tract of animals and is thus concentrated only in products of animal origin. Most of this essential nutrient is stored in the liver of these animals.
|Vitamin B12 foods||Micrograms of B12 per 100 grams|
|Cow's milk (1.5 - 3.5% fat)||0.4|
|Crispy fresh cheese||1|
|Fish, marine animals|
|Meat, poultry, sausage|
|Leg of lamb (raw)||3,6|
|Alcohol-free beer, malt beer||0.1|
|Wheat / white beer||0.1|
As can be seen from the table, the daily recommended intake of vitamin B12 (2,4 ug/day) cannot be met even in those who consume a meat-based diet. As can also be seen in the table, higher plants cannot concentrate vitamin B12 from soil and water and are thus a poor source of the vitamin. Further, it must be remembered that 100% of the vitamin contained in the food cannot be absorbed by the body. Fortunately, though, our livers store a vast amount of vitamin B12, of which only 0.1-0.2% is lost per day. Thus, only supplementation of our daily diets is necessary.
3. How do we obtain vitamin B12 from food?
The vitamin B12 that is found in the food we eat is usually bound to other proteins in the food and must first be released from them. This is done by cooking the food or by the salivary and stomach acids and enzymes (pepsin) upon ingestion.
The free vitamin B12 now binds to another protein, haptocorrin, for further transport. Once in the small intestine, this compound is degraded by pancreatic enzymes (proteases). The free vitamin B12 then binds to yet another helper protein, the intrinsic factor. The vitamin B12-intrinsic factor complex is carried to its site of absorption in the small intestine. It is only this specific complex that binds to the membrane receptors on the intestinal cells. B12 analogues or vitamin B12 bound by any other factor, do not get absorbed. Vitamin B12 then enters circulation where it is bound to transcobalamin II (TC II), essential for its correct absorption by the other tissues of the body. Once the vitamin has reached its target tissue, it is separated from TC II and transformed into methylcobalamin or adenosylcobalamin which are important enzyme cofactors in processes such as DNA synthesis.
Image from Langan RC and Goodbred AJ. Am Fam Physician. 2017 Sep 15;96(6):384-389
The majority of vitamin B12 is absorbed and stored in the liver, kidney and bone marrow. The vitamin in these “stores” can be broken down and used over several years. One must, therefore, make sure to replenish these stores regularly in order to prevent a vitamin B12 deficiency. We, humans, produce vitamin B12 with the help of microorganisms in the large intestine (the colon). However, as most of the nutrient absorption occurs in the small intestine, upstream of the colon, most of this naturally synthesised nutrient is lost. We must therefore, replenish our stores of vitamin B12 from dietary sources.
4. Why is the storage of vitamin B12 important?
The B12 stores in the liver are a source of a steady and sufficient supply of B vitamins into the bloodstream.
With this functionality, the body protects itself from, for example, vitamin B12 deficiency and regulates necessary bodily functions. A sustained source of vitamin B12 can provide many benefits.
Develops red blood cells
Along with vitamins B6 and B9 (folic acid), vitamin B12 plays a crucial role in the formation of new red blood cells, including in DNA synthesis and haemoglobin production. Vitamin B12 deficiency thus, leads to underdeveloped red blood cells and reduces their oxygen carrying capacity. The metabolic functions of the body are, therefore, impaired.
Supports nerve function
Vitamin B12 is necessary for the synthesis of myelin, the biological membranes that sheath some of our nerve fibres and that help in rapid communication between neurons. This vitamin therefore, contributes to the normal functioning of the nervous system. Studies also show that for the proper development of the nervous system of a foetus, sufficient B12 levels in the mother are necessary . The foetus is particularly sensitive at the beginning of pregnancy, during the active phase of neural tube development. A vitamin B12 deficiency at this time, it is said, can increase the risk of neural tube defects.
A pregnant woman with a vitamin B12 deficiency is also less likely to carry the baby to term. One study found that women with vitamin B12 levels of less than 250 mg/dL (milligrams per deciliter) are three times more likely to give birth to a baby with birth defects than women with recommended levels . Women with a vitamin B12 deficiency and B12 levels below 150 mg/dL were five times more likely to have a child with birth defects compared to women with B12 levels above 400 mg/dL .
Helps with energy production
Catabolism is the metabolic process of breaking down molecules to obtain energy and this is the process by which we obtain energy from the food we consume. Vitamin B12 is particularly important for this process as it contributes to the breakdown of fatty acids and amino acids. A deficiency of vitamin B12 can impair the body’s energy production. It can also impair the body’s ability to produce glucose from non-carbohydrate sources especially during fasting.
Helps keep our ageing populations healthy
As vitamin B12 is important for many of important processes outlined above, its deficiency in an ageing population has been shown to be associated with a loss of vision, diminished strength and possibly cognitive decline.
5. How do I recognize a vitamin B12 deficiency?
The daily requirement of 2,4 ug of vitamin B12 can often not be covered through a normal diet.
However, since the liver stores several milligrams of the vitamin and uses only 0.1-0.2% of its stores per day, a diet comprising of animal-based products is often enough to restore the balance. If, however, there is a deficiency, it indicates that the body has used up its vitamin B12 stores.
This loss should be replenished as quickly as possible through the use of high-dose food supplements or injections. In general, a:
- Low intake with an unbalanced or strictly vegetable diet
- Problems with B12 absorption in older adults, people with anaemia, patients with digestive system disorders (Crohn's disease, celiac disease) and after a digestive system surgery (gastric bypass, intestinal removal).
A B12 deficiency can manifest itself in different ways depending on its severity - from mild fatigue to severe neurological impairment and nerve damage. Other deficiency symptoms include: Pernicious anemia and psychiatric disorders such as memory loss, depression, irritability or dementia [2, 3].
Vitamin B12 deficiency is difficult to assess because our liver has a huge storage capacity. Although we only need about 2,4 µg of cobalamin per day, our liver stores between 2,000-4,000 µg. From the time when animal food is renounced, the 4 phases of B12 deficiency  begin, until the reserves in the liver are completely depleted. In the early phases of the deficiency there are no symptoms yet.
As soon as clinical deficiency occurs, however, the condition of the affected person must already be considered critical:
- Decrease of holotranscobalamin (active form of vitamin B12) in the blood
- Decline of cobalamin in cells
- Biochemical deficiency: DNA synthesis slower, more homocysteine and methyl malonate in the blood
- Clinical deficiency: Anemia
Therefore, the rule of thumb is: If you belong to a B12 risk group, you should have your status regularly determined by blood tests. This is the only way to detect the deficiency as early as possible and to easily compensate before symptoms appear!
6. Who belongs to a risk group??
Although anaemia and nerve damage can occur due to a lack of the vitamin, few people know that they too could be in a risk group for serious B12 deficiency, since it takes several years to manifest.
As mentioned several times in this article, ovo-lacto vegetarians and vegans do not meet their daily requirements of vitamin B12 from food. In the long run, this depletes their liver stores.
To prevent a deficiency, those falling under this category should take regular vitamin B12 supplements to replenish their reserves. A regular check of the blood level by a doctor is also important. In older people, the problem of a vitamin B12 deficiency is majorly due to malabsorption. 10-30% of older people secrete less stomach acid . This means that they are no longer able to separate B12 from proteins in their diet. However, absorption of the free form of B12 from food supplements or fortified foods continues to work  and is the only safe source of B12 in older people. Since vitamin B12 reaches the foetus via the placenta during pregnancy, mothers on a vegetarian or vegan diet should take B12 supplements.
Without an adequate supply of B12, severe neurological disorders can occur in the child. This also applies to the breastfeeding period!
Caution with too much folic acid! A high folic acid intake can mask a vitamin B12 deficiency until it leads to serious consequences. Therefore, folic acid intake from fortified foods or food supplements should be limited to 1,000 µg per day .
7. How to replenish a B12 deficiency?
If an acute deficiency exists, B12 injections are usually prescribed. Oral B12 preparations can also be used to compensate for a deficiency.
In the course of a cure to compensate for a deficiency, 2,000 µg daily followed by 1,000 µg daily, then 1,000 µg daily weekly and finally 1,000 µg monthly must be taken . Stores replenished in this way, can then supply the body again with small daily doses of B12 over several months. The regimen should, however, be repeated several times a year, especially for vegans and older people.
- a weekly dose of 2000 µg via food supplement
- OR a dose of 3 µg two to three times per week via fortified food
- OR 10 µg daily via dietary supplement  Is also recommended.
So far, no maximum daily dose has been established, as no side effects of a very high dose of vitamin B12 have been observed .
8. Do vegetarians need vitamin B12 supplements?
Many people who choose a predominantly plant-based or even vegan diet are not aware that they will need to be adequately supplemented with vitamin B12.
This is a major problem since the clinical consequences of B12 deficiency develop years later (a delay in symptoms of up to 10 years, can be expected). However, once the symptoms occur, it is already too late.
A word of caution: The role of the vitamins is sometimes massively downplayed. Plant-based foods such as tempeh or algae themselves cannot be used as alternatives since they do NOT contain biologically active/available vitamin B12. Vitamin B12-fortified foods such as fortified muesli or enriched yeast can be a good alternative for vegetarians and vegans. However, in order to replenish the liver supply, food supplements are generally recommended.
9. Why is liposomal B12 the best supplement?
Studies have shown that only approximately 56% of a 1µg dose of vitamin B12 is absorbed by the small intestine.
To increase the amount of vitamin B12 in circulation, it is usually injected intramuscularly to make up for an acute deficiency. Another option is to take a high amount (more than a 1000 µg/day) orally. Oral supplements of pure/unbound B12 can effectively be absorbed via passive diffusion across the intestinal membrane.
However, since only 3% of this B12 is absorbed by diffusion, a higher dosage is required when taken orally so that the recommended daily intake is met.
Liposomal vitamin B12 supplements are a great option as they are taken orally and are thus non-invasive. Liposomes also protect pH-sensitive compounds, such as vitamin B12, from degradation in the stomach. Further, a study in a Greek population indicated that in a group of men and women of approximately 60 years of age, sub-lingual liposomal B12 supplements (1000 µg/day) resulted in an increase in circulating vitamin B12 levels by 55% after 1 week, 105% after 1 month and 270% after 2 months of daily supplementation .
You can find out more about liposomes and how they revolutionise our nutrition and the supplement market.
 Lee GR. Pernicious anemia and other causes of vitamin B12 (cobalamin) deficiency. In: Lee GR, et al., eds. Wintrobe's Clinical hematology. 10th ed. Baltimore: Williams & Wilkins, 1999:941–64.
 Lindenbaum J, Healton EB, Savage DG, Brust JC, Garrett TJ, Podell ER, et al. Neuropsychiatric disorders caused by cobalamin deficiency in the absence of anemia or macrocytosis. N Engl J Med. 1988;318:1720–8.
 V Herbert, Staging vitamin B−12 (cobalamin) status in vegetarians, The American Journal of Clinical Nutrition, Volume 59, Issue 5, May 1994, Pages 1213S–1222S, https://doi.org/10.1093/ajcn/59.5.1213S.
 Stephen Walsh and other members from the International Vegetarian Union science group (IVU-SCI) (2001): What Every Vegan Should Know about Vitamin B12: An Open Letter from Health Professionals and Vegan Organizations; https://veganhealth.org/explanation-of-vitamin-b12-recommendations/
 Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academy Press, 1998.
 Carmel R. How I treat cobalamin (vitamin B12) deficiency. Blood.2008;112:2214-21.
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 Katsogiannis I, Fikioris N, Kontogiorgis C, Constantinides T (2018) Evaluation of liposomal B12 supplementation in a case series study. Glob Drugs Therap 3: DOI: 10.15761/GDT.1000160