Vitamin B12 – effect, occurrence, daily requirement & values

Vitamin B₁₂, also known as cobalamin, is a water-soluble vitamin that is essential for various vital functions in the body. Because of its colour – it is also known as the “red vitamin” – B₁₂was the last of the vitamins known today to be discovered (1926). However, this does not make the water-soluble nutrient less important for us humans.

It plays a central role in cell division and in the functioning of the nervous system and it is indispensable for the formation of blood cells, especially red blood cells.

However, this essential vitamin is found almost exclusively in foods of animal origin such as meat, fish, eggs and dairy products. People who eat vegan foods therefore have an increased risk of developing vitamin B₁₂ deficiency because this nutrient is hardly ever present in plant-based foods. People who eat a lacto-vegetarian diet, i.e. do not eat meat, fish or eggs, also potentially absorb less vitamin B₁₂, especially if dairy products are only on the menu to a very limited degree.

Vitamin B₁₂ is an essential vitamin involved in blood formation and cell division. It also contributes to normal homocysteine metabolism, immune function, energy metabolism, and normal mental functions.

Vitamin B12 is an exceptional case among vitamins, because appreciable amounts of it occur only in animal products. Cobalamins are produced by microorganisms and enter the animal organism via various routes. While meat-eating animals are like humans and take in nutrients from their animal prey, herbivores harbor special colonies of bacteria in their digestive tract and/or meet their needs by consuming “dirt”, i.e. soil and microorganisms. Fish are another good source of B12 and generally absorb the essential nutrient via plankton in the water or produce it themselves with the aid of their intestinal flora.

As mentioned above, vitamin B12 is only found in sufficiently high quantities in animal products. If you eat meat, fish, eggs, offal and dairy products, it is generally quite easy to cover your daily requirements. Most plant-based foods do not contain vitamin B12. There are some exceptions, such as fermented foods like sauerkraut, kimchi, pickled vegetables, and beer, and foods contaminated by bacteria (e.g. tuber and root vegetables), which may contain traces of various types of B12. Under certain circumstances, however, these compounds are present in a form that our body is unable to process ( “vitamin B12 analogues”) and whose presence may even impede the utilization of useful forms of vitamin B12.

Our body does not need large amounts of vitamin B12. According to the German Society for Nutrition (Deutsche Gesellschaft für Ernährung or DGE), just 4 µg a day is sufficient to maintain the vitamin B12 balance in the human body. As is often the case, however, pregnancy and breastfeeding represent exceptions to the rule. The B12 needs of pregnant and breastfeeding women increase to 4.5 µg and 5.5 µg per day. The human organism maintains vitamin B12 stores for times of scarcity. Replete B12 stores contain about a thousand times the amount (4 g) of our daily B12 requirements. However, a constant lack of B12 will deplete these stores in the long run.

A vitamin B-12 level test generally involves measuring the total amount of vitamin B12 in the blood. However, it can take a relatively long time for this value to register a B12 deficiency. Supplies of vitamin B12 may already be low even if the total vitamin B12 value is still within the normal range. Ideally, therefore, other values should also be used. Holotranscobalamin (holoTC), also known as “active B12”, is a laboratory value that indicates a lack of vitamin B12 at an early stage. Low holoTC values indicate a depletion of the B12 stores or a negative B12 balance. Methylmalonic acid (MMA) values can also tell us a lot about our B12 status. In this case, higher values are a sign of empty B12 stores.

When it comes to monitoring the vitamin B₁₂ supply, vegans are often put in the spotlight – but ideally vegetarians should also be aware of their vitamin B₁₂ status. Irrespective of diet, there are other groups that should be aware of their B₁₂ levels. These include pregnant and breastfeeding women, elderly people and people who have more frequent problems with their gastrointestinal tract.

However, a sufficient intake of vitamin B₁₂ is not enough for a good supply status – our body must also be able to use the vitamin B₁₂ that is consumed. Only the extraction from food and the binding to a transport protein (= “intrinsic factor”, which is formed in the cells of the gastric mucosa), allows active B₁₂ uptake in the small intestine. In higher doses (e.g. using vitamin B₁₂ supplements), the water-soluble vitamin can also be passively absorbed via the intestinal mucosa.

Water-soluble vitamin B₁₂ is essential for our health. However, it can be a challenge for vegans to consume enough vitamin B₁₂ through food, as it is mainly found in foods of animal origin. Therefore, people on a vegetarian and vegan diet are advised to consume vitamin B₁₂ supplements or enriched foods to an appropriate extent. It is also important to ensure that the need for iodine, calcium, vitamin D, iron, omega 3 fatty acids and protein is met through food, so in-depth nutritional knowledge is the key requirement for a healthy vegan diet.

When should you take vitamin B₁₂?

In order to improve vitamin B₁₂ absorption via the intrinsic factors formed in the stomach lining, the water-soluble vitamin B12 should ideally be taken on an empty stomach or between meals.

What is the best way to absorb vitamin B₁₂ into the body?

People who eat omnivorous diet, i.e. who also eat animal foods, should not have any problems meeting their vitamin B₁₂ needs through food. Most vitamin B₁₂ is found in animal foods such as meat, offal, fish and dairy products.

What is the best way to take Vitamin B12?

As already mentioned, Vitamin B₁₂ is best taken on an empty stomach or between meals. However, the absorption capacity of the intrinsic factor is limited, and this active absorption pathway can be impaired by several factors. Larger amounts of vitamin B₁₂ can also be absorbed without transporters (passive diffusion) via the mucous membranes of the digestive tract.

Vitamin B₁₂ and folic acid are team players. They work closely together as an integral part of our metabolism, contributing to homocysteine metabolism and playing an important role in blood formation.* In addition, these two water-soluble B vitamins are also important for a healthy functioning nervous system.

* Vitamin B₁₂ plays an important part in the normal formation of red blood cells; folic acid contributes to normal blood formation.