We are currently seeing a fundamental shift in attitudes towards vegetarian and vegan lifestyles. More and more people are choosing not to eat animal products – for any number of reasons. While opponents and supporters of a purely plant-based diet continue to battle it out amongst themselves, one thing is becoming increasingly clear: other food trends may come and go, but this development is here to stay. What is more, it is constantly picking up speed and gaining new followers. If you do opt for a purely plant-based diet, however, you need to pay particular attention to one vitamin for the sake of your health: the B vitamin “B12”.
What is vitamin B12?
Vitamin B12 (also known as “cobalamin”) is not an isolated substance but a collective term for several compounds that all have one and the same effect. Also called the “red vitamin” because of its color, B12 was the last of the currently known vitamins to be discovered (in 1926). But this does not make the water-soluble nutrient any less important for human health.
Vitamin B12 acts as a coenzyme in the human body: it helps enzymes do their job. Vitamin B12 thus not only makes an important contribution to cell division, but is also a key factor in energy metabolism, immune defense and healthy homocysteine metabolism. It also helps maintain healthy neural and mental function and is involved in the formation of red blood cells.
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.
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 (non-pasteurized) 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.
Vegans are frequently called upon to keep an eye on their vitamin B12 supply, but vegetarians should be aware their vitamin B12 status as well. Irrespective of diet, there are other groups who also need to watch their B12 levels. These include pregnant and breastfeeding women, the elderly, and people who are prone to disorders of the gastrointestinal tract.
However, an adequate intake of vitamin B12 is not enough to ensure a healthy supply – our body must also be able to utilize the vitamin B12 we ingest. Active absorption of B12 in the small intestine is only possible after it has been detached from the food we eat and bound to a transport protein (this is known as the intrinsic factor and is produced in the cells of the stomach lining). Higher doses of this water-soluble vitamin (e.g. via vitamin B12 supplements) can also be absorbed passively via the intestinal mucosa.
What is a good source of vitamin B12 for vegans and vegetarians?
While ovo-lacto vegetarians can maintain their vitamin B12 balance by consuming animal products such as eggs and dairy products, vegans, lacto-vegetarians and raw foodists may need to pay extra attention to their vitamin B12 intake. In addition to specially fortified foods, vitamin B12 supplements containing the vitamin in natural, utilizable forms can help ensure a healthy daily supply.
If you‘re looking for purely plant-based sources, chlorella is an option. Unlike other types of algae, chlorella contains mainly utilizable vitamin B12 and hardly any B12 analogues. Despite this, chlorella algae are not recommended as the sole source of B12 in a purely plant-based diet since their B12 content is relatively low.
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.
The best products for replenishing vitamin B12 stores are those that contain B12 in near-natural, utilizable forms. These include methylcobalamin and adenosylcobalamin, as well as hydroxycobalamin, which can be stored very effectively in the body. If you try to hack a path through the jungle of dietary supplements, you will notice that vitamin B12 preparations are available on the market in an enormous variety of dosages. While 1 µg of vitamin B12 is absorbed actively without involving passive diffusion, a 1000 µg dose of vitamin B12 is absorbed almost exclusively passively. In this case, however, only a fraction of the ingested amount is actually absorbed into the body (~ 10 µg).
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.