Vitamin B12 is an essential vitamin: it's vital for us and must come from food, because our body can't produce it itself.
Most people have heard of vitamin B12. Isn't that what vegetarians and vegans have to take as tablets? Do you need it if you eat a lot of fruit? After all, fruit contains all the vitamins – or does it?
What is vitamin B12?
Vitamin B12 is an essential vitamin, which means it's vital for us and must come from food, because our body can't produce it itself.
Vitamin B12 is stored in the liver, so the body can compensate well for a temporarily insufficient intake. But once the stores are used up and not enough vitamin B12 is supplied, deficiency symptoms appear.
Vitamin B12 is important for many processes in the body. For example, it's involved in forming red blood cells and forming the genetic material DNA and RNA (and therefore in cell division and growth). It also supports the uptake of folic acid into the cells.
Which foods contain vitamin B12?
Vitamin B12 is found mainly in animal foods such as meat, fish, eggs and cheese. The vegetarian foods richest in vitamin B12 are:
- Camembert – 3.1 µg/100 g
- Emmental – 3.1 µg/100 g
- Edam – 2.0 µg/100 g
- Egg yolk – 2.0 µg/100 g
Herbivores take in vitamin B12 through soil and faeces contaminating their food. Carnivores get vitamin B12 from the meat of their prey. In today's factory farming, however, animals hardly see daylight, let alone a pasture. Natural feeding is barely possible, so animal feed is often fortified with vitamin B12. This means people who eat meat and fish also take in extra vitamin B12 indirectly.
In both animals and humans, vitamin B12 is produced by microorganisms in the gut – but only in the large intestine, i.e. after the point of absorption in the small intestine. Most of this vitamin B12 is then excreted with the faeces, which is why the body usually can't absorb the B12 it produces itself.
The only reliable plant source of vitamin B12 is the alga chlorella, with 80 µg per 100 g. That beats all animal foods, but you usually only take in very small amounts per serving. So as the only source of vitamin B12 it's usually not enough.
Who should take extra vitamin B12?
Vegetarians, who eat no meat, and vegans, who eat no animal foods, should therefore supplement vitamin B12. Because our food is processed hygienically, it no longer carries contamination such as dirt or faeces, so vegetables and the like no longer provide vitamin B12.
But extra intake can also be beneficial for people who eat meat. Vitamin B12 is sensitive to heat, so some of it is lost during cooking. Meat is also harder to digest than cheese and fish. Put simply, vitamin B12 attaches to proteins – the more easily they're digested, the better the vitamin B12 can be absorbed.
How much vitamin B12 should I take?
According to the German Nutrition Society (DGE), an adult's daily requirement is 3 µg. Current studies, however, point to a requirement of 7–10 µg.
People who smoke, drink a lot of alcohol or have a gastrointestinal disease usually need more. According to the DGE, pregnant and breastfeeding women also need at least 3.5 µg and 4 µg a day respectively.
Since only very small amounts of the vitamin B12 you take in can be absorbed, oral supplements are usually very highly dosed. Because excess B12 is simply excreted in the urine, no overdoses are known and the DGE has set no upper limit for daily intake. Still, you should treat your body with care.
What happens with a vitamin B12 deficiency?
With insufficient vitamin B12 intake, the body's stores are depleted first, usually with only mild symptoms. Once the stores are empty, however, severe symptoms appear.
- Mild symptoms: tiredness, susceptibility to infections, mood swings
- With empty stores: digestive problems, coordination problems, tingling in the limbs, anaemia, nerve damage
If you have such complaints, you should definitely see a doctor and have your B12 level tested.
