Vitamin B12 is almost exclusively found in animal-based foods. That’s why vegetarians and vegans are a risk group. A blood test can show whether you have a deficiency. It is treated with a course of tablets or injections.
Vitamin B12 is also known as cobalamin. Compared to other vitamins, the human body only needs very little vitamin B12 as it is good at storing it.
The body needs vitamin B12 for several reasons, including to renew cells, form blood and to keep the nervous system working properly. It also plays an important role in energy metabolism. As the body can’t make vitamin B12 itself, it needs to get it from food.
Vitamin B12 is almost exclusively found in animal sources like meat, fish and dairy products. These foods are rich in vitamin B12 (values in micrograms per 100 g):
Researchers have found that mushrooms, algae, fermented soybeans and leafy vegetables contain traces of vitamin B12. However, the amounts are so small and vary so greatly that these can’t be considered reliable sources of vitamin B12.
The recommended daily amount of vitamin B12 for adults is 4 micrograms. During pregnancy, this increases to 4.5 micrograms and when breastfeeding, to 5.5 micrograms. According to the 2012 Swiss Nutrition Report (Schweizerischer Ernährungsbericht), the average daily allowance is 6 micrograms.
As it moves around the body, vitamin B12 is bound to various transport proteins. This makes sure that very little vitamin B12 is lost. The human body only absorbs the vitamin in the last part of the small intestine. Stomach acids, the digestive enzyme pepsin and pancreatic enzymes break down vitamin B12 from food until intrinsic factor (a glycoprotein) can bind with it. Without this macromolecule, the body is unable to absorb vitamin B12.
The body stores vitamin B12 in the liver. Even if someone isn’t getting enough vitamin B12, it will take time for the deficiency to show its effects. The body can continue using its stored reserves for years. The symptoms aren’t always clear. Signs of a deficiency can include:
Vitamin B12 deficiency can also lead to anaemia and nerve damage.
People who regularly eat meat or fish don’t usually get vitamin B12 deficiency. Vegetarians and vegans are at a higher risk of developing the deficiency. However, a study has shown that vegetarians and vegans are aware of this, so they often take supplements to compensate.
There are many different causes for vitamin B12 deficiency. As well as poor nutrition or a reduced ability to absorb it (absorption disorders), other reasons for not getting enough vitamin B12 can include:
All of these can reduce vitamin B12 uptake in the body or sometimes prevent it almost entirely.
There are three different ways of checking for a vitamin B12 deficiency.
People who eat a vegetarian or vegan diet should get their vitamin B12 levels checked on a regular basis. This is particularly important during pregnancy and while breastfeeding, when the body needs more vitamins.
If the deficiency is due to insufficient vitamin B12 in the diet, oral treatment is an option. Daily vitamin B12 will be prescribed in the form of tablets, capsules or drops. They usually contain a much higher dose than the reference value of 4 micrograms. This is because the body can only absorb and use part of that amount.
If the body cannot absorb vitamin B12, tablets won’t help. It means the body also can’t use the vitamin B12. Vitamin B12 will therefore be given as an intramuscular injection. The frequency of these injections will vary depending on the person.
If you have a vitamin B12 deficiency, the first thing to do is treat it. Yet it’s important to assess the underlying cause of the deficiency, too. It could be a sign of a digestive tract disorder.
Vitamin B12 deficiencies are not always easy to detect. A blood test provides the first clues. People at risk include vegetarians, vegans, older people, pregnant women and people with kidney or bowel diseases. The symptoms can vary widely and can’t always be linked to vitamin B12 deficiency. However, early detection and treatment is important because a deficiency can, in some cases, lead to permanent damage.
Evelyne Dürr (Msc in Human Movement Sciences, ETH; CAS workplace health promotion) joined Helsana in 2014. As a health management specialist, she helps customers engage with prevention and health promotion. Evelyne Dürr gave the editorial team advice and input for this article.