Vitamin B12 – effect, deficiency and overdose
Vitamin B12 (cobalamin) is a water-soluble vitamin that cannot be produced by the body itself, but must be obtained from foods such as herring or liver. Vitamin B12 is particularly important for our nervous system, but also has a protective effect on our cardiovascular system. A lack of vitamin B12 occurs only rarely in Europe, only people who do not eat animal foods have an increased risk. What are the symptoms of a vitamin B12 deficiency, which foods cover the daily requirement and can the vitamin also be overdosed?
Vitamin B12: effect & function
Although our body only needs small amounts of vitamin B12, the vitamin is involved in many important processes in the organism. Among other things, it influences cell growth and cell division and is required for the formation of erythrocytes , i.e. red blood cells.
In addition, vitamin B12 is also of crucial importance for our nervous system, as it is involved in the formation of the myelin sheath that envelops the nerve fibers. Vitamin B12 is also important for our brain. Researchers suspect that people with a vitamin B12 deficiency have a significantly higher risk of developing dementia later on. Likewise, the probability that there will be a reduction in brain mass should increase in these people.
Finally, vitamin B12 is also said to have a protective effect on the cardiovascular system: it converts the amino acid homocysteine, which can have a harmful effect on the heart and circulation, into the harmless amino acid methionine. Through this conversion, vitamin B12 prevents diseases such as arteriosclerosis .
Vitamin B12: daily requirement
According to the recommendation of the German Society for Nutrition (DGE), the daily dose of vitamin B12 for adults is only 4 micrograms and is therefore significantly lower than for other vitamins. The requirement is slightly higher for pregnant and breastfeeding women, at around 4.5 and 5.5 micrograms respectively.
Which foods contain vitamin B12?
Vitamin B12 is mainly found in animal foods such as fish, eggs, meat or dairy products. The daily requirement of vitamin B12 can be covered by eating one of the following foods, for example:
- 7 grams of liver
- 33 grams of herring
- 150 grams of pollock
- 100 grams of boiled beef
- 150 Gramm Camembert
- 3 Owner
- 250 milliliters whole milk
Vitamin B12 deficiency in vegetarians and vegans
A look at the list of foods that are high in vitamin B12 makes it clear that vitamin B12 is only found in significant amounts in foods of animal origin.
For this reason, vegetarians, but especially vegans, must be careful not to suffer from an undersupply of vitamin B12. If there is a risk of a deficiency, you can prevent this by taking vitamin B12 tablets.
In addition to animal foods, very small amounts of vitamin B12 are also contained in plant foods that are bacterially fermented. These foods include sauerkraut, for example. However, whether the body can adequately utilize this form of the vitamin is controversial.
Lack of Vitamin B12
Since vitamin B12 has a very long half-life, meaning the body can store the nutrient for a very long time, a vitamin B12 deficiency develops very slowly. If the supply of vitamin B12 is completely stopped, the body can continue to draw on the reserves in the liver for about two to three years, only then does the deficiency become noticeable. In addition to the liver, vitamin B12 is also stored in the brain, heart and skeletal muscles.
On the one hand, the cause of a vitamin B12 deficiency can be that the body is not getting enough vitamin B12 through food. This can be due to the type of diet, but also to age-related lower food intake or malnutrition due to anorexia (anorexia).
However, it is much more common for the absorption capacity in the gastrointestinal tract to be impaired. Vitamins can normally be absorbed directly into the body via the intestines, but vitamin B12 requires a transport protein – the so-called intrinsic factor.
The production of this intrinsic factor by the stomach cells is often disrupted in older people, since they often suffer from gastric mucosal atrophy, i.e. tissue atrophy in the gastric mucosa. In addition, the production of the factor is also negatively influenced by chronic inflammation of the gastric mucosa, chronic alcohol abuse, drugs such as omeprazole that inhibit the production of gastric acid, and severe inflammation of the intestines such as Crohn’s disease .
Vitamin B12 is also responsible for activating folate in the body. A lack of vitamin B12 can therefore also promote a folate deficiency.
Symptoms of vitamin B12 deficiency
If there is an insufficient supply of vitamin B12 from food or if the amount consumed cannot be utilized, this can lead to a disruption in blood formation and thus to anemia , which is also referred to as anemia in specialist circles. A special form is pernicious anemia, in which the absorption capacity of vitamin B12 in the gastrointestinal tract is disrupted by a lack of intrinsic factor. Anemia is accompanied by symptoms such as paleness, difficulty concentrating and tiredness .
In addition, a vitamin B12 deficiency can also lead to sensory disturbances in the feet and hands. These abnormal sensations are due to disorders in the central nervous system caused by vitamin B12 deficiency. The same applies to memory disorders that can develop up to and including dementia.
Other symptoms that can be caused by a vitamin B12 deficiency are:
- loss of appetite and weight loss
- Gastrointestinal problems such as diarrhea or constipation
- impotence or bladder weakness
- Burning tongue and smooth, red tongue (Hunter glossitis)
- dizziness
- Dysfunctions in the spinal cord (funicular myelosis)
- depressions
- Pain in the legs, feet or pelvis
- visual disturbances
- yellowing of the skin
Vitamin B12: overdose and its side effects
An overdose of vitamin B12 is normally not possible, since vitamin B12 is water-soluble and excess is simply excreted through the kidneys. In some diseases, such as leukemia or liver inflammation, vitamin B12 levels can be too high.
If the micronutrient is used for therapeutic purposes and administered via an injection, an overdose of vitamin B12 is possible, but this usually has no consequences.
Only in rare cases can local allergic reactions and acne-like symptoms occur as a result of the overdose. Other skin changes, such as hives , are also possible.
There have also been reports of an overdose of B vitamins as a result of the increased consumption of foods enriched with micronutrients , such as energy drinks. In these cases, liver inflammation occurred as a side effect. However, vitamin B12 was only one of the overdosed micronutrients here.
The results of a scientific study from the USA also indicate that long-term intake of high-dose vitamin B12 preparations could possibly increase the risk of developing lung cancer in men . As part of this study, 77,118 subjects between the ages of 50 and 76 took vitamin preparations in the form of dietary supplements at least once a week.
Male participants who took at least 55 micrograms of vitamin B12 per day (in addition to their regular diet) during the two-year study had a 30 to 40 percent higher risk of developing lung cancer than those who did not take the supplements. However, further research on this topic is still pending.
The Federal Institute for Risk Assessment (BfR) recommends not to exceed a daily intake of 25 micrograms when taking vitamin B12 in the form of food supplements in order to avoid possible side effects.
Determination of the vitamin B12 value
If a vitamin B12 deficiency is suspected, the vitamin B12 serum level (serum cobalamin level) is usually measured first. The advantage of this test is that it is relatively uncomplicated and therefore inexpensive. Values between 200 and 1,000 ng/l (nanograms per liter) are considered normal here. The disadvantage, however, is that even with slightly low to normal vitamin B12 values in the blood serum, a vitamin B12 deficiency cannot be ruled out, so the significance of this test is limited.
A test to determine the so-called holotranscobalamin (holo-TC) provides more precise results. This is a combination of vitamin B12 and the protein transcobalamin. Vitamin B12 can only be utilized by the body in this combination. A deficiency can be detected particularly early with the help of this test.
This is what the measurement results say in picomoles per liter:
- Holo-TC levels < 35 pmol/L: Vitamin B12 deficiency is likely.
- Holo-TC level 35-50 pmol/l: A vitamin B12 deficiency should be checked more closely.
- Holo-TC level > 50 pmol/l: Vitamin B12 deficiency is unlikely.
Another indicator of a vitamin B12 deficiency is elevated methylmalonic acid levels. Methylmalonic acid (MMA) is a metabolite. The body needs vitamin B12 to be able to use it. If the values are elevated, this indicates a vitamin B12 deficiency. The measurement is carried out using a urine sample or blood serum. Values from 50 to 300 nmol/l (nanomoles per liter) are in the normal range. Kidney disease can also result in elevated MMA levels. If such a disease is suspected, the creatinine values should also be determined, which allow a statement to be made about the kidney function.
Since measuring the MMA value can also identify underlying causes, such as a disruption in the transport of vitamin B12, experts recommend determining both the vitamin B12 serum level and the MMA value.