If you lack vitamin B12, you have an increased risk of heart attack, stroke and dementia. We explain the signs of a vitamin B12 deficiency and how you can compensate for it intelligently – with a daily plan. Because B12 is the only vitamin that is not found in fruit and vegetables.

Vitamin B12 is perhaps the most underrated vitamin. The German Society for Nutrition (DGE), together with the professional societies in Switzerland and Austria, has raised the reference value for vitamin B12 (display) from three to four micrograms per day. “This is an estimated value based on studies in which several parameters were measured in the blood,” explains Silke Restemeyer, qualified ecotrophologist and DGE consultant in an interview with FOCUS online.

According to data from the National Consumption Study (NVS II), most adult men and women consume enough vitamin B12, but risk groups are often undersupplied.

These are people over the age of 65, for example, because the absorption and utilization of vitamin B12 from food no longer works so well for them. They only produce the so-called intrinsic factor in smaller quantities. This is an enzyme that, as a transporter, brings the vitamin to the intestinal cells for absorption. Only a fraction of the vitamin can therefore develop its effect.

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Vitamin B12 is actually a collective term for various cobalamins, such as hydroxy- and adenosylcobalamin in fish and meat, and methylcobalamin in milk. As a coenzyme, vitamin B12 is involved in various metabolic processes in the body. The problem: the body cannot produce it itself and it is essential for life. The main tasks of vitamin B12:

The role of vitamin B12 in lowering homocysteine ​​is particularly interesting. Various studies have shown that an elevated homocysteine ​​level significantly increases the risk of heart attack and stroke. Low homocysteine ​​levels, such as those made possible by vitamin B12, are therefore beneficial.

According to its many functions, the signs of a vitamin B12 deficiency are also very different and range from all symptoms of anemia (pallor, tiredness) to concentration problems, dizziness, muscle weakness and neurological disorders and nerve damage such as neuropathy with sensory disturbances in the legs. This nerve damage can be irreversible if the vitamin deficiency persists for a long period of time.

Above all, it is also being discussed how a vitamin B12 deficiency is related to an increased risk of dementia diseases such as Alzheimer’s. “Studies show that cognitive performance is often reduced in the case of vitamin B12 deficiency, but the data is contradictory when it comes to preventing these changes with vitamin B12 supplementation,” explains nutrition expert Restemeyer.

If you notice any of the symptoms mentioned and/or belong to the risk groups, it is best to have a blood test carried out by a doctor. “It is important to measure at least two biomarkers, for example total vitamin B12 and holo-TC (holo-transcobalamin) in the serum or plasma, as well as a meaningful functional parameter such as methylmalonic acid (MMA) or homocysteine ​​in the serum,” advises Silke Restemeyer. The blood test costs from 16 euros.

If the deficiency is not pronounced, it is usually sufficient to modify your diet a bit and focus on the B vitamin. The following foods are rich in vitamin B12: meat, fish, dairy products, eggs.

The DGE gives an example of a daily plan with which the reference value of four micrograms can be achieved:

Total = 4.2 micrograms of vitamin B12


Total = 5.46 micrograms of vitamin B12

Incidentally, vitamin B12 is quite heat-stable, so it is hardly lost when heating, frying and cooking.

On the other hand, anyone who consciously avoids meat or even eggs and dairy products is at high risk of developing a vitamin B12 deficiency. Many vegans and vegetarians then trust that some plant foods also contain the nerve vitamin, such as fermented vegetables or certain algae. Because all other vitamins, including some B vitamins, are also contained in plant foods.

“However, this is not the case for vitamin B12, it is the only vitamin that is found in significant amounts (almost exclusively) in meat, fish, seafood, eggs and dairy products – but not in plant-based ones,” the nutritionist clarifies.

Sauerkraut (through fermentation with the help of bacteria) and algae do indeed provide vitamin B12, but either in such small quantities that they can hardly be considered as a source – or they are so-called vitamin B12 analogues. These forms do not act like the vitamin, but block the B12 transport in the body and thus even trigger the opposite: the body cannot utilize the little effective vitamin B12 that may be present.

“Vegans should definitely and permanently take a vitamin B12 supplement and have their supply regularly checked by a doctor,” advises the nutritionist. Vegetarians who have an increased need for nutrients, for example during pregnancy and breastfeeding, should also ensure an adequate intake of vitamin B12.

If a vitamin B12 deficiency is detected, it should be compensated for by appropriate dietary supplements. This can be taken orally as tablets and capsules. Tolerability and bioavailability are good. Vitamin B12 and “cyanocobalamin as a crystalline substance, which is often found in dietary supplements, is even better utilized by patients with gastritis than vitamin B12 from food,” reports the expert.

Overdoses with the commercially available vitamin B12 food supplements are hardly possible if handled sensibly. Silke Restemeyer: “In a study with dialysis patients, no undesirable effects were recorded after years of taking 2.5 milligrams after each dialysis (i.e. a multiple of the estimated value of 4 or 5 micrograms).” Nevertheless, important: with long-term intake of vitamin B12 preparations, the vitamin B12 status should be checked from time to time.

However, sometimes this active supplementation is not enough. This can be the case when one or more factors are present, such as:

Then the doctor advises a vitamin B12 cure by injection. The vitamin is given to the muscles at intervals of a few days or a week. Depending on the product, an injection costs around five to ten euros.

So far, vitamin B12 has been a vitamin that has often been underestimated. Studies are only gradually revealing how important and wide-ranging its effect is. A clear, preventive effect of vitamin B12 in combination with B6 and folic acid against strokes has been proven.

The vitamin could also play a role in the topic of cancer. However, there are still few and sometimes contradictory studies. But this is where its ability to stabilize DNA and thus prevent mutations could come into play.

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