Vitamin B12 deficiency: Symptoms, consequences and treatment

Our body has a vitamin store, which means that a vitamin B₁₂ deficiency only develops quite slowly.

Vegan diet

Vegans are particularly at risk of developing vitamin B₁₂ deficiency due to their purely plant-based diet, since vitamin B₁₂ is almost exclusively found in products of animal origin.

In highly developed countries, inadequate vitamin B₁₂ intake through food is extremely rare, except for vegans and strict vegetarians who consume few dairy products or eggs. Worldwide, there are an estimated 75 million voluntary vegetarians as well as 1.45 billion people who live as vegetarians due to a lack of options. A strictly vegetarian (vegan) diet provides a maximum of 0.5 μg vitamin B₁₂ per day, which is why this form of diet is one of the main risk factors for vitamin B₁₂ deficiency.

Vegetarians (lacto-, ovo- and rarely also ovo-lacto-vegetarians) often have subclinical deficiencies that manifest as elevated methylmalonic acid or homocysteine levels. The offspring of vegan or strictly vegetarian mothers can also be affected by a B₁₂ deficiency.

The first signs of a vitamin B₁₂ deficiency are often non-specific and subtle. These include fatigue, weakness, lack of drive, concentration disorders as well as dizziness and headaches. Since vitamin B₁₂ is important for blood production, a deficiency can also lead to anaemia. Typical signs of anaemia are pale skin, shortness of breath and tachycardia.

In the long term, an untreated vitamin B₁₂ deficiency can damage the nerves and cause symptoms such as numbness, tingling and muscle weakness due to the ongoing anaemia. Possible consequences include depression, confusion and impaired brain function.

Since the symptoms of vitamin B₁₂ deficiency are often ambiguous, a blood test is indispensable for diagnosis. Here, the standard vitamin B₁₂ value in the blood serum alone is not sufficient, since it is a relatively late and non-specific marker.

Instead, experts recommend determining additional biomarkers such as holotranscobalamin II (Holo-TC) and methylmalonic acid (MMA), which provide a more reliable picture in the combination. Low Holo-TC values below 35 pmol/l indicate an impending deficiency as the earliest marker, while elevated MMA values above 271 nmol/l indicate an already empty vitamin B₁₂ store.

Absorb vitamin B₁₂ via diet

A balanced diet is the best way to prevent vitamin B₁₂ deficiency, but only for people who consume foods of animal origin. This is because the water-soluble vitamin is only found in sufficient quantities in meat, poultry, fish, eggs and dairy products and as a trace element in milk fermented plant-based foods. It can also be obtained from foods fortified with synthetic vitamin B₁₂, such as breakfast cereals and spreads.

Supplement vitamin B₁₂

To prevent a vitamin B₁₂ deficiency, it is recommended that vegans and persons with a very low intake of foods of animal origin take supplements with vitamin B₁₂ or specifically resort to vitamin B₁₂ enriched foods.

According to the German Nutrition Society (DGE), the estimated value for an appropriate supply is 4 micrograms – it is assumed that small amounts of B12 are consumed several times a day in a diet with animal foods, which are absorbed in the body by an active absorption path. In the case of additional, one-time supplementation due to plant-based diets, however, the body uses the passive absorption path for the vitamin, for which higher doses are necessary, because this passive diffusion is less efficient.