Vitamin B12, also known as cobalamin, is one of the most important vitamins for the normal functioning of the human body. It is involved in the formation of red blood cells, in DNA synthesis, in maintaining a healthy nervous system, and in proper metabolism. Despite its great importance, a deficiency of vitamin B12 is surprisingly common — especially among older adults, vegetarians, vegans, and people with certain chronic illnesses.
The deficiency of vitamin B12 does not occur suddenly. It develops slowly, sometimes over years, which makes it even harder to recognize. The symptoms are often mistaken for stress, overwork, depression or aging — delaying diagnosis and treatment. As a result, the body can suffer significantly, and in some cases the damage becomes irreversible.
The Role of Vitamin B12 in the Body
Vitamin B12 plays a key role in several fundamental processes. It is involved in the creation of the myelin sheath of nerve fibers — the protective layer that allows nerve impulses to be transmitted quickly and accurately. Without sufficient B12, the nervous system begins to function unstably, leading to a variety of neurological complaints.
In addition, the vitamin is crucial for the formation of healthy red blood cells. When B12 is lacking, a specific type of anemia can develop — megaloblastic anemia — in which red blood cells are large but non-functional. This leads to reduced oxygen supply to tissues and persistent fatigue.
Vitamin B12 also participates in the metabolism of homocysteine — an amino acid that, at elevated levels, increases the risk of heart attack, stroke and other cardiovascular diseases. If B12 is insufficient, homocysteine concentration in the blood rises, which in turn places additional strain on the heart and blood vessels.
Causes of Vitamin B12 Deficiency
The most common reason for deficiency is insufficient dietary intake. Vitamin B12 is found almost exclusively in foods of animal origin — meat, fish, eggs, milk and dairy products. People who exclude these foods from their diet are at significantly higher risk of deficiency.
Another important reason is impaired absorption. For B12 to be absorbed in the small intestine, a special protein, known as the “intrinsic factor,” which is produced in the stomach, is required. In conditions such as atrophic gastritis, pernicious anemia, after stomach surgeries, or with long-term use of acid-suppressive medications, this mechanism may be disrupted.
Age also plays a significant role. With advancing years, production of stomach acid decreases — necessary for releasing B12 from food. Thus, many older people develop a so-called “silent deficiency” that remains unrecognized for a long time.
Chronic intestinal diseases (like Crohn’s disease, celiac disease), bacterial overgrowth, parasitic infections, and alcoholism can also interfere with the absorption of the vitamin.
Symptoms of Vitamin B12 Deficiency
One of the most characteristic features of B12 deficiency is the wide variety of symptoms. They can affect nearly all systems in the body and often appear gradually.
The most common and early symptom is persistent fatigue that does not go away even after restful sleep. The person feels drained, without energy, with reduced concentration and work capacity. This is due to anemia and the lower oxygen supply to tissues.
From the nervous system side, people may experience tingling, numbness, or burning sensations in the hands and feet. At first these sensations are light, but over time they can become constant and very unpleasant. Coordination and balance may worsen, resulting in unstable gait. In more severe cases — loss of sensation and muscle weakness.
Many people with B12 deficiency suffer from memory, concentration, and thinking problems. Confusion, forgetfulness, difficulty making decisions. In advanced stages — depression, anxiety, irritability, and sometimes dementia-like symptoms.
The cardiovascular system is also affected. Rapid pulse, shortness of breath with minimal exertion, dizziness and headaches are common complaints. The skin becomes pale, sometimes with a slight yellowish tint.
Digestive symptoms may include loss of appetite, weight loss, nausea, bloating, alternating diarrhea and constipation. The tongue often becomes smooth, red and painful — a condition known as glossitis. The mouth may have burning sensation or ulcers.
If deficiency persists and remains untreated, serious and sometimes irreversible damage to the nervous system may occur. Early detection is therefore very important.
Long-Term Health Consequences of Deficiency
Chronic B12 deficiency can lead to serious systemic consequences. The most serious are related to the nervous system. Prolonged damage to the myelin sheath of nerves can lead to permanent neurological deficits — lasting loss of sensitivity, motor problems, impaired coordination and chronic pain.
Mental changes can also become deep and persistent. Untreated deficiency is associated with higher risk for depressive disorders, cognitive decline and even dementia in older age.
Cardiovascular risks arise as well — elevated homocysteine levels (due to low B12) increase the risk of atherosclerosis, heart attacks and strokes. Thus deficiency of a single vitamin indirectly affects some of the most common causes of death in modern society.
In pregnant women, B12 deficiency may lead to serious complications — anemia, premature birth, delayed fetal development, and increased risk for birth defects of the nervous system.
Who is at Highest Risk
Particularly vulnerable are people who don’t consume animal products. Vegans should definitely take vitamin B12 in supplement form because plant foods practically do not contain this vitamin in biologically active form.
Older adults also belong to the high-risk group, even when they have a varied diet. Reduced stomach acidity and weaker digestive function often lead to deficiency despite normal intake.
People with autoimmune diseases, type 1 diabetes, thyroid disorders, chronic gastrointestinal problems, as well as those who take acid-suppressive medications or metformin long-term, should also monitor their B12 levels.
Foods Rich in Vitamin B12
The best natural sources of vitamin B12 are animal-based foods. Beef and veal liver are among the richest sources, containing extremely high amounts of cobalamin. Red meats such as beef, veal, and lamb also provide significant doses.
Fish is another excellent source. Mackerel, salmon, sardines, tuna, and trout contain large amounts of vitamin B12 and at the same time deliver useful omega-3 fatty acids.
Eggs — especially the yolk — as well as milk, cheese and yogurt, also contribute to daily intake. For people who avoid meat but consume dairy, these are important sources.
On the market there are also plant-based foods enriched with vitamin B12 — some plant milks, cereals, and meat substitutes. This may be a useful option for vegans, but it's important to check the label for actual content.
Supplements and When They Are Necessary
When food is not sufficient or absorption is impaired, taking vitamin B12 as a supplement becomes necessary. Supplements can come in the form of tablets, drops, sublingual forms or injections. The choice depends on the specific reason for deficiency and its severity.
In mild deficiencies oral intake is often sufficient. In severe conditions, neurological symptoms or proven malabsorption, injections are preferred — they bypass the digestive system and deliver the vitamin directly into the bloodstream.
Self-treatment is not recommended. It’s best to check B12 levels with a blood test and undergo therapy under medical supervision.
Lifestyle to Prevent Deficiency of Vitamin B12
A full and varied diet is the foundation of prevention. Regular consumption of meat, fish, eggs and dairy products (for people without dietary restrictions) generally provides the quantities of vitamin B12 needed.
For people who avoid animal products, supplements are not a luxury but a necessity. Regular lab monitoring is strongly recommended.
Limiting alcohol is also important, as it worsens absorption of vitamins and damages the liver — the main “storage” of vitamin B12 in the body.
Good care for the digestive system, timely treatment of gastritis, intestinal infections and autoimmune diseases, and wise use of medications also play an important role in maintaining normal levels.
Physical activity, sufficient sleep and stress management don’t directly affect B12 levels, but support overall metabolism and nervous-system health, which indirectly reduces the risk of severe consequences in case of possible deficiency.
Conclusion
Vitamin B12 deficiency is a quiet, underestimated, but extremely serious problem. It can affect both physical and mental health, reduce quality of life, and lead to permanent damage if not caught in time. The good news is that it is completely preventable and treatable, when approached correctly.
Awareness, balanced nutrition, wise use of supplements and regular health check-ups are the key steps toward maintaining optimal vitamin B12 levels. Caring for this small — but extremely important — vitamin is an investment in energy, a clear mind, a healthy heart and a stable nervous system for years to come.