Vitamin B12: what it is, its role in the body, and signs of deficiency

Vit B12 — this is how the name of vitamin B12, or cobalamin, is shortened in messages and in searches. Let's calmly, without panic, go over why it is needed, where it comes from in ordinary food, and by which signs one can suspect that it is lacking.

What vitamin B12 is

It is a group of biologically active substances — cobalamins, whose structure contains a cobalt atom. They are synthesized by bacteria and archaea, and the vitamin is not formed in plants or in the animal body. With food, mainly cyanocobalamin enters the body. The vitamin is water-soluble: leftovers are excreted in urine, and the body stores a reserve in the liver — enough to last several years.

Why the body needs it

B12 is involved in protein metabolism, helps form red blood cells, and supports the nervous system. Red cells carry oxygen with the help of hemoglobin. If the vitamin is lacking, cells become abnormally large and cannot do their job — anemia develops. At the same time, some symptoms appear even without anemia.

Sources of vitamin B12 in the diet

Naturally, it is found only in animal foods: fish, meat, poultry, eggs, milk and dairy products, liver, shellfish. There is no B12 in plant products unless they have been specially fortified. Fortified dry breakfasts and some products with nutritional yeast are an option for those who do not eat animal foods; check the composition on the label.

A reference point for adults from age 14 is 2.4 mcg per day, for pregnant women — 2.6 mcg, for breastfeeding women — 2.8 mcg, and for children — from 0.9 to 1.8 mcg depending on age. The numbers are tiny, and a varied animal-based diet covers them. The best way to meet the requirement is a varied diet of animal products.

Causes and signs of vitamin B12 deficiency

Deficiency occurs when the body does not get the vitamin or cannot absorb it. The most common cause is pernicious anemia: the immune system attacks stomach cells, and B12 from food stops being absorbed. Less often the issue is diet: a vegan diet without supplements and fortified products, very restrictive or long-term poor menus. Some medications can also have an effect, for example anticonvulsants and proton pump inhibitors, as well as surgery on the stomach and intestines and diseases such as celiac disease or Crohn's disease.

Lack is more common in people over 50: among people aged 65–74 — in about 1 in 20, among those aged 75 and older — in 1 in 10.

• severe fatigue and lack of energy;
• tingling, numbness in the hands and feet;
• red, painful tongue, mouth sores;
• muscle weakness, balance problems;
• worsening memory, understanding and judgment, confusion, low mood or anxiety, vision problems.

How deficiency is detected: blood test

Usually symptoms and a blood test result are enough. The earlier this is sorted out, the better: many manifestations go away with treatment, but some nervous system problems may remain forever. Long-term lack also causes complications — from the nervous system, the heart, sometimes temporary infertility and pregnancy complications. Which tests are needed and what your number means is decided by the doctor.

When to see a doctor

A reason to come for an appointment is constant fatigue, tingling in the hands and feet, painful tongue, mouth sores, muscle weakness, worsening memory or vision. Separately — if you are over 50, follow a vegan diet, have had surgery on the stomach or intestines, or live with celiac disease or Crohn's disease: discuss with your doctor whether a test is needed.

A low vitamin B12 value by itself is not a reason to call an ambulance. 103 or 112 — for signs of stroke, heart attack, or another life-threatening condition.

The material is for reference and does not replace a doctor's consultation: it is better to discuss doubts about your test at an appointment.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer