Vitamin B12, also known as cobalamine, plays a fundamental role in red blood cell production, nervous system functioning and DNA synthesis. This water-soluble vitamin is mainly found in products of animal origin and its deficiency affects about 6% of the population of developed countries, with rates of up to 20% among people over 60 years of age. We will explore together why this vitamin deserves your attention and how to ensure optimal intakes.
What is vitamin B12 and why is it essential?
Vitamin B12 belongs to the vitamin B group and is distinguished by its unique molecular structure containing cobalt. We need this vitamin for three major functions: it participates in the formation of red blood cells that carry oxygen in our body, it maintains the myelin sheath that protects our nerves, and it intervenes in the conversion of the homocysteine to methionine, an essential amino acid.
The recommended daily needs vary by age: 2.4 micrograms for adults, 2.6 micrograms for pregnant women and 2.8 micrograms for breastfeeding. Our liver can store between 2 and 5 milligrams of B12, which represents a reserve for 3 to 5 years. This particularity explains why symptoms of deficiency often appear late. To better understand the consequences of insufficiency, you can consult this article in greenwheely details the links between deficiencies and physical manifestations.
Food sources rich in vitamin B12
We find B12 almost exclusively in animal products. Offals are the most concentrated source: 100 grams of beef liver bring 65 micrograms, more than 27 times the recommended daily intake. Fatty fish like salmon provide 3 micrograms per 100 grams, while eggs offer 1.1 microgram per unit.
For people on a vegetarian or vegan diet, fortified foods are an alternative: some fortified vegetable drinks contain up to 1 microgram per 250 ml serving, and some nutritional yeasts can bring 2 to 8 micrograms per tablespoon. Dairy products also contribute 0.4 to 1.2 micrograms per 100 grams depending on the type of product.
Recognize and prevent B12 deficiency
The signs of a deficiency are gradually appearing. We first observe unexplained chronic fatigue, followed by neurological disorders such as tingling in the extremities, difficulties in concentration or balance disorders. Megaloblastic anaemia, characterized by the production of abnormally large red blood cells, appears in advanced cases.
Populations at risk
Several groups are at increased risk of disability. People over the age of 50 have their absorption capacity reduced by 10 to 30% due to reduced gastric acidity. Strict vegans who do not supplement themselves develop deficiency in 60 to 90% of cases according to studies. People who have had bariatric surgery or inflammatory intestinal diseases also take this vitamin less well.
Medical diagnosis
We recommend a blood test if you have suspicious symptoms. A serum level of less than 200 picograms per millilitre usually indicates deficiency, while a level of between 200 and 300 suggests insufficiency. The determination of methylmalonic acid and homocysteine refines the diagnosis in ambiguous situations.
The different forms of supplementation
We have several options to correct or prevent a deficiency. Oral supplements exist in the form of cyanocobalamine (the most stable and economical) or methylcobalamine (active form directly usable). Doses vary from 10 to 2000 micrograms as needed, knowing that our body only absorbs about 1.5% of an oral dose of 1000 micrograms.
Intramuscular injections are necessary in case of severe malabsorption. The standard protocol consists of 1000 micrograms per day for one week, then once a week for one month, before switching to a monthly maintenance injection. This pathway guarantees 100% bioavailability.
Sublingual sprays and patches are interesting alternatives with improved absorption compared to conventional tablets. We find that these forms partially circumvent intestinal malabsorption problems.
Optimize daily vitamin B12 status
We advise you to adopt several simple reflexes. Regularly consume various animal products to naturally cover your needs: 100 grams of red meat twice a week, fatty fish twice a week, and eggs several times weekly ensure sufficient intakes for most people.
If you are on a vegetarian or vegan diet, we recommend a systematic supplement of 250 micrograms per day or 2500 micrograms per week. Check your blood levels regularly, ideally once a year.
Know that some medicines interfere with absorption: long-term proton pump inhibitors reduce absorption by 12 to 65%, and metformin used for diabetes reduces B12 levels by 10 to 30% in chronic users. We suggest appropriate medical follow-up if you take these treatments.
Vitamin B12 is an essential nutrient too often neglected. We hope this guide will help you maintain optimal levels to preserve your nerve, blood and metabolic health over the long term.
