💊 What it does
Vitamin B12 is essential for the formation of red blood cells, the maintenance of the nervous system, and DNA synthesis. It works closely with folate in a biochemical cycle that, when disrupted, causes megaloblastic anaemia and — critically — progressive nerve damage that can become irreversible if deficiency goes undetected for years. B12 is one of the most important supplements for anyone not eating animal products regularly.
👤 Who needs it
Vegans and plant-based eaters — this is non-negotiable. B12 is found almost exclusively in animal products; plant foods contain no reliable B12 whatsoever (despite claims about spirulina, nori or tempeh — these contain inactive B12 analogues that may actually block absorption of true B12). Vegetarians, especially those who eat few eggs or dairy products. Adults over 50, whose ability to absorb B12 from food declines with age due to reduced stomach acid. Anyone taking metformin (reduces B12 absorption) or proton pump inhibitors long-term.
🥦 Food sources first
Meat, fish, eggs, dairy — all reliable sources. For plant-based eaters, fortified foods (plant milks, nutritional yeast, breakfast cereals) are the only food sources. However, fortified food intake is often inconsistent and insufficient — a reliable supplement is strongly recommended over relying on fortification alone.
🗓 When to supplement
Any vegan or plant-based eater should be supplementing B12 — not as a precaution, but as a necessity. Deficiency develops slowly (the liver stores several years' worth) which means symptoms can appear years after switching to a vegan diet, by which time nerve damage may already have occurred. Do not wait for symptoms.
🏷 Best form to look for
Cyanocobalamin is the most stable, most studied, and most cost-effective form. The body converts it to the two active forms (methylcobalamin and adenosylcobalamin). High-dose daily or every-other-day supplementation (1,000 µg) works via passive absorption and does not depend on intrinsic factor — making it effective even in people with absorption issues.
⏰ When to take it
Can be taken at any time of day with or without food. Sublingual tablets or lozenges (dissolved under the tongue) may improve absorption slightly for some people.