Vitamin B12 on a plant-based diet: why supplementation matters
Vitamin B12 is needed to make red blood cells, keep nerves healthy and support DNA production. It is made by bacteria, and in practice humans get it almost entirely from animal foods such as meat, fish, eggs and dairy, where it accumulates. Plant foods do not reliably contain active B12, and products often promoted as natural sources, such as spirulina or some seaweeds, mostly contain inactive analogues that do not meet the body's needs. This makes B12 the key nutrient that vegans, and to a lesser extent vegetarians, need to plan for.
The body stores B12 in the liver, so a deficiency can take years to appear after someone stops eating animal products, which can create a false sense of security. Early signs can be vague, including fatigue, low energy, shortness of breath during exercise and pins and needles in the hands or feet. Over time, low B12 can cause anemia and nerve damage that may not be fully reversible, so it is better to prevent it than to wait for symptoms. Older adults and people taking certain medications, such as metformin or acid-reducing drugs, are also at higher risk because absorption falls.
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Calculate my caloriesFor anyone on a fully plant-based diet, the reliable options are a B12 supplement or regularly eating fortified foods such as plant milks, breakfast cereals or nutritional yeast with added B12. Common approaches include a small daily dose or a larger dose a few times per week, since absorption from a single dose is limited. Check product labels, and consider asking a doctor to test your B12 status if you have followed a plant-based diet for a long time, have symptoms or belong to a higher-risk group.
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