Vitamin B12, and why vegetarians run low

Photo by Lior Shapira / Unsplash

Vitamin B12, also called cobalamin, is a water-soluble vitamin the body needs in tiny amounts and cannot make on its own. It is found reliably only in animal foods. That single fact is why a mostly-vegetarian diet, common across much of India, so often runs short of it — quietly, and over years.

What B12 is

Cobalamin is the most chemically complex of the vitamins. It carries an atom of the mineral cobalt at its centre, which is where its name comes from. The body keeps a store of it in the liver, and that store can last a long time — often a few years. This is the catch: a shortfall builds slowly and silently, so the signs can appear long after the diet first fell short (NIH Office of Dietary Supplements).

Its role in the body

B12 does a few jobs that the body cannot manage without:

• Red blood cells. It is needed to make healthy red blood cells. Without enough, the cells come out large and immature — a condition called megaloblastic anaemia.
• DNA. It is required for the synthesis of DNA, the instructions inside every dividing cell.
• The nervous system. It helps maintain myelin, the protective sheath around nerves. This is why a long shortage shows up as nerve trouble, not just tiredness.
• Working with folate. B12 and folate (vitamin B9) depend on each other; a problem with one disturbs the other (MedlinePlus).

Signs of running low

Because the liver’s store drains slowly, deficiency tends to creep in. Common signs include (NIH Office of Dietary Supplements):

• Tiredness, weakness, pale skin and breathlessness — the marks of anaemia.
• Paraesthesia — numbness or a pins-and-needles feeling in the hands and feet.
• Trouble with balance, and changes in memory or mood.
• A sore, smooth tongue and a poor appetite.

One detail matters here. Eating plenty of folate — easy on a vegetable-rich diet — can hide the anaemia of B12 deficiency while nerve damage quietly continues. For that reason B12 is worth checking on its own. Diagnosis is a simple blood test, and it belongs with a doctor, not guesswork.

Why vegetarians run low

B12 is made by bacteria, not by plants or by animals themselves. It then builds up in animal tissues and products. Plant foods are not a dependable source (review of plant B12 sources).

This puts long-term vegetarians, and especially vegans, more at risk of falling short over time. The risk is higher at certain stages — in pregnancy, in breastfed infants of mothers who are themselves low, and in older adults, whose ability to absorb B12 naturally declines.

Some plant foods are often named as B12 sources — nori and other seaweeds, or certain mushrooms. The honest position is that their content is inconsistent and unreliable, and they should not be counted on as your main supply (review of plant B12 sources).

Where B12 reliably comes from

• For lacto-vegetarians, milk and milk products — curd, paneer, cheese — are the most practical everyday source. Eggs add more for those who eat them.
• Fish and meat are rich sources for those who eat them.
• Fortified foods. Some breakfast cereals and fortified plant milks have B12 added. Reading the label is the only way to know.
• Supplements fill the gap where food cannot, and are the usual route for vegans (NIH Office of Dietary Supplements).

Note

B12 is one of the few nutrients where a long-term vegetarian or vegan diet needs a little planning rather than worry.

If you eat little or no animal food, this is the nutrient most worth raising with your doctor. A single blood test shows where you stand. Avoid reaching for high-dose supplements on your own — the right amount depends on your level and your stage of life, and a qualified practitioner can guide it. Planned well, a vegetarian diet handles B12 perfectly; left unwatched, it is the gap that most often opens up.