Vitamin B12 and Indian vegetarians: the deficiency nobody notices until it is advanced

Vitamin B12 is made by bacteria, not by plants or animals, and it reaches humans almost entirely through animal foods or fortification. That single fact explains why Indian studies keep finding widespread inadequacy: in several vegetarian cohorts around half of apparently healthy adults show low status, and a meta-analysis across Indian populations put overall inadequacy near 51 per cent.

Why it hides for years

The liver stores B12, sometimes for several years, so a diet low in it produces no symptoms for a long time. When symptoms do arrive they are vague enough to be attributed to almost anything: tiredness, poor concentration, low mood, tingling in the hands and feet, a sore tongue, breathlessness on exertion.

The part that matters is the neurological damage, which can become permanent if deficiency runs long enough. That is the reason to act on suspicion here rather than wait for certainty.

High folic acid intake can correct the blood picture of B12 deficiency while the nerve damage continues. In a country with widespread fortification and routine folic acid supplementation in pregnancy, this is a real risk - which is why B12 should be assessed in its own right rather than inferred from a normal haemoglobin.

Who should pay attention

• Lifelong vegetarians and, more strongly, vegans.
• Anyone over 50 - absorption declines with age, independently of diet.
• People on long-term metformin, which reduces B12 absorption.
• People on long-term acid-suppressing medicines such as proton pump inhibitors.
• Anyone with coeliac disease, inflammatory bowel disease, or a history of gastric or bowel surgery.
• Pregnant and breastfeeding vegetarians - infant stores depend on maternal status.
• Heavy alcohol use.

Tests worth asking about

Sources and supplements

For vegetarians, dairy and eggs contribute but usually not enough on an Indian pattern of intake. Fermented foods, spirulina and mushrooms are not reliable sources, and spirulina in particular contains analogues that can appear on a test without doing the job.

• Cyanocobalamin is the most studied, most stable and cheapest form, and works perfectly well for most people.
• Methylcobalamin is widely sold in India and is an active form; it is not clearly superior for general repletion.
• Oral supplementation works even for many people with absorption problems, because a small fraction is absorbed passively at high doses.
• Injections are used for severe deficiency, neurological involvement or proven malabsorption - a doctor decision.
• Fortified foods - some plant milks, breakfast cereals and nutritional yeasts - help maintain status once corrected.
• B12 is water soluble with a wide safety margin, but that is not a reason to self-prescribe high doses instead of testing.

A reasonable plan

If you have eaten a vegetarian or vegan diet for years and have never had B12 assessed, ask for the test at your next check-up. If it is low, treat it under guidance and retest. If it is adequate, a modest maintenance supplement or reliably fortified foods will keep it that way.

Of all the supplements marketed at Indian consumers, this is one of the few with a strong dietary rationale behind it - and unlike most of the aisle, the case for it rests on a blood test rather than on a promise.