Vitamin B12: The Vegan Blindspot (And Why Older Adults Need It Too)

Vitamin B12 is essential for nerve function and red blood cell formation. Unlike most nutrients, you can't get it from plants. At all.

This creates a genuine problem for vegans — and a less obvious one for older adults, whose bodies absorb less B12 even from animal foods.

Why B12 Deficiency Is So Common

B12 is found almost exclusively in animal products. There's no plant food that naturally contains significant amounts. This is a biochemistry fact, not a lifestyle critique.

But diet isn't the only issue. Between 3% and 43% of older adults are B12 deficient — and the older you are, the higher the risk. Why? Your stomach produces less acid with age, and stomach acid is needed to release B12 from food.

The RDA is only 2.4 mcg — a tiny amount. But if you're not eating animal products, or if your body isn't absorbing well, you're not getting it.

Who's at Risk

• Vegans and strict vegetarians — there is no plant source; supplementation is mandatory
• Adults over 50 — NIH recommends getting most B12 from supplements or fortified foods
• People on metformin — long-term use reduces B12 absorption by 10-30%
• People on PPIs or H2 blockers — acid-reducing medications impair B12 release from food
• People with GI conditions — Crohn's, celiac, and other conditions affect absorption
• People with pernicious anemia — autoimmune condition that destroys the protein needed for absorption

Symptoms of Deficiency

B12 deficiency develops slowly — your body stores years' worth. But when it hits, the symptoms can be serious:

• Fatigue and weakness
• Tingling or numbness in hands and feet (nerve damage)
• Memory problems and confusion
• Mood changes and depression
• Pale or yellowish skin
• Swollen, inflamed tongue

What the Research Says About Supplementation

For People Who Are Deficient: Clear Benefits

This is important because it means you don't necessarily need B12 injections — high-dose oral supplements work.

For Cognitive Decline: It Depends on Status

For Heart Health: Reduced Stroke Risk

B12 lowers homocysteine — an amino acid linked to cardiovascular disease. A Cochrane review found that homocysteine-lowering B vitamins (including B12) reduced stroke risk by 10%.

Source: Martí-Carvajal 2017 (PMID: 28816346)

What Doesn't Work

If You Do Supplement

Cyanocobalamin is the most common and cheapest form. It's synthetic but well-studied and effective.

Methylcobalamin is the active form — no conversion needed. May be preferable for neurological support. Keep away from light (it's less stable).

Dose for deficiency: 1000-2000 mcg daily. The absorption efficiency drops at high doses, but enough gets through.

Drug Interactions

• Metformin — reduces B12 absorption; monitor levels
• PPIs (omeprazole, etc.) — reduce absorption from food; supplements still work
• H2 blockers (famotidine) — similar to PPIs
• High-dose folic acid — can mask B12 deficiency; always ensure B12 is adequate first

The Bottom Line

Vitamin B12 deficiency is:

1. Inevitable for vegans — supplement or eat fortified foods. There is no plant source.
2. Common in older adults — even with adequate meat intake, absorption declines
3. Sneaky — symptoms develop slowly, and nerve damage can become permanent
4. Easy to fix — oral supplements work as well as injections

If you're in a risk group, get your B12 checked. A simple blood test can catch deficiency before it causes problems. And if you're taking high-dose folate for any reason, make sure you're not masking a hidden B12 problem.