Vitamin B12
Essential for energy production, nerve health and red blood cell formation. Deficiency is extremely common in vegans, vegetarians and anyone over 50 — and the symptoms develop so slowly most people don't notice until the damage is significant.
What is Vitamin B12?
Vitamin B12 (cobalamin) is a water-soluble vitamin that plays critical roles in DNA synthesis, red blood cell formation, neurological function and energy metabolism. Unlike most water-soluble vitamins, B12 is stored in the liver and can last years — which is why deficiency develops slowly but causes serious damage when it arrives.
B12 is found almost exclusively in animal products — meat, fish, eggs and dairy. This makes it the single most important supplement for anyone eating a plant-based diet. But deficiency is also extremely common in people over 50, who produce less stomach acid needed to absorb B12 from food, and in people taking metformin (diabetes medication) or proton pump inhibitors (PPIs), which both block B12 absorption.
What the Research Shows
- Essential for red blood cell production — deficiency causes megaloblastic anaemia
- Critical for myelin sheath maintenance — the protective coating around nerve fibres
- Supports energy metabolism — converts food into usable cellular energy
- Reduces homocysteine levels — high homocysteine is a cardiovascular and cognitive risk factor
- Supports cognitive function and may reduce dementia risk in older adults
- Essential during pregnancy for fetal neural development
- Supports mood regulation through serotonin and dopamine synthesis
Is Vitamin B12 Right for You?
- Are vegan or vegetarian — no reliable plant sources of B12 exist
- Are over 50 — stomach acid production declines with age, reducing absorption
- Take metformin for diabetes — it blocks B12 absorption significantly
- Take PPIs (omeprazole etc.) long term — these reduce stomach acid needed for B12
- Have had gastric bypass or sleeve surgery
- Experience fatigue, brain fog or tingling in hands and feet
B12 deficiency can take years to develop and symptoms (fatigue, cognitive decline, nerve damage) are often attributed to other causes. If you're in a risk group, testing your blood B12 level is worthwhile before symptoms appear.
How to Take Vitamin B12
Sublingual B12 (dissolved under the tongue) bypasses the need for stomach acid and intrinsic factor, making it the best oral delivery method for older adults and anyone with absorption issues. Look for sublingual methylcobalamin tablets.
Methylcobalamin vs Cyanocobalamin
Methylcobalamin — the active, natural form of B12 found in food. Doesn't require conversion in the body. Better retained in tissues. Preferred for neurological support. The best choice for most people.
Adenosylcobalamin — the other active form, used primarily in mitochondrial energy production. Sometimes combined with methylcobalamin in premium products.
Cyanocobalamin — synthetic form, cheapest to produce, found in most budget supplements. Requires conversion to active forms in the body. Effective for most people but contains a small amount of cyanide (harmless at supplement doses) and is less ideal for those with MTHFR gene variants.
Hydroxocobalamin — used in injections, longer lasting in the body than cyanocobalamin. Rarely found in oral supplements.
What Affects B12 Absorption
Metformin — reduces B12 absorption by up to 30%. If you take metformin, B12 supplementation is essentially mandatory and your doctor should monitor your levels.
Proton pump inhibitors (PPIs) — omeprazole, pantoprazole and similar drugs reduce stomach acid, which is needed to release B12 from food. Long-term PPI use commonly causes B12 depletion.
Folate (B9) — a positive interaction. Folate and B12 work together in DNA synthesis and homocysteine metabolism. If you supplement B12, ensure adequate folate intake. Taking them together as a B-complex is a common and sensible approach.
Vitamin C — very high doses of vitamin C (above 500mg) taken at the same time as B12 may reduce absorption. Space them apart if taking both at high doses.