Is B12 just a vegan problem?
Vitamin B12 is the nutrient vegans are always told to supplement — and they should. But B12 deficiency is far more common than most people assume, and it does not discriminate by diet. A systematic review by Pawlak et al. (2013) found that up to 86.5% of vegans, 41% of vegetarians, and a notable proportion of omnivores showed evidence of B12 deficiency. Data from the EPIC-Oxford cohort — one of the largest UK dietary studies — confirmed that 52% of vegans had serum B12 levels classified as deficient.
If you eat meat regularly, you are not automatically protected. Age, medication use, and gut health all affect how much B12 you actually absorb from food.
What does vitamin B12 do?
Vitamin B12 contributes to a surprisingly wide range of bodily functions. The following are EU-authorised health claims for vitamin B12, retained in UK law:
- Normal functioning of the nervous system — B12 is essential for maintaining the myelin sheath that protects nerve fibres
- Normal psychological function — adequate B12 status supports cognitive function and mood regulation
- Normal red blood cell formation — B12 is required for healthy erythropoiesis; deficiency can lead to megaloblastic anaemia
- Normal energy-yielding metabolism — B12 contributes to the metabolic processes that convert food into usable energy
- Reduction of tiredness and fatigue — particularly relevant when intake or absorption is suboptimal
- Normal homocysteine metabolism — B12 helps convert homocysteine to methionine, supporting cardiovascular health markers
- Normal immune system function — B12 contributes to the normal function of the immune system
These are not marketing claims. They are scientifically assessed and legally authorised under EU Regulation 432/2012.
How common is B12 deficiency in the UK?
The National Diet and Nutrition Survey (NDNS) monitors nutrient status across the UK population. While overt clinical B12 deficiency (serum B12 below 148 pmol/L) affects a smaller percentage of the general population, subclinical deficiency — where levels are low enough to impair function but not trigger obvious symptoms — is considerably more widespread.
Groups at elevated risk include:
- Vegans and vegetarians — plant foods contain no reliable B12 unless fortified. Gilsing et al. (2010) found mean serum B12 in British vegans was 122 pmol/L, well below the threshold for adequacy
- Adults over 50 — age-related decline in stomach acid production reduces B12 liberation from food proteins. Andrès et al. (2004) reviewed B12 deficiency prevalence in elderly populations and found it ranged from 5% to over 40% depending on the threshold used
- Proton pump inhibitor (PPI) users — long-term acid suppression directly impairs B12 absorption from food. The MHRA has issued guidance on monitoring B12 in these patients
- Metformin users — metformin reduces B12 absorption in the ileum. Studies show B12 deficiency prevalence of up to 53% in long-term metformin users compared to 31% in non-users
What are methylcobalamin and cyanocobalamin?
When you pick up a B12 supplement, the form listed on the label matters. The two most common supplemental forms are methylcobalamin and cyanocobalamin, and they differ in meaningful ways.
Methylcobalamin
Methylcobalamin is one of the two biologically active coenzyme forms of B12 found naturally in the body. It serves as a cofactor for the enzyme methionine synthase, which converts homocysteine to methionine — a reaction central to the methylation cycle. Because it is already in its active form, methylcobalamin does not require hepatic conversion before use. Research reviewed by Paul & Brady (2017) suggests that methylcobalamin may be retained better in tissues, particularly in the liver and nervous system, compared to cyanocobalamin.
Cyanocobalamin
Cyanocobalamin is a synthetic form of B12 that does not occur naturally in food or the human body. It is the most widely used form in supplements and fortified foods because it is highly stable, inexpensive to manufacture, and has decades of clinical use behind it. After ingestion, cyanocobalamin must be converted in the liver — first the cyanide group is removed, then the molecule is converted to either methylcobalamin or adenosylcobalamin for use in enzymatic reactions. The cyanide released is in trace quantities that are clinically insignificant in healthy individuals, as reviewed by Thakkar & Billa (2015).
How do the two forms compare?
| Feature | Methylcobalamin | Cyanocobalamin |
|---|---|---|
| Biological status | Active coenzyme form | Synthetic, requires conversion |
| Conversion needed | None — used directly | Hepatic conversion required |
| Stability | Less stable; sensitive to light and heat | Highly stable; longer shelf life |
| Tissue retention | Evidence of better retention in liver and nervous tissue | Lower tissue retention in some studies |
| Cost | Higher | Lower |
| Cyanide content | None | Trace amount released (clinically insignificant) |
| Clinical evidence | Growing body of evidence | Decades of established use |
| Suitability for smokers/kidney disease | Preferred — avoids cyanide exposure | Minimal additional cyanide load, but not ideal |
| Neurological activity | Directly active in nervous system | Must be converted to active form first |
Obeid et al. (2015) reviewed the metabolic processing of different cobalamin forms and concluded that all forms are ultimately reduced to a core cobalamin molecule intracellularly, via the chaperone protein MMACHC. This means both forms can produce the same end-result — but the efficiency and completeness of conversion can vary between individuals, particularly those with genetic polymorphisms affecting B12 metabolism.
How are B12 and folate connected?
B12 and folate are metabolically intertwined through the methylation cycle. Methylcobalamin acts as a cofactor for methionine synthase, the same enzyme that converts 5-methyltetrahydrofolate (5-MTHF) back into tetrahydrofolate — the form of folate needed for DNA synthesis.
When B12 is deficient, this reaction stalls. Folate becomes "trapped" in its methylated form and cannot be recycled, leading to a functional folate deficiency even when folate intake is adequate. This is why B12 and folate deficiencies often present with similar symptoms — megaloblastic anaemia in particular.
The interplay also matters in the other direction. High folic acid intake can mask B12 deficiency by correcting the anaemia while neurological damage continues unchecked. This is one reason why assessing both nutrients together is important, and why PARTICULAR's questionnaire evaluates both.
Who should consider which form?
The answer depends on your individual circumstances:
Most people: either form will effectively raise and maintain B12 levels. Both are well-absorbed when taken orally at supplemental doses.
Vegans and vegetarians: both methylcobalamin and cyanocobalamin are suitable. Consistent daily supplementation matters more than the form chosen.
Older adults (50+): methylcobalamin may be preferable. Age-related decline in liver function can reduce the efficiency of converting cyanocobalamin to its active forms. Methylcobalamin bypasses this conversion step entirely.
PPI and metformin users: higher doses may be needed regardless of form, as both medications impair B12 absorption at the gut level. The form is less important than ensuring adequate dosing and monitoring.
Those with MTHFR polymorphisms or methylation concerns: methylcobalamin provides the methyl group directly, which may be advantageous for individuals with reduced methylation capacity. Paul & Brady (2017) discuss this in detail.
Smokers or those with renal impairment: methylcobalamin avoids the trace cyanide exposure from cyanocobalamin, which is more relevant when clearance capacity is compromised.
Why PARTICULAR carries both forms
Rather than declaring one form universally superior, PARTICULAR includes both methylcobalamin and cyanocobalamin in its ingredient library. Your questionnaire responses determine which form is selected for your personalised formula — based on your age, diet, medication use, and other relevant inputs.
This approach reflects the evidence: both forms are effective, but individual factors determine which is optimal for a given person. A 25-year-old vegan with no medications has different needs from a 60-year-old on long-term PPIs and metformin.
How microgranules protect B12
Vitamin B12 is acid-sensitive, and a significant proportion can degrade in the stomach before reaching the absorption site in the terminal ileum. This is particularly relevant for individuals with normal stomach acid production — the very acid that aids digestion can reduce B12 bioavailability from standard tablets and capsules.
PARTICULAR's microgranule technology addresses this:
- Each granule is individually enteric-coated, protecting the B12 through the acidic stomach environment
- Release is targeted to the small intestine, where B12-intrinsic factor complexes are absorbed
- B12 is released independently from other nutrients that may compete for absorption
- The dose delivered matches what your questionnaire responses indicate you need — not a one-size-fits-all megadose
This matters because B12 absorption is saturable — the intrinsic factor-mediated pathway can only absorb approximately 1.5–2 mcg per dose. Higher doses rely on passive diffusion (roughly 1% absorption). Protecting the full dose through to the intestine ensures maximum utilisation of both pathways.
Key takeaways
- B12 deficiency is not limited to vegans — over-50s, PPI users, and metformin users are all at elevated risk
- Vitamin B12 contributes to normal nervous system function, psychological function, red blood cell formation, energy metabolism, and immune function — all EU-authorised claims
- Methylcobalamin is the biologically active form that requires no conversion and may be better retained in tissues
- Cyanocobalamin is synthetic, more stable, cheaper, and has the longest track record of clinical use
- Both forms are effective — individual factors such as age, genetics, and medication use determine which is optimal
- B12 and folate are metabolically linked — assessing both together is important
- Microgranule delivery protects acid-sensitive B12 through the stomach and targets release to the intestine where absorption occurs
- PARTICULAR's questionnaire selects the right form and dose based on your personal inputs
Sources cited in this article:
- Pawlak R, Parrott SJ, Raj S, et al. "How prevalent is vitamin B(12) deficiency among vegetarians?." Nutr Rev. 2013;71(2):110-7.
- Gilsing AM, Crowe FL, Lloyd-Wright Z, et al. "Serum concentrations of vitamin B12 and folate in British male omnivores, vegetarians and vegans: results from a cross-sectional analysis of the EPIC-Oxford cohort study." Eur J Clin Nutr. 2010;64(9):933-9.
- Andrès E, Loukili NH, Noel E, et al. "Vitamin B12 (cobalamin) deficiency in elderly patients." CMAJ. 2004;171(3):251-9.
- Paul C, Brady DM. "Comparative Bioavailability and Utilization of Particular Forms of B." Integr Med (Encinitas). 2017;16(1):42-49.
- Thakkar K, Billa G. "Treatment of vitamin B12 deficiency-methylcobalamine? Cyancobalamine? Hydroxocobalamin?-clearing the confusion." Eur J Clin Nutr. 2015;69(1):1-2.
- Obeid R, Fedosov SN, Nexo E. "Cobalamin coenzyme forms are not likely to be superior to cyano- and hydroxyl-cobalamin in prevention or treatment of cobalamin deficiency." Mol Nutr Food Res. 2015;59(7):1364-72.
- EU Commission Regulation 432/2012 — Authorised health claims made on foods.