B12 Supplements Are Efficient But Caution With Folic Acid

A July 2018 study 1 looked at whether vegans who take vitamin B12 supplements are more likely to be B12 deficient than lacto-ovo vegetarians (those that eat dairy and eggs). I also consider at the end of this blog some troubling issues with folic acid (the synthetic version of vitamin B9).

Study abstract


Cobalamin (one of the names 2 by which vitamin B12 is known) deficiency represents a health issue for vegetarians, especially vegans, if supplements are not consumed. Vitamin B12 serum levels, traditionally used to assess the vitamin B12 status, can be normal under functional deficiency conditions. [Thus. it’s important to find another, more reliable, method of checking whether a person has a B12 deficiency,  something that’s really not what you want to have – see B12 Deficiency below.]

In this regard, methylmalonic acid (MMA 3 ) has proven 4 5 to be a more specific marker to detect subclinical 6 vitamin B12 deficiency.

Study method

In this study, they presented for the first time the cobalamin status of Spanish vegetarians [‘vegetarians’ being used as a generic term for vegetarians and vegans] using both vitamin B12 and MMA markers 7 , and the effects of the plant-based diet and the intake of vitamin B12 supplements.

They recruited 103 healthy adults (52% of whom were vegans) and assessed dietary preferences and the use of supplements by means of questionnaires and serum 8 samples.

Levels of vitamin B12 and MMA were measured and results were obtained.

Study results

No significant differences between lacto-ovo vegetarians and vegans were observed:

  • 10% of the participants were mild vitamin B12 deficient
  • B12 supplementation (75% of the participants) was associated with higher vitamin B12/lower MMA

Study conclusion

  1. Spanish vegetarians have a low risk of vitamin B12 deficiency as long as they use B12 supplementation
  2. MMA determination is useful to detect mild deficiency

Vitamin B12 deficiency

B12 deficiency can lead to a rather unpleasant condition known as pernicious anaemia. The following are some of the symptoms related to this deficiency:

• Fatigue, profound
• Weakness, especially in arms and legs
• Irreversible nerve damage
• Pale skin, lips, tongue and gums
• Bruising
• Smooth and sore tongue
• Nausea, appetite loss, weight loss, flatulence, diarrhoea, constipation
• Nerve problems – numbness and tingling in hands and feet, muscle weakness, walking problems
• Difficulty maintaining balance
• Shortness of breath
• Depression
• Memory loss, confusion and dementia/disorientation
• Blindness

Final comments

How much B12?

We have already looked in detail at B12 supplementation – how much you need and whether a particular organisation’s supplement source is sufficient 9 . Experts’ opinions vary on just how much we should take: from Dr Greger’s 250-1000 mcg daily 10 to Dr Barnard’s 2.4 mcg daily 11 . But, since there appears to be no evidence in the medical literature of dangers associated with taking an overdose of B12 supplements 12 , it appears to be a good idea to err on the side of taking the higher dose recommendations rather than the lower.

And remember, B12 deficiency is not just something that vegans and vegetarians are at risk of experiencing. As we get past around 50 years of age, our body’s ability to use available B12 diminishes.  Also, research shows that everyone, irrespective of how much meat they eat is at risk of B12 deficiency. One such study 13 found that: “nearly two-fifths of the U.S. population may be flirting with marginal vitamin B12 deficiency.

Caution with folic acid

It’s also worth being cautious about taking folic acid supplements, since they have been shown 14  to mask B12 deficiency. Indeed, there are genuine concerns 15 about taking any folic acid supplements. Naturally-occurring vitamin B9 in plants is called folate, and this is simply not the same as the synthetic folic acid found in supplements. Indeed, there’s increasing research data 16 that links folic acid supplementation to an increased risk of cancer!

The Vegan Society Veg-1 supplement contains 200 mcg of folic acid. I am currently re-evaluating whether it would be wiser to ditch this and opt for a B12 supplement that doesn’t also contain folic acid. Watch this space. In the meantime, I will continue with the Veg-1 plus eating foods which are B12-enriched, such as plant milks and nutritional yeast.

And whilst it may be pointed out that it may take years or even decades, in some cases, for serious health problems to develop because of a B12 deficiency…

If in doubt

In fact, even if you’re not in doubt, I suggest that it’s a sensible idea to have a reasonably regular blood test to ensure that all important levels are healthy – including B12. Personally, I aim for a quarterly or biannual finger-prick test or, as an alternative, an annual venous blood test, using the services of a reputable laboratory.  And this would apply to meat-eaters as well as plant-eaters. You can see the sort of blood results available from simple finger-prick tests on a link within the About Me page 17 .


  1. Plant Foods Hum Nutr. 2018 Jul 3. doi: 10.1007/s11130-018-0677-y. [Epub ahead of print]
    Methylmalonic Acid Levels and their Relation with Cobalamin Supplementation in Spanish Vegetarians.
    Gallego-Narbón A, Zapatera B, Álvarez I, Vaquero MP. []
  2. B12 also known as: B-12, B12, B Complex Vitamin, Bedumil, Cobalamin, Cobalamine, Cobamin, Cobamine, Complexe Vitaminique B, Cyanocobalamin, Cyanocobalamine, Cyanocobalaminum, Cycobemin, Hydroxocobalamin, Hydroxocobalamine, Hydroxocobalaminum, Hydroxocobemine, Hydroxocobémine, Idrossocobalamina, Methylcobalamin, Méthylcobalamine, Vitadurin, Vitadurine, Vitamina B12, Vitamine B12 []
  3. Wikipedia: MMA or Methylmalonic acid []
  4. Clin Lab Haematol. 2001 Jun;23(3):161-5. Homocysteine and methylmalonic acid as indicators of folate and vitamin B12 deficiency in pregnancy. McMullin MF1, Young PB, Bailie KE, Savage GA, Lappin TR, White R. []
  5. PLoS One. 2016; 11(1): e0147843. Methylmalonic Acid and Homocysteine as Indicators of Vitamin B-12 Deficiency in Cancer. Pankaj Vashi, Persis Edwin, Brenten Popiel, Carolyn Lammersfeld, and Digant Gupta. []
  6. Definition of ‘subclinical’: relating to or denoting a disease which is not severe enough to present definite or readily observable symptoms. []
  7. Explanation of the inverse relationship between B12 and MMA serum concentrations []
  8. Difference between blood and serum: In blood, the serum is the component that is neither a blood cell nor a clotting factor; it is the blood plasma not including the fibrinogens – the soluble proteins found in blood plasma. []
  9. Vegan Society Veg-1: Does It Contain Enough B12? []
  10. Dr Greger’s B12 recommendations []
  11. Dr Neal Barnard’s B12 recommendations []
  12. Treatment with high dose vitamin B12 been shown to be safe for more than 50 years []
  13. J Bone Miner Res. 2005 Jan;20(1):152-8. Epub 2004 Oct 25. Low plasma vitamin B12 is associated with lower BMD: the Framingham Osteoporosis Study. Tucker KL, Hannan MT, Qiao N, Jacques PF, Selhub J, Cupples LA, Kiel DP. []
  14. Nutr Rev. 2007 Oct;65(10):451-8. If high folic acid aggravates vitamin B12 deficiency what should be done about it? Johnson MA. []
  15. Biochimie. 2016 Jul;126:71-8. Excessive folic acid intake and relation to adverse health outcome. Selhub J, Rosenberg IH. []
  16. BMJ Oncology Research. Cancer risk with folic acid supplements: a systematic review and meta-analysis. Tale Norbye Wien, Eva Pike, Torbjørn Wisløff, Annetine Staff, Sigbjørn Smeland, Marianne Klemp. []
  17. See Testimonials – What My Clients Are Saying []