The Power of Vitamin B12: A Vital Nutrient for Health and Energy

Vitamin B12 is a water-soluble vitamin that the body needs for various tasks ranging from red blood cell production and DNA synthesis to proper nerve function [1]. A high homocysteine level (15 umol/L) suggests vitamin B12 deficiency [2]. An elevated homocysteine level is associated with an increased risk of cardiovascular disease [3, 4]. There are also positive associations between elevated homocysteine levels and the incidence of both Alzheimer’s disease and dementia [5, 6]. With severe Vitamin B12 deficiency, cyanocobalamin is administered parenterally as a prescription medication, usually by intramuscular injection [2]. Approximately 15% of people aged >60 years in the United States are thought to have undiagnosed cobalamin (vitamin B12 ) deficiency [7].

Cyanocobalamin is the best way to deliver B12.

Cyanocobalamin is a form of vitamin B12 approved by the FDA to treat vitamin deficiencies. Multiple researchers reported the efficacy of cyanocobalamin in treating pernicious anemia, a chronic illness caused by impaired absorption of vitamin B12 [8, 9]. Essentially, all clinical studies used cyanocobalamin, not methylcobalamin, to solve vitamin B12 deficiencies without showing toxic effects [10, 11].

The recommended daily intake of Vitamin B12 is 2-3 micrograms, but supplements can contain up to a couple of thousand micrograms because B12 is poorly absorbed from the gut. Even at the highest doses, the amount of cyanide released is about 20-40 micrograms, which is far less than the amount of naturally occurring cyanide to which one could be exposed by consuming flax seeds, unpasteurized almond milk, fresh apple juice, or apricots.

During the manufacturing of Vitamin B12, fermentation yields adenosylcobalamin and methylcobalamin. However, these compounds tend to degrade when formulated into supplements. Treatment with potassium cyanide converts these into cyanocobalamin, which is very stable. Once ingested, cyanocobalamin is converted back into the original adenosylcobalamin and methylcobalamin. The oral dose of cyanide below which there is no risk has been determined to be 0.5 mg per kg of body weight [12, 13]. This means that an average person weighing 75kg would need to ingest 37.5 milligrams for it to be considered toxic, an enormous amount! Even at a very high dose of vitamin B12 delivered as cyanocobalamin, it would provide about a thousand times less cyanide than is toxic, and the cyanide is excreted in the urine. There is much more cyanide from natural food sources than the cyanide from cyanocobalamin present in Shaklee supplements per serving. If you eat only 1 g of almond (1 whole piece), you can ingest 15.6 times higher cyanide than one serving of cyanocobalamin from Shaklee B complex.

Both methylcobalamin and cyanocobalamin have been found to provide health benefits. After consumption, methylcobalamin and cyanocobalamin supplements are converted to active and usable forms of vitamin B12 in the body. Also, both cyanocobalamin and methylcobalamin are reduced to a cobalamin molecule converted to the active forms of this vitamin within the body’s cells.

No clinical evidence supports the claim that methylcobalamin is better absorbed or more bioavailable than cyanocobalamin. Research suggests that cyanocobalamin might have more benefits [14]. Zugravu and colleagues demonstrated that cyanocobalamin gives better results in maintaining B12, as quantified by the holotranscobalamin, a marker of Vitamin B12 status, compared to methylcobalamin.

Studies showed that both methylcobalamin and a B-complex containing cyanocobalamin were effective in reducing symptoms of diabetic neuropathy, a complication of diabetes that leads to nerve damage [15]. Combining vitamin B12 and pure methylcobalamin benefits somatic symptoms like pain and paresthesia. Overall, there isn’t sufficient evidence to say that one form of B12 is better, and both forms have health benefits and can prevent B12 deficiencies. The most common form of vitamin B12 in dietary supplements is cyanocobalamin [16]. There is no evidence that absorption rates of vitamin B12 in supplements vary by form. Both benefit health and can treat and/or prevent vitamin B12 deficiencies [17].


Author: Maciej Chichlowski PhD, PMP



  1. Allen, L.H., Vitamin B-12. Adv Nutr, 2012. 3(1): p. 54-5.
  2. Green, R., et al., Vitamin B(12) deficiency. Nat Rev Dis Primers, 2017. 3: p. 17040.
  3. Djuric, D., et al., Homocysteine and homocysteine-related compounds: an overview of the roles in the pathology of the cardiovascular and nervous systems. Can J Physiol Pharmacol, 2018. 96(10): p. 991-1003.
  4. Debreceni, B. and L. Debreceni, The role of homocysteine-lowering B-vitamins in the primary prevention of cardiovascular disease. Cardiovasc Ther, 2014. 32(3): p. 130-8.
  5. Ho, R.C., et al., Is high homocysteine level a risk factor for cognitive decline in elderly? A systematic review, meta-analysis, and meta-regression. Am J Geriatr Psychiatry, 2011. 19(7): p. 607-17.
  6. Kim, S., et al., Cognitive impairment is associated with elevated serum homocysteine levels among older adults. Eur J Nutr, 2019. 58(1): p. 399-408.
  7. Lindenbaum, J., et al., Prevalence of cobalamin deficiency in the Framingham elderly population. Am J Clin Nutr, 1994. 60(1): p. 2-11.
  8. Andrès, E., et al., Effects of oral crystalline cyanocobalamin 1000 μg/d in the treatment of pernicious anemia: An open-label, prospective study in Ten Patients. Curr Ther Res Clin Exp, 2005. 66(1): p. 13-22.
  9. Kaltenbach, G., et al., Early normalization of low vitamin B12 levels by oral cobalamin therapy in three older patients with pernicious anemia. J Am Geriatr Soc, 2002. 50(11): p. 1914-5.
  10. Stabler, S.P., Clinical practice. Vitamin B12 deficiency. N Engl J Med, 2013. 368(2): p. 149-60.
  11. Lane, L.A. and C. Rojas-Fernandez, Treatment of Vitamin B12–Deficiency Anemia: Oral versus Parenteral Therapy. Annals of Pharmacotherapy, 2002. 36(7-8): p. 1268-1272.
  12. Schrenk, D., et al., Evaluation of the health risks related to the presence of cyanogenic glycosides in foods other than raw apricot kernels. Efsa j, 2019. 17(4): p. e05662.
  13. Rice, N.C., et al., Behavioral toxicity of sodium cyanide following oral ingestion in rats: Dose-dependent onset, severity, survival, and recovery. Food Chem Toxicol, 2018. 114: p. 145-154.
  14. Zugravu, C.A., et al., Efficacy of supplementation with methylcobalamin and cyancobalamin in maintaining the level of serum holotranscobalamin in a group of plant-based diet (vegan) adults. Exp Ther Med, 2021. 22(3): p. 993.
  15. Sun, Y., M.S. Lai, and C.J. Lu, Effectiveness of vitamin B12 on diabetic neuropathy: systematic review of clinical controlled trials. Acta Neurol Taiwan, 2005. 14(2): p. 48-54.
  16. Paul, C. and D.M. Brady, Comparative Bioavailability and Utilization of Particular Forms of B(12) Supplements With Potential to Mitigate B(12)-related Genetic Polymorphisms. Integr Med (Encinitas), 2017. 16(1): p. 42-49.
  17. Gröber, U., K. Kisters, and J. Schmidt, Neuroenhancement with vitamin B12-underestimated neurological significance. Nutrients, 2013. 5(12): p. 5031-45.