Vitamin B12 rich foods laid out on a grey/white background

Everything you need to know about vitamin B12

Vitamin B12 (aka. cobalamin or 'methylcobalamin')

Humans obtain almost all of their daily vitamin B12 requirement from animal foods, which can leave vegans and vegetarians particularly vulnerable to vitamin B12 deficiency. Adequate B12 intake is vital for red blood cell production and normal neurological function. It is required for synthesising the fatty acids in myelin which is an important component of normal nerve conduction. In conjunction with folate, it is also necessary for DNA synthesis.

Symptoms of vitamin B12 deficiency generally include symptoms relating to anaemia and altered neurological function, including low energy, reduced exercise tolerance, fatigue, shortness of breath, cognitive dysfunction, weakness, and sensory alterations such as paraesthesia (pins and needles or reduced sensation). Symptoms may be absent or subtle and not all symptoms may be experienced.

Interestingly, the bioavailability of vitamin B12 obtained from dietary supplements is about 50% higher than that obtained via food sources. The recommended dietary intake (RDI) for vitamin B12 is surprisingly low, at only 2.4 micrograms per day for adults. However, higher doses might be required for people who are severely deficient or have issues with absorption or low stomach acidity. Some randomised controlled trials have demonstrated that high dose oral B12 might have similar efficacy to intramuscular injection.

IMUNI recommends that all adults adhering to a mostly plant-based diet should consider daily B12 supplementation with an active physiological form of B12 such as methylcobalamin in order to avoid deficiency and optimise health outcomes.


  1. Vitamin B12. Nutrient Reference Values for Australia and New Zealand. National health and medical research council (NHMRC). [cited 24 Nov 2021]. Available from:

  2. Vitamin B12. Fact Sheet for Health Professionals. National Institutes of Health. Office of Dietary Supplements. [cited 24 Nov 2021]. Available from: