Plant-based Diets

Vitamin B12 Deficiency

The burgeoning growth and popularity of plant-based diets is a positive on many levels for health. However, it is the increasing prevalence of plant-based vegetarian and vegan diets that presents the challenge of vitamin B12 deficiency for those who follow them. While these diets are often followed to improve health, they do require more vigilance on the part of patients and their practitioners to ensure a deficiency of vitamin B12 does not occur.



The B12 and Vegetarian Diet Paradox

As one of the B vitamins, vitamin B12, or cobalamin, is responsible for the health of nerves and blood cells, as well as the creation of DNA.1 It also helps to prevent the megaloblastic anemia that makes people feel tired and weak.1 Finally, cobalamin is found only in meat, eggs, poultry, dairy products, and other animal foods such as liver, which is why vitamin B12 deficiency is commonly found within vegetarian and vegan patients. 

Symptoms of vitamin B12 deficiency

The signs of deficiency may present as subtle and unrecognizable.2


  • Numbness/pins and needles sensation in hands, legs, or feet
  • Staggering/issues with walking and balance
  • Anemia
  • Weakness and fatigue
  • Cognitive difficulties/memory loss
  • Glossitis (swollen, inflamed tongue)
  • Mouth ulcers


While the long-term consequences of deficiency are not fully known, they may have adverse effects on pregnancy outcomes, vascular, cognitive, bone, and eye health.2 Heart palpitations and pale skin may also present as symptoms.3 It has also been shown that neurological damage can occur in the absence of anemia in up to 30% of vitamin B12 deficiency cases.2


Treating the deficiency

With symptoms present and a positive blood test, vitamin B12 deficiency can be addressed in several ways. Fortified grains found in cereal may help at-risk patients to address any vitamin B12 deficiency, however, it should be noted that some fortified products elevate levels of folate while B12 is still low, potentially masking vitamin B12 deficiency as this practice prevents megaloblastic anema.2 Intramuscular injection of vitamin B12 is another option to provide this nutrient, as are oral supplements. The RDA for vitamin B12 supplementation for adults over age 14 is 2.4 mcg.1 This dose may be used as a starting point based on the patient’s age, lifestyle, and dietary habits. It was shown in a 2005 Cochrane Review that high-dose oral replacement of vitamin B12 was as effective as injection.4


By paying special attention to patients who consume vegetarian and vegan diets, you can ensure they do not become deficient in vitamin B12. Consider implementing a supplementation protocol to address any issues should deficiency be determined.




  1. Vitamin B12 fact sheet for consumers. Accessed January 15, 2020.
  2. O’Leary F, Samman S. Vitamin B12 in health and disease. Nutrients. 2010 Mar;2(3):299-316.
  3. Langan RC, Goodbred AJ. Vitamin B12 deficiency: recognition and management. Am Fam Physician. 2017 Sep 15;96(6):384-389.
  4. Wang H, Li L, Qin L, Song Y, Vidal-Alaball J, Liu T. Oral vitamin B versus intramuscular vitamin B for vitamin B deficiency. Cochrane Database of Systematic Reviews 2018, Issue 3. Art. No.: CD004655. DOI: 10.1002/14651858.CD004655.pub3.