Fast Facts About Vitamin B12

By: Annabelle Shaffer, Dietetics senior at University of Illinois Urbana-Champaign

Vitamin B12 is an important nutrient needed by the body for healthy nervous and blood cells (NIH, 2011). Having adequate vitamin B12 also aids in the prevention of megaloblastic anemia (NIH, 2011). The recommended dietary allowance for adults is 2.4 micrograms daily (NIH, 2011). The media has touted vitamin B12 for increasing cognitive function, improving cardiovascular health, and increasing energy.

Are these claims true?

Current literature shows that these claims do not yet have adequate support:

Cognitive function:

How the brain thinks and functions is complicated, so it is not surprising that improving or maintaining cognitive function rests solely on vitamin B12.

A randomized controlled trial concluded that correction of vitamin B12 deficiency does not harm or increase cognitive function (Dangour A, et al., 2015). Some correlations between vitamin B12 and cognitive decline have been identified, but more research on the specific role and effect of vitamin B12 is needed (O’Leary and Samman, 2010). 

Cardiovascular health:

Similar to the brain, your heart health is complex.

Multiple studies have studied the impact of vitamin B12 supplementation on total homocysteine (tHcy), a modifiable risk factor for cardiovascular disease. A study performed in 2005 showed a 7% decrease of tHcy with vitamin B12 supplementation (American Journal of Clinical Nutrition, 2005). Similar studies have not seen the same risk reduction. The prevention of stroke through vitamin B12 supplementation has shown similarly mixed results (O’Leary and Samman, 2010). 

Increasing energy:

The causes of tiredness and fatigue can include nutrient deficiencies, organ declines, and stress, as well as other conditions.

Vitamin B12 deficiencies are accompanied by weakness and fatigue. However, unless you are deficient, a supplementation of vitamin B12 will not increase your energy levels or athletic endurance (Lukaski, 2004; NIH, 2011).

The bottom line is that vitamin B12 is important for several body functions, but it has yet to be proven whether it plays a significant role in the prevention of chronic diseases and the improvement of cognitive function.

Where can vitamin B12 be found? What about vitamin B12 deficiency?

Animal products, specifically organ meats, are naturally rich in vitamin B12. It can be found in dairy, eggs, chicken, and fortified cereals in lower amounts. Those following a plant-based diet and the elderly are at a higher risk for deficiency and may require a supplement or more of a focus on vitamin B12 fortified foods. Although vitamin B12 is not one of the “enrichment” vitamins mandated for flour, there are many foods enriched with the vitamin, such as:

  • Fortified meal supplements
  • Fortified instant breakfast drinks
  • Many enriched ready-to-eat cereals
  • Snack mixes made from those ready-to-eat cereals
  • Some frozen waffles and pancakes
  • Some vegetarian or meatless luncheon slices
  • Some fortified energy drinks

So how can you tell? The list of ingredients may say vitamin B12 or cobalamin, its chemical name.

The symptoms of a deficiency include anemia, fatigue, and neurological disorders (Brown, 2017). Deficiencies are diagnosed through blood testing.



Brown, J. (2017). Nutrition Through the Life Cycle. 6th ed. Boston, MA: Cengage, pp.14-15.

Dangour, A., Allen, E., Clarke, R., Elbourne, D., Fletcher, A., Letley, L., Richards, M., Whyte, K., Uauy, R. and Mills, K. (2015). Effects of vitamin B-12 supplementation on neurologic and cognitive function in older people: a randomized controlled trial1,2. The American Journal of Clinical Nutrition, [online] 102(3), pp.639-647. Available at:

O’Leary, F. and Samman, S. (2010). Vitamin B12 in Health and Disease. Nutrients, [online] 2(3), pp.299-316. Available at:

Lukaski, H. (2004). Vitamin and mineral status: effects on physical performance. Nutrition, [online] 20(7-8), pp.632-644. Available at:

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