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Providing perspectives on recent research into vitamins and nutritionals


Vitamin B12 Deficiency and its Contribution to Dementia and Stroke

By Julia Bird

In a recent narrative review, Dr Spence brings attention to the contributory role that vitamin B12 deficiency plays in dementia and stroke risk. Older people are much more likely to be affected by vitamin B12 deficiency. For example, while overall less than 3% of the US population has low vitamin B12 levels, incidence of low vitamin B12 concentrations in people aged over 60 is 5% (Bailey et al.). Another group (Clarke) found that while incidence of low vitamin B12 is about 5% in people aged 65 to 74, for people aged 75 and older, the incidence was greater than 10%.

Changes in the digestive tract due to aging generally cause a decrease in the amount of vitamin B12 that is absorbed, and lower food intakes in general mean that intakes of vitamin B12 are also likely to be lower when people age.

Dementia is both a cause and a result of vitamin B12 deficiency. Food intakes tend to decline as dementia progresses, and even in early dementia, patients may lack the initiative to reach out to health care providers that may be able to help diagnose vitamin B12 deficiency. The symptoms of  vitamin B12 deficiency are similar to dementia in its early stages, and include a decline in mental abilities including memory and decision-making ability, irritability and personality changes. In fact, a study of 100 patients with diagnosed dementia in Germany showed that for 10%, the cause was vitamin B12 deficiency (Djukic). A vicious cycle may emerge in which dementia due to vitamin B12 deficiency is not treated, leading to decreases in appetite that exacerbate deficiency.

In addition, vitamin B12 deficiency and the resulting increase in plasma homocysteine levels is a risk factor for stroke. High homocysteine increases plaque on the carotid artery, and the likelihood of stroke is high when homocysteine is elevated. Vitamin B12 supplements are able to reduce plasma homocysteine concentrations by 7%, according to a review from Clarke and Armitage.

There is a difference, however, between low vitamin B12 levels, and functional vitamin B12 deficiency. This is because only a proportion of vitamin B12 is in circulation, therefore low vitamin B12 levels may exist even though vitamin B12 stores are adequate and vitamin B12 needs are being met. The best way to diagnose vitamin B12 is therefore not by measuring vitamin B12 in the blood. Two specific functional markers of vitamin B12 status are available: both elevated methylmalonic acid and low circulating holotranscobalamin (active vitamin B12 according to Nexus) are better markers of functional deficiency. See our previous post on the controversy in measuring vitamin B12 levels.

Dr Spence stresses that vitamin B12 deficiency is common in the elderly, yet it is often not picked up by health care providers. Daily supplementation, or vitamin B12 injections, are simple and safe interventions that resolve deficiency. Vitamin B12 deficiency is a cause of dementia, and contributes to stroke risk, therefore we need greater awareness among practitioners who care for the elderly.

Main citation:

J. David Spence, Metabolic B12 deficiency: a missed opportunity to prevent dementia and stroke, Nutrition Research, Available online 21 October 2015, ISSN 0271-5317,

Supporting citations:

Bailey RL, Carmel R, Green R, Pfeiffer CM, Cogswell ME, Osterloh JD, Sempos CT, Yetley EA. Monitoring of vitamin B-12 nutritional status in the United States by using plasma methylmalonic acid and serum vitamin B-12. Am J Clin Nutr. 2011 Aug;94(2):552-61. doi: 10.3945/ajcn.111.015222. Epub 2011 Jun 15.

Clarke R, Grimley Evans J, Schneede J, Nexo E, Bates C, Fletcher A, Prentice A, Johnston C, Ueland PM, Refsum H, Sherliker P, Birks J, Whitlock G, Breeze E, Scott JM. Vitamin B12 and folate deficiency in later life. Age Ageing. 2004 Jan;33(1):34-41.

Clarke R, Armitage J. Vitamin supplements and cardiovascular risk: review of the randomized trials of homocysteine-lowering vitamin supplements. Semin Thromb Hemost. 2000;26(3):341-8.

Djukic M, Wedekind D, Franz A, Gremke M, Nau R. Frequency of dementia syndromes with a potentially treatable cause in geriatric in-patients: analysis of a 1-year interval. Eur Arch Psychiatry Clin Neurosci. 2015 Aug;265(5):429-38. doi: 10.1007/s00406-015-0583-3. Epub 2015 Feb 26.

Douglas JW, Lawrence JC. Environmental Considerations for Improving Nutritional Status in Older Adults with Dementia: A Narrative Review. J Acad Nutr Diet. 2015 Jul 30. pii: S2212-2672(15)01110-7. doi: 10.1016/j.jand.2015.06.376. [Epub ahead of print]

Nexo E, Hoffmann-Lücke E. Holotranscobalamin, a marker of vitamin B-12 status: analytical aspects and clinical utility. Am J Clin Nutr. 2011 Jul;94(1):359S-365S. doi: 10.3945/ajcn.111.013458. Epub 2011 May 18.

Sadeghian S, Fallahi F, Salarifar M, Davoodi G, Mahmoodian M, Fallah N, Darvish S, Karimi A. Homocysteine, vitamin B12 and folate levels in premature coronary artery disease. BMC Cardiovasc Disord. 2006 Sep 26;6:38.