COVID-19's toll on the elderly and those with diabetes mellitus - Is vitamin B12 deficiency an accomplice?

Med Hypotheses. 2021 Jan;146:110374. doi: 10.1016/j.mehy.2020.110374. Epub 2020 Nov 12.


COVID-19 exacts a disproportionate toll on both the elderly and those with diabetes; these patients are more likely to require costly intensive care, longer hospitalisation, and die from complications. Nations would thus find it extremely difficult to either lift or sustain socially, economically, and politically damaging restrictions that keep this group of people safe. Without a vaccine, there is thus an urgent need to identify potential modifiable risk factors which can help manage overall fatality or recovery rates. Case fatality rates are highly variable between (and even within) nations; nutritional differences have been proposed to account significantly for this disparity. Indeed, vitamin B12 deficiency is a common denominator between the elderly and those with diabetes. The question on hand thus lies on whether managing B12 deficiencies will impact COVID-19 fatality outcome or recovery rates. Herein, we review the latest evidence that shows that B12 deficiency associates in multiple areas very similar to where COVID-19 exerts its damaging effects: immunologically; microbiologically; haematologically; and through endothelial cell signalling-supporting the hypothesis that B12 deficiency is a potential modifiable risk factor in our fight against COVID-19.

Keywords: COVID-19; Diabetes mellitus; Elderly; Folate; Homocysteine; Immune system; One-carbon metabolism; Sars-Cov-2; Vitamin B12.

Publication types

  • Review

MeSH terms

  • Aged
  • COVID-19 / complications*
  • COVID-19 / epidemiology
  • COVID-19 / therapy
  • Comorbidity
  • Critical Care
  • Diabetes Complications / epidemiology*
  • Folic Acid Deficiency / complications
  • Folic Acid Deficiency / epidemiology
  • Gastrointestinal Microbiome
  • Homocysteine / metabolism
  • Humans
  • Models, Biological
  • Obesity / complications
  • Obesity / epidemiology
  • Pandemics
  • Risk Factors
  • SARS-CoV-2 / pathogenicity
  • Severity of Illness Index
  • Vitamin B 12 / therapeutic use
  • Vitamin B 12 Deficiency / complications*
  • Vitamin B 12 Deficiency / epidemiology


  • Homocysteine
  • Vitamin B 12