Vitamin B12 Deficiency Defined Using Total Cobalamin, Holo‐Transcobalamin II, and an Algorithm of Both Total Cobalamin and Holo‐Transcobalamin II in Vegetarians, Vegans, and Omnivores

Abstract

Vitamin B12 (cobalamin) is a water‐soluble vitamin essential for purine and pyrimidine synthesis, DNA methylation, and the myelination of nerve cells. As vitamin B12 is only found in animal products, vegetarians and vegans are at an inherently higher risk of developing a deficiency than the omnivorous population. The standard measures used to evaluate vitamin B12 nutriture in the clinical setting include total cobalamin, as well as homocysteine and methylmalonic acid (MMA). Each of these markers have flaws, however, as total cobalamin includes biologically inactive cobalamin, homocysteine can be influenced by folate status, and MMA is not present in significant amounts when vitamin B12 nutriture is adequate or excessive. Because of this, holo‐transcobalamin II (TCII), which is the carrier of biologically active vitamin B12, is becoming increasingly popular in research settings to accurately detect cobalamin status. Consequently, there continues to be a discrepancy between the standard analysis methods used in the clinical and research settings. In this study, we sought to compare deficiency prevalence in omnivores, lacto‐ovo vegetarians, and vegans using three different definitions of vitamin B12 deficiency: serum B12 < 148 pmol/L, serum TCII < 35 pmol/L, and serum B12 < 243 pmol/L + TCII < 35 pmol/L. To accomplish this, we analyzed blood samples of 82 subjects between the ages of 19 and 50 years old (27 omnivores, 27 lacto‐ovo vegetarians, and 28 vegans). Chi squared tests revealed significant differences in deficiency detection across the three deficiency definitions (p=0.046). In particular, there was a significant difference in the frequency of deficiency detected using serum B12 (4.9%) and serum TCII (17.1%) (p=0.025) in the total study population. The prevalence of deficiency detected when using serum TCII, rather than serum total cobalamin, appeared to increase more in lacto‐ovo vegetarians (from 7.4% to 25.9%) and vegans (from 3.6% to 17.9%) than in omnivores (from 2.7% to 7.4%), although this difference was not significant. Changing the clinical standard to detect vitamin B12 deficiency may improve deficiency detection, particularly at early onset. In addition, using TCII to detect deficiency cases may improve detection of marginal cases, which can allow practitioners to treat individuals who are deficient before symptoms progress. Future research is needed to examine the feasibility of using TCII in a clinical setting.Support or Funding InformationGraduate and Professional Student Association, Arizona State University