Disorders of cobalamin metabolism

Vitamin B12 serostatus in Colombian children and adult women: results from a nationally representative survey

OBJECTIVE

Vitamin B12 deficiency is associated with many adverse health outcomes and is highly prevalent worldwide. The present study assesses the prevalence of vitamin B12 deficiency and marginal deficiency in Colombian children and women and examines the sociodemographic correlates of serum vitamin B12 concentrations in these groups.

DESIGN

Cross-sectional, nationally representative survey.

SETTING

Colombia.

SUBJECTS

Children <18 years old (n 7243), pregnant women (n 1781), and non-pregnant women 18-49 years old (n 499).

RESULTS

The overall prevalence of vitamin B12 deficiency (serum vitamin B12<148 pmol/l) and marginal deficiency (serum vitamin B12=148-221 pmol/l) was, respectively, 6.6 % (95 % CI 5.2%, 8.3%) and 22.5% (95% CI 21.1%, 23.9%). Pregnant women had the highest prevalence of deficiency (18.9 %; 95 % CI 16.6 %, 21.5 %) compared with non-pregnant adult women (18.5%; 95% CI 4.4%, 53.1%) and children (2.8 %; 95 % CI 2.3 % %, 3.3 %). In multivariable analyses among children, mean serum vitamin B12 was positively associated with female sex (12 pmol/l higher compared with males; P=0.004), secondary or higher education of the household head (12 pmol/l higher compared with primary or less; P=0.009) and food security (21 pmol/l higher compared with severe food insecurity; P=0.003). In multivariable analyses among pregnant women, mean serum vitamin B12 was positively associated with education of the household head and inversely associated with living in the National territories, Eastern or Pacific regions.

CONCLUSIONS

The prevalence of vitamin B12 deficiency and marginal deficiency in Colombian women and children is substantial. The burden falls largely on adult women, those with lowest education and those living in the poorest, most rural regions of the country.

Cobalamin

Cobalamin (vitamin B12) is an essential nutrient derived exclusively from bacterial sources. It is an essential cofactor for three known enzymatic reactions. Untreated deficiency, caused by either the autoimmune disease pernicious anemia or nutritional lack, results in a macrocytic anemia and/or subacute combined degeneration of the spinal cord and is eventually fatal. Cobalamin in serum is bound to two proteins, transcobalamin and haptocorrin. The former is responsible for the essential delivery of cobalamin to most tissues. Inadequate tissue availability of cobalamin results in increased concentration of methylmalonic acid and homocyst(e)ine due to inhibition of methylmalonyl-CoA mutase and methionine synthase, respectively. Strict vegetarians have long been known to be at risk of cobalamin deficiency, which develops insidiously over many years. It is now clear that a significant number of the elderly and HIV-positive individuals are also at increased risk of deficiency. Any individual with reduced ability to split cobalamin from food-protein may also become deficient even though intrinsic factor is present. Diagnosis of cobalamin deficiency has frequently relied on total serum cobalamin and the Schilling test. Newer approaches such as analysis of methylmalonic acid, homocyst(e)ine, holotranscobalamin, anti-intrinsic factor antibodies, and serum gastrin may provide more cost-effective testing, as well as identify those with a covert deficiency.