To evaluate the prevalence of vitamin B12 deficiency and factors associated with vitamin B12 status in Amazonian children.

Genetic risk score (GRS), socio-economic and nutritional status, and morbidity data were the independent variables used in multiple linear regression models to evaluate factors associated with vitamin B12 status in a population-based cross-sectional study. GRS was created by summing a number of known risk alleles for low serum vitamin B12.

Acrelândia, western Brazilian Amazon.

Children (n 988) aged <10 years.

Overall prevalence of vitamin B12 deficiency (<150 pmol/l) was 4·2 (95 % CI 3·0, 5·6) % and was highest in children aged <24 months: 13·6 (95 % CI % 8·8, 19·7) %. For children <24 months, wealth index (β=0·017, P=0·030) and animal protein intake (β=0·219, P=0·003) were positively associated with vitamin B12 status. GRS (β=−0·114, P<0·001) and serum homocysteine (β=–0·049, P<0·001) were negatively associated. Among children aged ≥24 months, vitamin B12 status was positively associated with wealth index (β=0·012, P<0·001), height-for-age Z-score (β=0·024, P=0·033) and serum vitamin A (β=0·089, P<0·001). Age≥60 months (β=–0·118, P<0·001), GRS (β=–0·048, P<0·001), maternal schooling <5 years (β=–0·083, P<0·001), low intake of animal-derived foods (β=–0·050, P=0·030), serum homocysteine (β=–0·053, P<0·001), serum folate ≥23·6 nmol/l (β=–0·055, P=0·012) and geohelminth infection (β=–0·141, P=0·017) were negatively associated with vitamin B12 status.

GRS, poverty, low intake of animal-derived foods, geohelminth infection, vitamin A and folate status were important factors associated with vitamin B12 status of children in our study.