Individuals who carried 9 or more risk alleles for vitamin B12 deficiency had 8.10% higher HbAC1 concentrations (ng/ml) in the lowest tertile of fibre intake (g) (Mean ± S.D.: 4.90 ± 1.00 g) compared to those with 8 or less risk alleles for vitamin B12 deficiency. Here, ADCY8 is linked to vitamin B12 deficiency.