RESUMEN
AIMS: To determine the prevalence of vitamin B12 deficiency in an urban south Indian population in individuals with different grades of glucose tolerance. METHODS: A total of 1500 individuals [900 normal glucose tolerance (NGT), 300 prediabetes and 300 type 2 diabetes (T2DM)] who were not on vitamin B12 supplementation were randomly selected from the Chennai Urban Rural Epidemiological Study (CURES) follow-up study. Anthropometric, clinical and biochemical investigations, which included vitamin B12, insulin, homocysteine, HbA1c and serum lipids, were measured. Vitamin B12 ≤ 191 pg/ml was defined as absolute vitamin B12 deficiency and vitamin B12 > 191 pg/ml and ≤ 350 pg/ml as borderline deficiency. RESULTS: The mean levels of vitamin B12 significantly decreased with increasing degrees of glucose tolerance (NGT 444 ± 368; prediabetes 409 ± 246; T2DM 389 ± 211 pg/ml, p = 0.021). The prevalence of absolute vitamin B12 deficiency was 14.9% while 37.6% had borderline deficiency. The prevalence of absolute vitamin B12 deficiency was significantly higher among individuals with T2DM (18.7%) followed by prediabetes (15%) and NGT(13.7%) [p for trend = 0.05]. The prevalence of vitamin B12 significantly increased with age (p < 0.05) and in those with abdominal obesity (p < 0.001). Men and vegetarians had twice the risk of vitamin B12 deficiency compared to women and non-vegetarians, respectively. Among individuals with NGT, prediabetes and T2DM, vitamin B12 negatively correlated with homocysteine. CONCLUSION: This study reports that the levels of vitamin B12 decreased with increasing severity of glucose tolerance.