Vitamin B12 and D status in long-term vegetarians: Impact of diet duration and subtypes in Beijing, China

This study aimed to evaluate vitamin B12 and D levels among long-term vegetarians and to assess the influence of their diet duration and diet subtypes on nutritional status in Beijing, China.

A cross-sectional analysis was conducted on 104 vegetarians (84 vegans, 20 lacto-ovo vegetarians). Serum vitamin B12 and D levels were measured, and demographic, dietary, and supplement use data were collected. Statistical analyses included ANOVA, Kruskal-Wallis tests, chi-square tests, and multivariate regressions.

The prevalence of vitamin B12 deficiency (<200 pg/mL) was 38.5%, with higher rates in vegans (44.1%) than lacto-ovo vegetarians (15.0%, p = 0.021). Vitamin D defi-ciency (<20 ng/mL) affected 84.6% of participants, worsening with longer diet duration (p <0.001), yet showed no significant difference between vegan and lacto-ovo subtypes (85.7% vs 80.0%, p = 0.524). Multivariate analysis revealed negative correlations between diet duration (6-10 years and >10 years) and vita-min B12 and D levels (p <0.05). Lacto-ovo vegetarians showed significantly higher vitamin B12 levels than vegans (p = 0.029), and supplement use improved both vitamins' status (p <0.05).

This study reveals a dual challenge among Beijing long-term vegetarians: vitamin B12 deficiency was strongly associated with the degree of exclusion of animal products from the diet (veganism), while vitamin D deficiency was highly prevalent and worsened with longer diet duration. The near-universal vitamin D deficiency observed in this study suggests that, in the Beijing context, the risk may extend beyond dietary choice, potentially reflecting regional environmental factors; however, this requires confirmation through comparative studies with omnivores controls.