Vitamin B12 Status in Vegan and Vegetarian Seventh-Day Adventists: A Systematic Review and Meta-Analysis of Serum Levels and Dietary Intake.

Objective: This systematic review and meta-analysis aimed to evaluate the vitamin B12 status and intake of Seventh-day Adventists following a plant-based diet and compare it with omnivore controls to investigate their susceptibility for vitamin B12 deficiency.

Data source: Peer-reviewed articles were identified through a comprehensive search in PubMed, Scopus, and Google Scholar databases from inception up to the year 2024 using specific keywords related to vitamin B12 and Seventh-day Adventists.

Study inclusion and exclusion criteria: Observational studies published in the English language were included if they reported on vitamin B12 status or intake among plant-based Adventists and compared it with omnivore controls who may or may not have been Adventists. Studies that did not present distinguishable results for vegetarian/vegan from omnivore Adventists or only reported on food item intake without specific vitamin B12 data were excluded.

Data extraction: Two independent reviewers extracted data on study characteristics, vitamin B12 intake, and serum levels using a customised data extraction form, resolving discrepancies through consultation with a third reviewer.

Data synthesis: A meta-analysis was conducted using random-effect models due to anticipated heterogeneity, without any subgroup analysis due to the low number of studies. Sensitivity analysis was performed using the 'leave-on-out' method to assess individual study influence on overall effect size and heterogeneity.

Results: Four studies met inclusion criteria, encompassing 1994 participants. Meta-analysis showed no significant differences in serum vitamin B12 levels (MD: -9.85 pmol/L; 95% CI: -45.64 to 25.94 pmol/L; P = 0.54, I² = 50%) or daily intake (MD: 3.31 mcg/d; 95% CI: -4.70 to 11.32 mcg/d; P = 0.42, I² = 90%) between plant-based Adventists and omnivore controls, although there was high heterogeneity between the studies.

Conclusion: Adventists following a vegan or vegetarian diet did not demonstrate increased risk of vitamin B12 deficiency due to the widespread consumption of fortified foods and supplements. The findings underscore the importance of supplementation and the consumption of fortified foods for maintaining adequate B12 status among vegan or vegetarian Adventists but highlight the need for further studies to confirm these observations in diverse geographical areas.