Wolffia globosa–Mankai Plant-Based Protein Contains Bioactive Vitamin B(12) and Is Well Absorbed in Humans

Background: Rare plants that contain corrinoid compounds mostly comprise cobalamin analogues, which may compete with cobalamin (vitamin B(12) (B(12))) metabolism. We examined the presence of B(12) in a cultivated strain of an aquatic plant: Wolffia globosa (Mankai), and predicted functional pathways using gut-bioreactor, and the effects of long-term Mankai consumption as a partial meat substitute, on serum B(12) concentrations. Methods: We used microbiological assay, liquid-chromatography/electrospray-ionization-tandem-mass-spectrometry (LC-MS/MS), and anoxic bioreactors for the B(12) experiments. We explored the effect of a green Mediterranean/low-meat diet, containing 100 g of frozen Mankai shake/day, on serum B(12) levels during the 18-month DIRECT-PLUS (ID:NCT03020186) weight-loss trial, compared with control and Mediterranean diet groups. Results: The B(12) content of Mankai was consistent at different seasons (p = 0.76). Several cobalamin congeners (Hydroxocobalamin(OH-B(12)); 5-deoxyadenosylcobalamin(Ado-B(12)); methylcobalamin(Me-B(12)); cyanocobalamin(CN-B(12))) were identified in Mankai extracts, whereas no pseudo B(12) was detected. A higher abundance of 16S-rRNA gene amplicon sequences associated with a genome containing a KEGG ortholog involved in microbial B(12) metabolism were observed, compared with control bioreactors that lacked Mankai. Following the DIRECT-PLUS intervention (n = 294 participants; retention-rate = 89%; baseline B(12) = 420.5 ± 187.8 pg/mL), serum B(12) increased by 5.2% in control, 9.9% in Mediterranean, and 15.4% in Mankai-containing green Mediterranean/low-meat diets (p = 0.025 between extreme groups). Conclusions: Mankai plant contains bioactive B(12) compounds and could serve as a B(12) plant-based food source.