Vitamin B12 Enriched in Spinach and its Effects on Gut Microbiota

Meat and fermented foods are the main source of vitamin B12 (cobalamin) for human beings. Therefore, daily cobalamin intake is a big problem for vegans. In this study, cyanocobalamin (CNCBL) was added to the culture broth for cobalamin enrichment in spinach. After 36 h of cultivation, the accumulated CNCBL in the spinach leaves (wet weight) was as high as 0.48% (concentration), and the leaves still contained 0.94 ± 0.11 μg/g CNCBL after boiling, which could provide consumer daily requirement of CNCBL. Because CNCBL supplementation had adverse effects on gut microbiota, this study focused on the effect of the combination of spinach and CNCBL on gut microbiota as well. After the boiled leaves were passed through an in vitro gastrointestinal tract simulation system, it was found that the spinach protected CNCBL against the low-pH gastric acid. Moreover, compared with the CNCBL supplement group, the relative abundances of Bacteroides and Firmicutes increased, and the relative abundance of Proteobacteria, especially Escherichia spp., reduced. Analysis of short-chain fatty acids (SCFAs) showed that cobalamin-rich spinach was positively correlated with Bacteroides, propionate, and butyrate. The results showed that the method of enriching spinach with CNCBL was effective and had beneficial effects on gut microbiota and SCFAs.