With more than two billion people suffering from malnutrition and diets homogenising globally, it is vital to identify and conserve nutrient-rich species that may contribute to improving food security and diversifying diets. Of the approximately 390,000 vascular plant species known to science, thousands have been reported to be edible, yet their nutritional content remains poorly characterised. Here we use phylogenetic information to identify plants with the greatest potential to support strategies alleviating B-vitamin deficiencies. We predict the B-vitamin profiles of >6,400 edible plants lacking nutritional data and identify 1,044 species as promising key sources of B vitamins. Several of these source species should become conservation priorities, as 63 (6%are threatened in the wild and 272 (26%) are absent from seedbanks. Moreover, many of these conservation-priority source species overlap with hotspots of malnutrition, highlighting the need for safeguarding strategies to ensure that edible plant diversity remains a reservoir of nutrition for future generations, particularly in countries needing it most. Although by no means a silver bullet to tackling malnutrition, conserving a diverse portfolio of edible plants, unravelling their nutritional potentials, and promoting their sustainable use are essential strategies to enhance global nutritional resilience.