Investigating the importance of queuosine (Q) as a novel micronutrient in human ageing and brain health

This thesis explores the human requirement for Q by quantifying its presence in commonly consumed foods, assessing its levels inhuman biological samples, and evaluating the influence of the gut microbiome on its availability. A dual extraction method and an advanced LC-MS/MS analytical technique were developed and validated to accurately detect both free and tRNA-bound Q metabolites across various sample types.

Analysis of a wide range of UK-based dietary items revealed that Q is unevenly distributed, with dairy products, particularly fermented varieties like probiotic yoghurt, emerging as the richest sources. High levels of various Q metabolites were also identified in edible mushrooms and certain animal-derived foods. Data from the NIDAS cohort showed a wide range in daily Q intake among UK adults, influenced by dietary diversity, with a higher intake associated with consumption of multiple Q-rich food sources.