Discussion
chronic fatigued IBD, IBD, fatigue
This study aimed to explore the dynamics in plasma levels of B-vitamins and their related vitamers and metabolites in relation to chronic fatigue in patients with quiescent IBD. We found that the plasma level of FMN was lower in patients with chronic fatigue than in patients without fatigue. Furthermore, we found that changes in the plasma levels of riboflavin were significantly different between chronic fatigued IBD patients who had positive effect of oral high doses of thiamine and fatigued patients who did not have effect of high doses of thiamine.The bioactive forms of riboflavin, FMN and flavin adenine dinucleotide (FAD), are essential for the energy production through ATP (Udhayabanu et al. Borren et al. investigated both serum metabolomics and the faecal microbiome in relation to fatigue in patients with quiescent IBD (Borren et al. The mechanisms of B-vitamins in IBD in general and in relation to fatigue is still not fully explored. As thiamine is important for the growth of gut bacteria and studies have shown associations between fatigue and microbiota in healthy controls compared to patients with IBD; further fatigue-studies including B-vitamins and microbiota could add more knowledge to this topic (Borren et al. The TARIF study design was robust and showed significant effect on fatigue of high doses of oral thiamine. However, both the study itself and the post analysis of B-vitamins and related vitamers has some limitations. The study included mostly females. This is no surprise as fatigue is more prevalent in females than in males with IBD (Bager et al. In conclusion, riboflavin and the metabolite FMN were found to be associated with chronic fatigue in patients with quiescent IBD. Levels of other B vitamins, related vitamers, and metabolites were not found to be significantly different between the investigated groups or related to the thiamine intervention.