4. Discussion
lower gastrointestinal tract
DISEASES
In a series of n-of-1 trials, we profiled the stabilities and dynamics of gut fungi in response to dietary interventions at both individual and population levels. The HC diet, but not the LC diet, may increase the fungal alpha diversity at the populational level. Both dietary interventions may affect the gut fungal community structure (i.e., beta diversity). We identified four gut fungal genera that were enriched after the HC diet and one genus enriched after the LC diet. We identified one fungal genus depleted after the HC diet and five genera depleted after the LC diet. Our results further suggest that the fungus Advancements in microbial detection methods have improved our knowledge of gut mycobiome. According to current databases, the gut mycobiome can be detected in the lower gastrointestinal tract of around 70% of the population, and at least 267 fungal species have been identified in the intestines [Evidence from recent cohort studies and trials suggests that gut fungal composition can be directly driven by diverse dietary intake and patterns [The aggregated results from sequential n-of-1 trials allow us to distinguish gut mycobiome features responding to a specific intervention at a population level. Given that the washout periods returned the participants to the baseline state unaffected by the preceding treatment, the averaged relative abundance of core diet-related fungi exhibited diverse responses to the HC and LC dietary interventions. The present study identified enrichment of the fungal genus Previous studies have examined gut mycobiome composition and its role in health and diseases in small trials or in cohorts of healthy individuals [Our present study has several strengths. First, the repeated cross-over design enables simultaneous comparisons between and within individuals to examine gut mycobiome variation and stability over time. Second, the nature of this feeding trial could help establish the causal effect of dietary intervention on the gut mycobiome. Third, the identified core fungi offer insights into the mechanisms underlying host-mycobiome interaction. Nevertheless, some limitations and unanswered questions remain. First, the long-term effect of dietary macronutrients on the gut mycobiome is still unclear, which could not be addressed in the present study. Second, the health effect of the identified dietary macronutrient-related gut fungi is still uncertain, and larger studies are needed to confirm their relationship with metabolic health. Moreover, the assessment of the abundance of fungal species in the gut based on fecal samples is not rigorously representative of the gut mycobiome, as we cannot rule out that some of the identified fungi may be transient members originating from the diet. Therefore, caution should be taken when interpreting the link between gut fungi and host health, especially when the identified fungi are less likely inhabiting in the digestive tract.