1. Introduction
While the human gut is home to a complex and diverse community of microbes, including bacteria and fungi, research on the gut microbiome has largely focused on bacteria, with relatively little attention given to the gut mycobiome. This study aims to investigate how diets with different dietary macronutrient distributions impact the gut mycobiome. We investigated gut mycobiome response to high-carbohydrate, low-fat (HC) and low-carbohydrate high-fat (LC) diet interventions based on a series of 72-day feeding-based n-of-1 clinical trials. A total of 30 participants were enrolled and underwent three sets of HC and LC dietary interventions in a randomized sequence. Each set lasted for 24 days with a 6-day washout period between dietary interventions. We collected and analyzed the fungal composition of 317 stool samples before and after each intervention period. To account for intra-individual variation across the three sets, we averaged the mycobiome data from the repeated sets for analysis. Of the 30 participants, 28 (aged 22–34 years) completed the entire intervention. Our results revealed a significant increase in gut fungal alpha diversity (The human gut is inhabited by a diverse and complex community of microbes, such as bacteria, viruses, and fungi, which are critical in maintaining human health. These microorganisms play a vital role in intestinal barrier function, host neurological function, immune system modulation and physiological processes, especially in regulating blood glucose [Like the bacterial microbiome, the gut mycobiome is shaped by various environmental factors, including diet [In the present study, we aimed to explore short-term gut mycobiome variations in response to a high-carbohydrate, low-fat (HC) diet and a low-carbohydrate, high-fat (LC) diet in a cross-over N-of-1 feeding trial among 30 participants over 72 days. The required macronutrient distributions were achieved mainly by modifying the grain consumption, including wheat flour and white rice. As an exploratory analysis, we explored the association of the diet-related gut fungi with dynamics of glycemic traits measured by continuous glucose monitoring during the interventions.