Diet and Gut Microbiome and the "Chicken or Egg" Problem

Area of Science:

• Microbiome research
• Gastroenterology
• Human physiology

Background:

• Intestinal and fecal microbiome composition varies significantly among individuals.
• Current models explain only about 15% of the variance in microbiome diversity using known factors.
• Factors like diet, age, BMI, and gastrointestinal functions influence microbiome signatures.

Purpose of the Study:

• To review the impact of individual factors on gut microbiome diversity.
• To highlight the critical role of intestinal transit time in shaping the microbiome.
• To advocate for the assessment of intestinal phenotype in microbiome studies.

Main Methods:

• Literature review of studies investigating factors influencing microbiome diversity.
• Analysis of associations between host parameters and microbiome composition.
• Examination of the relationship between gastrointestinal transit time and gut microbiota.

Main Results:

• Host factors such as BMI, plasma lipids, and blood pressure show stronger associations with microbiome diversity than diet.
• Gastrointestinal functions, particularly intestinal transit time, are critical effectors of microbiome signatures.
• Changes in transit time alter stool characteristics and bacterial load, impacting microbial communities.

Conclusions:

• A comprehensive assessment of an individual's intestinal phenotype is essential for microbiome research.
• Understanding the intestinal phenotype can help resolve the 'chicken or egg' problem in observational microbiome studies.
• Integrating gastrointestinal transit time measurements may provide deeper insights into microbiome variability.