Systematic review of factors influencing human digestive microbiota in healthy adults and interactions between them

Abstract

Introduction: Human digestive microbiota is affected by a wide variety of different factors. The objective of this study was to perform a systematic review that gathers and updates the information available about factors that affect human digestive microbiota in healthy adults older than 19 years. It is also reviewed the way to recover data about these factors in every study to know which of these factors are considered and if some type of interaction between them is studied. Methods: We systematically searched MEDLINE, Web of Science, Scielo, PROSPERO, and Cochrane databases for relevant articles on factors that affect human digestive microbiota. Two authors independently reviewed study eligibility and data extraction. Articles were classified based on the studied factor upon one of the following categories: diet, habits, environment, or chemical exposure. Results: 41 of the articles included a questionnaire addressing factors affecting the human microbiota. We collected the data from the questionnaires used in these studies and analyzed the presence of data about diet, habits, environment, and exposition to chemicals. Analysis of the studies indicates that the assessment of risk factors is often partial or focused on a specific aspect (diet, habits, environment, and chemicals). In addition, there are some factors relevant to the human digestive microbiota that are not being assessed (type of fermentation meals, UP foods consumption, vitamin D administration, snacking, intermittent fasting, the number of daily intakes, type of sport practiced, living with pets or working with another type of animals, type of transportation daily used, place of work, home cleaning habits, treatments with radiotherapy, immune suppressants, corticosteroids, and anovulatory). Discussion: Little is known about the impact of the combined interaction of possible risk factors (diet, habits, environment, and chemical exposure). Further studies are encouraged to evaluate more broadly the risk factors that may influence the diversity of the human digestive microbiota and their interactions.