Background

Diet strongly affects human metabolic health, partly by modulating gut microbiome. To date, limited research has assessed the effects of different types of red meat on gut microbiota in human adults.

Aims

Our primary aim was to assess the effects of adding unprocessed or processed lean red meats to a healthy U.S.-style lacto-ovo vegetarian eating pattern on gut microbiota in healthy young adults. We also measured cardiometabolic disease risk factors.
Methods: On three occasions, twelve healthy young adults consumed a healthy U.S.-style eating pattern for three weeks. In random order, the three eating patterns were: a healthy U.S.-style lacto-ovo vegetarian diet, the vegetarian diet with 3 ounces/day of cooked unprocessed lean red meat, and the vegetarian diet with 3 ounces/day of cooked processed lean red meat. Stool and fasting blood samples were collected before and during the third week of each dietary intervention. The stool samples were used to measure the types and relative amounts of bacteria (gut microbial composition) at four levels of classification, including overall structure (community) and three levels of taxonomic rank (phylum, family, and genus).

Research findings and discussion

Among healthy young adults, converting a healthy U.S.-style lacto-ovo vegetarian eating pattern to a healthy U.S-style omnivorous eating pattern by adding moderate amounts of unprocessed or processed lean red meats, does not influence the overall gut microbial structure, or improvements in selected blood lipids and lipoproteins in the short term. The effects of adding lean red meats on specific types of gut bacteria were inconsistent and require further research.

Key Findings

  • Adding unprocessed or processed lean red meats to a healthy U.S.-style lacto-ovo vegetarian eating pattern did not influence the community structure of gut microbiota.
  • Adopting a healthy U.S.-style eating pattern stabilized the composition of gut microbiota at the phylum-level, independent of red meat intake.
  • While adding red meat did not lead to different gut microbial composition post-intervention at the phylum level, differences were detected at the family and genus levels. This highlights the importance of evaluating microbial composition at lower taxonomic levels.
  • Adopting a U.S-style healthy eating pattern improved blood lipid profile, which was not affected by the consumption of lean red meat.