What’s better for your gut: lean beef or chicken? Science weighs in

By Tarun Sai LomteReviewed by Susha Cheriyedath, M.Sc.Jul 29 2025

Curious if red meat or chicken is better for your gut? This new study reveals that lean Pirenaica beef could be less disruptive to your gut microbiome than chicken, challenging common dietary assumptions.

Study: Effect of the Consumption of Lean Red Meat from Beef (Pirenaica Breed) Versus Lean White Meat (Chicken) on the Gut Microbiota: A Randomized Cross-Over Study in Healthy Young Adults. Image Credit: bigacis / Shutterstock

In a recent study published in the journal Molecular Nutrition and Food Research, researchers investigated the effects of beef and chicken intake on the gut microbiota.

The gut microbiota has emerged as a key factor in human health and disease. Likewise, diet can modulate microbiome diversity, composition, and metabolic activity. Notably, meat intake has been criticized from environmental, health, and ethical perspectives.

The intake of processed or unprocessed red meat has been a risk factor for type 2 diabetes and cardiovascular diseases. Moreover, consumption patterns of animal-derived products have undergone substantial evolution in recent years.

In addition to their shape, tenderness, and flavor, consumers are interested in their potential health effects, sustainable production methods, and origin. However, there is limited evidence regarding the impact of meat intake on the human gut microbiota.

About the study

In the present study, researchers evaluated the effects of consuming beef and chicken on the gut microbiota. This randomized, crossover-controlled trial included two intervention phases. Participants were healthy young adults without endocrine, metabolic, chronic, or nutrition-related diseases. Participants were, on average, 20 years old, with the majority falling between 18 and 22 years old. Only 16 individuals who completed stool sample collection at all four time points were included in the final analysis, resulting in exploratory findings. They were randomized to a chicken (lean white meat)-based diet or a Pirenaica breed beef (lean red meat from cattle raised in extensive local husbandry systems)-based diet.

Participants were instructed to consume their assigned diets thrice per week and follow their usual diet. They started with a chicken- or beef-based diet for eight weeks and then switched to the alternative diet for another eight weeks, with a five-week washout period between the two periods. The nutritional value of both diets was similar. A food frequency questionnaire was administered at the start of each intervention.

The diet quality index (DQI) was calculated to assess overall dietary habits beyond assigned products. Stool samples were collected at the start and end of each intervention. Bacterial DNA was extracted from stool samples, and its concentration and purity were measured. The gut microbiota was analyzed by amplifying and sequencing the 16S rRNA V3–V4 regions.

Relative abundances and alpha diversity were calculated. A paired Wilcoxon signed-rank test was used to assess differences in alpha diversity indices and relative abundance between the start and end of each experimental period. Intervention effects were examined using a linear mixed‐effects model for repeated measures.

Findings

The study included 16 individuals, with an average age of 20 years. There were no significant differences in sociodemographic characteristics between participants who started with a chicken-based diet and those who began with a beef-based diet. While the baseline DQI was comparable between groups, a significant decrease in DQI was observed after the chicken-based diet, which may have influenced the subsequent microbiota shifts.

After eight weeks, the group eating lean beef showed some decreases in certain types of gut bacteria, but only the reduction in Chloroflexota was considered statistically significant, meaning this change is unlikely to be due to chance. There were no notable changes in overall gut microbial diversity in this group.

In the group eating chicken, there were significant reductions in both Synergistota and Chloroflexota bacteria, as well as clear decreases in measures of gut microbial richness and diversity. Statistical significance means these changes are unlikely to be due to chance.

Looking more closely at specific bacteria, the beef-based diet led to a significant increase in Blautia and decreases in Eubacterium halli group, Roseburia, and Coprococcus. The chicken-based diet resulted in decreases in several bacteria, including Eubacterium eligens group, Saccharofermentans, Bacteroides, Adlercreutzia, and Lachnospira, and increases in Blautia, Sphingomonas, and Family XIII AD3011 group.

The linear mixed model revealed that both dietary interventions had a significant influence on bacterial phyla. Both diets were significantly associated with reductions in Synergistota and Chloroflexota and an increase in Bacillota. Moreover, both diets significantly decreased species richness, Shannon's index, and Fisher’s index. However, the inverse Simpson index showed a significant reduction only after the introduction of the chicken-based diet.

There was a significant period-related effect: the relative abundance of Synergistota and Chloroflexota increased while that of Bacillota decreased during the second period. In addition, alpha diversity exhibited substantial increases in species richness, Shannon, and Fisher’s indices during the second experimental period relative to the first period.

The chicken-based diet was associated with a broader decrease in microbial functional capacity, including reductions in pathways linked to the initiation of fatty acid biosynthesis, gluconeogenesis, and the biosynthesis of aromatic amino acids. Microbial functional activity was relatively stable after the beef-based diet intervention.

Conclusions

In sum, the findings indicate modest changes in microbial composition at the phylum level following chicken- or beef-based diets, with no significant differences between the two interventions. While both diets decreased microbial richness and diversity, significant reductions were only observed after the chicken-based diet, suggesting that the beef-based diet might have a relatively milder impact on microbial diversity.

The authors note that results should be interpreted with caution due to the small sample size and the exploratory nature of the study. Additionally, the specific local and extensive production system of the Pirenaica beef may limit generalizability to other red meats.