Study Finds Vegans Have Lower Gut Bacterial Diversity Than Meat Eaters

A new study from the University of Copenhagen in Denmark has found that vegans tend to have lower gut bacterial diversity than people who consume meat and other animal products. The findings, published in the scientific journal Microbiome, suggest that lower protein intake may help explain the unexpected difference.

The study involved 150 Danish participants, including 75 vegans and 75 omnivores. Researchers analyzed stool, blood, and urine samples to examine the composition of microorganisms living in the participants’ digestive systems and explore how dietary habits influence gut health.

An Unexpected Discovery About Gut Bacteria

Gut microbial diversity refers to the variety of bacterial species living in the digestive tract. Greater diversity is generally considered an indicator of a healthier, more resilient gut microbiome.

Because fiber-rich diets are believed to support microbial diversity, researchers initially expected vegans, who typically consume more plant-based foods, to have a greater variety of gut bacteria. Instead, they discovered the opposite.

“This came as a big surprise,” said Professor Oluf Borbye Pedersen of the Novo Nordisk Foundation Center for Basic Metabolic Research at the University of Copenhagen. “We expected the vegan group to have greater bacterial diversity than the omnivores, but that was not the case.”

According to Pedersen, high microbial diversity is generally associated with a healthy and resilient gut microbiome.

Could Protein Intake Explain the Difference?

To better understand the findings, researchers examined participants’ dietary habits and identified a notable difference in protein consumption. Among vegans, protein accounted for approximately 12% of total calorie intake, compared with 17% among omnivores. Vegans also consumed more carbohydrates and dietary fiber but less protein and fat.

Interestingly, vegans with the highest protein intake had gut bacterial diversity comparable to that of omnivores, suggesting that protein consumption may play a more significant role in shaping the gut microbiome than previously recognized.

Pedersen noted that protein may be an overlooked factor in understanding gut microbial diversity among people following vegan diets.

Vegans Also Showed Several Health Benefits

Despite having lower overall bacterial diversity, the vegan participants demonstrated several potentially beneficial health indicators. Researchers found higher levels of bacteria involved in breaking down dietary fiber, along with a greater prevalence of a microorganism associated with lower blood pressure. Blood tests also revealed lower blood sugar and cholesterol levels and fewer markers of inflammation.

These findings suggest that lower microbial diversity does not necessarily indicate poorer overall health. The researchers emphasized, however, that the study was relatively small and observational, meaning it identified associations rather than establishing a direct cause-and-effect relationship.

What Does This Mean for a Vegan Diet?

Pedersen cautioned that the findings are insufficient to support specific dietary recommendations. Nevertheless, he emphasized the importance of maintaining a balanced diet that provides adequate nutrients, regardless of whether a person consumes animal products.

Vegans, in particular, should pay attention to their protein intake to ensure they are meeting their nutritional needs. Plant-based protein sources include legumes such as beans and lentils, as well as chia seeds, quinoa, almonds, and other nuts.

While further research is needed to determine how protein intake influences gut microbial diversity, the study highlights an important consideration: the nutritional balance of a diet may matter just as much as whether it is plant-based or includes animal products.