Consuming a vegan or vegetarian diet results in different profiles of gut microflora, with lower levels of potentially pathogenic bacteria such as E. coli, than eating a meat-based diet, says a new study in the European Journal of Clinical Nutrition 66, 53–60.

Intestinal microbiota represents the largest and most complex microbial community inhabiting the human body, says the study abstract. In fact, the influence of regular diets on the microbiota was widely unknown until researchers from the department of internal medicine VI, University Hospital, Tübingen, Germany, completed this study.

According to the abstract, researchers “examined fecal samples of vegetarians (n = 144), vegans (n = 105) and an equal number of control subjects consuming an ordinary omnivorous diet who were matched for age and gender.” They found that total counts of “bad” gut bacteria were significantly lower in vegan samples than in controls. Subjects on a vegetarian diet ranked between vegans and controls. The total microbial count did not differ between the groups. In addition, subjects on a vegan or vegetarian diet showed significantly lower stool pH than did controls; and stool pH and counts of harmful bugs such as E. coli and Enterobacteriaceae were significantly correlated across all subgroups.

“Maintaining a strict vegan or vegetarian diet results in a significant shift in the microbiota, while total cell numbers remain unaltered,” concluded the authors.