People who consume a regular, healthy diet have more diverse gut flora with more abundant fiber-fermenting species, according to a new, population-based study led by Danxia Yu, Ph.D., an assistant professor and epidemiologist at Vanderbilt University Medical Center.
The study connects decades of diet data with stool samples collected from adults living in Shanghai, China, and provides a crucial baseline for future research.
“To our knowledge, this is the first large-scale, prospective study evaluating the influence of long-term diet quality and food intakes on the gut microbiome among Chinese adults,” wrote the authors.
A Growing Research Niche
The study was published in The American Journal of Clinical Nutrition and adds to a growing body of work investigating the effects of diet on gut flora. Past analyses suggest large proportions of animal products, sugary beverages, and saturated fats limit microbiome diversity. Plant-based diets, on the other hand, enhance gut flora diversity.
Said Yu, “Most of the previous studies in this area involve small sample sizes; large-scale, population-based studies are emerging but remain limited.”
For their study, Yu and colleagues leveraged stool samples and dietary survey data collected prospectively from 1,920 participants in the broader Shanghai Women’s Health Study and Shanghai Men’s Health Study.
The researchers used 16S rRNA sequencing to identify flora species within the stool samples. They analyzed food intake surveys (which were validated monthly) from the preceding 12 months prior to sample collection. Yu used a method she developed previously to assign a “Healthy Diet Score” (HDS) to each participant based on eight weighted food groups: ascending values for fruits, vegetables, dairy products, fish/seafood and nuts/legumes, descending for refined grains, red meat and processed meat. The higher the score, the healthier the diet.
The analyses revealed that participants in the top versus bottom 20 percent of the HDS had an approximately 3 percent increase in flora diversity. “We found a modest, although statistically significant, association for a higher diet quality with a more diverse gut microbiome,” Yu said.
Focus on Specific Species
The analyses also showed abundance of specific flora species associated with HDS. Researchers found higher levels of fiber-fermenting Firmicutes, including Coprococcus, Faecalibacterium and Bifidobacterium in adults with consistent, healthy diets. People with the highest HDS also had rare Tenericutes species in their guts that were not found in people with low HDS. Specific food groups were also associated with altered flora species. Processed meat intake was associated with decreased Roseburia and increased Fusobacteriaceae.
While the health benefits are beyond the scope of the study, Yu noted, “Several fiber-fermenting bacteria have been shown to have anti-inflammatory, anti-diabetic, and anti-hypertensive effects. They also can produce short-chain fatty acids, B vitamins, and neurotransmitters which may, in turn, promote an individual’s health.”
Future studies could investigate to what extent certain commensals may influence disease processes, Yu said, or how dietary changes might affect a person’s flora and underlie symptoms.