In healthy adults in the United States, people who eat a wider variety of foods based on evolutionary relationships between those foods have a greater diversity of microbes in their gut.
See the scientific wording
Dietary diversity, measured as the phylogenetic diversity of food choices, is positively correlated with gut microbial alpha diversity in healthy U.S. adults, with a correlation coefficient of r = 0.171.
Correlational — new studies may shift this
ObservationalOne moderate-quality study links this claim to the outcome, but causation is not established.
What the research says
1 study reviewedSupporting (1)
Cross-Sectional StudyHuman2022
People who eat a wider variety of foods tend to have more types of good bacteria in their gut, and this study found exactly that — the more diverse their diet, the more diverse their gut bacteria were.
Contradicting (0)
No contradicting studies found yet
That doesn't mean it's settled — it just means no study has tested the opposite.
Quality-weighted scoring: we follow the GRADE framework — each study is rated High, Moderate, Low, or Very Low based on study design, methodology rigor, and risk of bias. A single high-quality RCT can outweigh several weaker observational studies.
Scores reflect study quality, not just count.
When people eat a wide variety of plant foods, different types of fiber and starches reach the gut untouched by digestion. Specific bacteria that can break down each type of fiber grow better because they get the food they need. This causes more kinds of bacteria to live in the gut, increasing overall microbial diversity.
Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting study
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In healthy adults in the United States, people who eat a wider variety of foods based on evolutionary relationships between those foods have a greater diversity of microbes in their gut.
Mechanism
1 studyEating many different kinds of plants gives your gut bacteria many different types of food. Each type of bacteria can only eat certain kinds of plant fiber, so more variety in food means more kinds of bacteria can grow. This increases the total number of bacterial species living in the gut.
When people eat a wide variety of plant foods, different types of fiber and starches reach the gut untouched by digestion. Specific bacteria that can break down each type of fiber grow better because they get the food they need. This causes more kinds of bacteria to live in the gut, increasing overall microbial diversity.
Plant-derived polysaccharides, including pectin from fruits and resistant starch from cooked grains, escape digestion in the small intestine and enter the colon intact.
Pectin is hydrolyzed by extracellular enzymes secreted by pectinolytic bacteria such as Lachnospira, while resistant starch is fermented by amylolytic bacteria such as Bifidobacterium.
Metabolic breakdown of these polysaccharides provides energy and carbon sources that enable the proliferation of specialized bacterial taxa.
The presence of multiple distinct plant polysaccharides supports the growth of multiple distinct bacterial lineages, increasing the total number of bacterial species in the gut.
Evidence from Studies
Supporting (1)
Community contributions welcome
People who eat a wider variety of foods tend to have more types of good bacteria in their gut, and this study found exactly that — the more diverse their diet, the more diverse their gut bacteria were.
Contradicting (0)
Community contributions welcome
Score Breakdown
No multi-axis breakdown available yet. The overall Pro / Against score above is the best signal.
- No clinical evidence is available; the score reflects mechanistic plausibility only.
What Would Prove This
Per GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this claim, ordered from strongest to weakest.
Systematic Review and Meta-Analysis of Dietary Phylogenetic Diversity and Gut Microbial Alpha Diversity in Healthy Adult Populations
Systematic review and meta-analysis of cross-sectional and longitudinal studies measuring phylogenetic diversity of diet and gut microbial alpha diversity in healthy adult humans, with standardized methods for both exposures and outcomes.
Prospective Cohort Study of Dietary Phylogenetic Diversity and Changes in Gut Microbial Alpha Diversity Over 12 Months in Healthy U.S. Adults
Prospective cohort of 1,000 healthy U.S. adults aged 25–65, with repeated dietary assessments using phylogenetic diversity metrics and fecal microbiome sequencing at baseline, 6 months, and 12 months.
Cross-Sectional Analysis of Dietary Phylogenetic Diversity and Gut Microbial Alpha Diversity in a Representative Sample of Healthy U.S. Adults
Nationwide cross-sectional survey of 5,000 healthy U.S. adults with detailed dietary records analyzed for phylogenetic diversity and stool samples analyzed for alpha diversity using 16S rRNA sequencing.
In Vitro Fermentation Study Testing the Effect of Phylogenetically Diverse Food Extracts on Gut Microbial Community Diversity
Fermentation experiments using human fecal inocula exposed to defined food extracts representing low, medium, and high phylogenetic diversity, with microbial diversity measured via shotgun metagenomics after 24–72 hours.
Animal Model Study of Phylogenetically Diverse Diets on Gut Microbial Alpha Diversity in Germ-Free Mice Colonized with Human Microbiota
Germ-free C57BL/6 mice colonized with human fecal microbiota fed diets with low, medium, or high phylogenetic diversity for 8 weeks, with fecal microbial alpha diversity measured weekly.