Does a varied diet make for a more varied gut?

You might have heard that a diverse diet is the key to a healthy gut. You likely see colorful plates in wellness articles, filled with different plants and seeds. But what does the actual science say about the link between the variety of your meals and the microbes living inside you?

The evidence is mixed and, in many ways, still incomplete. While some large studies show a connection, other research highlights significant gaps in what we truly know.

In a large study of Chinese populations, researchers found that people with a higher habitual dietary diversity score had greater alpha diversity (the variety of microbes in a single sample) in their gut microbiome ¹. This association was seen in both a discovery cohort of 1,916 people and an independent validation group of 1,320 people ¹. This study also found that higher dietary diversity was linked to a distinct microbial community structure and many microbial species and metabolites ¹.

However, the relationship is not as simple as it seems. One study involving 1,643 participants found that while a composite lifestyle score was linked to gut microbial gene richness (the number of different bacterial genes found in a stool sample), this richness only explained about 27.8% of the effect on insulin resistance (how effectively your body handles sugar) ². This score included diet quality, diet diversity, physical activity, and smoking ². Importantly, the researchers found no significant link between the microbiome's role and body mass index (BMI) ². Individual food groups, like nuts or fish, showed only modest correlations with microbial richness ².

The evidence also contains significant tension. A large systematic review of Indigenous populations found that while those on traditional diets tended to have higher microbial diversity, the difference was not statistically significant and showed high variation between studies ³.

Furthermore, dietary diversity is not defined the same way across the scientific literature. Some researchers use a scale based on six food groups ¹, while others use composite lifestyle scores ². This makes it difficult to compare findings directly.

We are still waiting for definitive proof. Most current evidence comes from observational studies, which show associations rather than cause and effect. A new randomized trial is currently underway to see if a four-week period of consuming a beverage made from 30 different plant species can actually increase microbial diversity in adults with PTSD ⁴. Until these results are in, we cannot say for sure how much plant variety matters for your gut.

The link between what you eat and the diversity of your gut microbes is a promising topic, but the science is still being written. While large cohorts suggest a positive association, the strength of that link and its impact on your overall health remains unclear. As you look at your next meal, remember that the colorful plates of plants and seeds you see are just one part of a much larger, still-unfolding story.