Does Variety In Your Diet Equal Variety In Your Gut Microbiome?

A World Microbiome Day Special

Today is World Microbiome Day, and while I’ll be holding off on the celebratory florals – I certainly won’t be holding anything back when it comes to celebrating our floras.

And a diverse gut flora is certainly something to celebrate!

Defined as the totality of bacteria and other organisms living within the human digestive tract, diversity in our gut flora contributes meaningfully to human health in a multitude of ways – while a lack of diversity, generally referred to as dysbiosis, is considered far from favorable.

While I’m eager to dive deeper into today’s topic, before we do, it’s important to review some foundational aspects of our current understanding of the microbiome's multi-directional relationship with human health and nutrition. 

Let’s get to the good stuff. 

Flora Fundamentals 

Diversity in the gut microbiome is considered a good thing and generally refers to the number of different types of healthy bacteria present in our digestive tract and their relative abundance.

A significant number of common health conditions in North America ( diabetes, PCOS, fatty liver, eczema) are characterized, at least in part, by gut dysbiosis – which I mentioned is primarily characterized by a loss of microbiome diversity.

Microbiome diversity is heavily dependent on lifestyle factors in both directions, like sleep, intermittent fasting, stress, physical activity, smoking as well as drug and medication use.

Nutrition, of course, also has a big role to play. 

My current understanding is that a strategically optimized and varied diet is overwhelmingly likely to contribute to enhanced microbiome diversity because I’ve observed a growing body of scientific evidence suggesting that specific food components have been demonstrated individually to positively influence the gut microbiome.

These components include:

1. Fermented Foods including kombucha, kimchi, kefir, and yogurt … among others. 
2. Prebiotic Fibre including specific types of vegetables, 
3. Dietary Polyphenols including a wide array of foods and beverages such as green tea/coffee
4. Fatty Fish/Omega-3s including salmon, sardines, trout, mackerel, and herring

Now obviously, it isn’t easy to access these dietary components consistently because to do so requires, by default, a diverse and varied dietary pattern carried out by someone who really knows what they are trying to accomplish.  

Dietary Changes Influence The Microbiome  

The good news is that it appears the human gut microbiome responds relatively quickly to changes in one’s diet, which means that it is never too late to make efforts to boost your microbiome.

It is also true, based on very recent work out of the Microbiome journal, that the microbiome of individuals with a baseline higher microbiome diversity will change less in response to dietary changes than those with a lower starting diversity.

This more or less means, as with most things in nutrition, there are diminishing returns on chasing “perfection” for those who already have strong dietary patterns.

This finally brings us to the focal point of today’s article, a paper published late last year in the American Journal Of Clinical Nutrition that appears to be the first piece of literature that I’ve seen an attempt to broadly examine the relationship between whole diet variety and microbiome diversity.

Let’s take a closer look at the findings.

Diet Variety & Microbiome Diversity – the Evidence

In this particular study, the researchers carried out dietary and microbiome analysis in a sample of over one thousand participants.

They generally found that diversity in the participant’s diets was associated with diversity in the participants' microbiome, diversity in the capacity of the microbiome to form different types of beneficial metabolites (known as SCFAs), and better overall health. 

Dietary variety was also associated with reduced insulin resistance and a reduced presence of inflammatory markers, which is not a huge surprise given the role the microbiome plays in both of these areas. 

While a study of his nature certainly has a number of methodological limitations, including how hard it must be to objectively and meaningfully measure “diet diversity,” the findings do support the general notion that I alluded to in the previous section.

That is to say, variety in our diet is a favorable characteristic.

The authors deserve a great deal of credit for being among the first to really explore this topic in a broad and meaningful way, even if more work will need to be done in the area to further our understanding. 

My Thoughts On The Findings

I always tell my clients that our first priority on the nutrition front is to build a strong foundation incorporating key nutrient-dense food groups and that once we are comfortable with that foundation, we should strive for variety in those food groups to the extent to which it's possible.

Even if we take the relatively simple example of fish, which I wrote about recently for Foodguides, it seems clear that omega-3-rich fatty fish like salmon and sardines are far more likely candidates to positively influence the gut microbiome than lean white fish.

For that reason, it is simply insufficient just to pursue “fish intake”; we must pursue variety in fish intake – for those of us who do indeed eat fish.

This sentiment grows even stronger when we consider foods like fruits.

You’ll need to look no further than my recent piece on the role that flavonoid-rich fruit plays in slowing cognitive decline to appreciate just how important variety in fruit intake is to human health and flourishing.

Interestingly enough, the study actually found that variety in fruit intake was a stronger predictor of gut microbiome diversity than variety in vegetable intake.

While it’s hard for me to speculate as to why that might be among the numerous explanations, it is certainly something worth acting on, particularly because fruit, for most people, is more desirable and easier to prepare and incorporate than veggies are.

Concluding Remark

It is safe, if not yet definitive, to say that variety in one’s dietary choices is a predictor of gut microbiome diversity, which in turn is a predictor of overall health.

This, if nothing else, is food for thought.

1. _{Mosca, A., Leclerc, M., & Hugot, J. P. (2016). Gut Microbiota Diversity and Human Diseases: Should We Reintroduce Key Predators in Our Ecosystem?. Frontiers in microbiology, 7, 455.}
2. _{Wastyk, H. C., Fragiadakis, G. K., Perelman, D., Dahan, D., Merrill, B. D., Yu, F. B., Topf, M., Gonzalez, C. G., Van Treuren, W., Han, S., Robinson, J. L., Elias, J. E., Sonnenburg, E. D., Gardner, C. D., & Sonnenburg, J. L. (2021). Gut-microbiota-targeted diets modulate human immune status. Cell, 184(16), 4137–4153.e14.}
3. _{Mohanambal Moorthy, Nathorn Chaiyakunapruk, Sabrina Anne Jacob, & Uma D. Palanisamy. (2020). Prebiotic potential of polyphenols, its effect on gut microbiota and anthropometric/clinical markers: A systematic review of randomised controlled trials. Trends in Food Science & Technology, 99, 634-649. ISSN 0924-2244.}
4. _{Bourdeau-Julien, I., Castonguay-Paradis, S., Rochefort, G., Perron, J., Lamarche, B., Flamand, N., Di Marzo, V., Veilleux, A., & Raymond, F. (2023). The diet rapidly and differentially affects the gut microbiota and host lipid mediators in a healthy population. Microbiome, 11(1), 26.}
5. _{Lee-Sarwar, K. A., & Ramirez, L. (2022). Diversifying your diet portfolio: potential impacts of dietary diversity on the gut microbiome and human health. The American Journal of Clinical Nutrition, 116(4), 844–845.}