What is the Best Diet for Gut Health?

[Hint: It’s Not What We Thought]

In the last decade alone, we’ve learned so much about the gut, the microbiome, and how to eat in ways that support the health of both. That said, the world of gut health science is fast-paced and constantly changing, with new things uncovered almost every day. Inevitably, some of those findings contradict what we’ve previously known to be true, and we often change our beliefs and recommendations to align with the latest research. 

I’ve seen this happen many times throughout my years practicing medicine. And just recently, I read a new piece of evidence — in the form of a clinical study done by researchers at the Stanford School of Medicine — that revealed something surprising about the best diet for gut health!

You can imagine my excitement… I couldn’t wait to share this with you!!

For years we thought that eating a high fiber diet was the best way to increase microbial diversity in the gut. That’s the whole premise behind Fiber Fueled, a new book by my GI colleague, Dr. Will Bulsiewicz. But this study contradicts what we thought we knew, which is why this week, I wanted to dive into the effect nutrition has on gut microbiome health and inflammatory markers in the body— and how we can all make sure we’re eating to optimize our gut for total wellness. Because as you know (as a reader of my blog), the gut is the cornerstone of your health

A surprising shift in the gut-friendly diet paradigm

When it comes to gut health, there are two measurements that are particularly important. The first is gut microbial diversity, which is the diversity (i.e. range of species) of bacteria living in the intestinal ecosystem. This is important because certain bacteria perform specific functions and low diversity is linked to health issues like obesity and IBS. The second measurement is the levels of inflammatory markers in the gut and blood, which when high can mean a leaky gut and chronic inflammation. In the Stanford study, the scientists found that while a high fiber diet may help gut health in the long-term, the most dramatic improvements in microbial diversity and  inflammatory markers is best achieved through a fermented foods diet (at least in the short-term). We’re talking sauerkraut, kimchi, fermented cottage cheese, yogurt, and kefir—the works. 

Now, if you’re up-to-date on my latest gut health recommendations, you’ll know that it’s not a new discovery that fermented foods are gut-friendly. We’ve long known that fermented foods contain valuable probiotics that promote better digestion and overall better gut health. (In fact, last year around this time I did a three-part blog series on this exact topic!) That said, this discovery points to a potentially major change in the paradigm! Let me explain… 

Previously, we thought fermented foods were a complement to a gut-friendly diet—not the foundation for it—and that a high fiber diet was the most important way to create diversity in the gut microbiome (the Holy Grail of gut health!). This Stanford study, though, suggests that it’s the reverse. Fermented foods should actually be the foundation of a gut-friendly diet. Unfortunately for the proponents of high fiber diets, this study presents evidence that challenges anyone (well, we know some of them) pushing fiber as a cure-all for gut health. I once thought so myself.

My thoughts on fiber vs. fermented foods

As “America’s Gut Doctor,” this study caught my eye and left me thinking about the difference between high fiber foods and fermented foods. The researchers compared the influence of two different diets (both healthy): a fiber-rich diet versus a diet high in fermented foods. 

Let me cut to the chase!

The study findings...

Fermented foods improved microbial diversity and reduced inflammatory markers—challenge the beliefs myself and others previously held around the benefits of fiber for the gut microbiome. I’m not saying that fiber isn’t necessary for optimal gut health, because it absolutely is. Fiber provides a prebiotic food source for our gut flora, which ferments the fiber into short-chain fatty acids like butyrate. These fatty acids are critical for the health of the colon, blood sugar regulation, as well as learning and memory among other things.

Not Enough Fiber

Also, it’s worth noting that the average American isn’t getting nearly as much fiber as is recommended for overall good health. The recommended amount of fiber per day for men and women up to 50 years old is 38 grams and 25 grams, respectively. Meanwhile, the average American only eats 10 to 15 grams of fiber total per day—less than half of the suggested intake.

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