Essentials: How to Build, Maintain & Repair Gut Health | Dr. Justin Sonnenburg

Welcome to Huberman Lab Essentials, our series for the most useful science-backed tools for mental and physical performance. I’m Andrew Huberman from Stanford School of Medicine, and I’m joined by Dr. Justin Sonnenburg; to start, what exactly is the microbiome?

People often use microbiome and microbiota interchangeably, and they refer to the vast community of microbes living on and in us, with the greatest density in the colon. It’s a packed, dynamic ecosystem made of hundreds of species—mostly bacteria but also archaea, fungi, eukaryotes, and many viruses—that can account for a large share of the material in our stool.

When do we first get these microbes, and how do they get in?

Most colonization happens at birth, not in the womb, and delivery mode, feeding, pets, and antibiotics all shape the early trajectory. C-section babies often carry communities that resemble skin, while early exposures can steer immune and metabolic development in very different directions.

How do we define a healthy microbiome?

There’s huge individual variation, and work in traditional populations shows very different profiles from people in industrialized nations. It’s possible that what’s common in the West reflects a degraded state influenced by antibiotics and processed diets that raises inflammatory and metabolic risk.

If someone’s gut was off early in life, can they fix it?

Gut communities tend to fall into stable states and often snap back after antibiotics or diet shifts, so lasting change is hard. In mice, multi-generation low-fiber diets erased many species that didn’t return with fiber alone, but diversity came back when missing microbes were reintroduced and then nourished, hinting at future therapeutics plus diet.

What about cleanses or fasting for gut health?

A flush helps only if you follow it with intentional seeding and feeding of beneficial microbes; without a plan, recolonization is left to chance, so be deliberate about diet during the rebuild.

Is avoiding processed foods categorically better for the microbiome?

A plant-rich diet fuels microbes that make short-chain fatty acids like butyrate, which support the gut lining and calm immune activity, while components of processed foods can disrupt mucus, alter microbes, and push metabolism toward disease.

And plant-based, low or non-caloric sweeteners?

We have limited data, but many are extremely sweet so you need little, and their long history of use suggests they may be gentler than some synthetics; good trials are still needed.

Do you avoid artificial sweeteners personally?

I generally avoid them but I’m not rigid, and I don’t worry about the occasional diet soda.

You ran a study comparing high fiber to a high fermented foods diet; what was the idea?

We shifted toward prevention by reshaping immune tone through the microbiome, so we tested a big increase in plant fiber against a diet rich in live fermented foods like unsweetened yogurt, kefir, kimchi, and sauerkraut, with guidance to avoid added sugars and rely on real fermentation, whether store-bought or homemade.

How much fermented food did people eat, and what changed?

Participants averaged more than six servings a day and followed standard serving sizes, and we saw rising gut diversity, stepwise drops in multiple inflammatory markers, damped immune signaling, better bowel habits, and many reports of clearer thinking, steadier energy, and improved sleep.

What stood out in the fiber group?

Benefits depended on starting diversity, so depleted guts often showed limited short-term response; immigrants to the United States frequently lose fiber-degrading microbes, and without reintroduction and exposure, recovery can be difficult.

How do you handle kids, hygiene, and environmental exposure?

We practice context-aware hygiene—wash after public exposures, but a little clean garden dirt is fine—because safe environmental microbes help educate the immune system.

Thoughts on probiotics for general use?

Quality varies widely, so look for independent validation and strains tested for your specific goal, and consider working with a clinician.

And prebiotics?

Purified fibers can favor a few species and lower diversity, while a wide variety of whole plants tends to support a broader community; some people benefit from specific fibers, but rapidly fermentable prebiotics layered on a Western diet may backfire because of fast fermentation, as seen in mice.

Where can people learn more about your work and book?

Erica and I wrote The Good Gut to make the science practical, and you can find our studies through Stanford’s Center for Human Microbiome Studies and our lab website, where we also recruit participants.

Thank you for the insights and the work you do; let’s do it again.