Diet & Nutrition

An Interview with Jeff Leach, Founder of the Human Food Project

An Interview with Jeff Leach, Founder of the Human Food Project

Jeff Leach, internationally recognized microbiome researcher, is the founder of the Human Food Project and the author of Honor Thy Symbionts and Rewild.

His opinions on health and nutrition have appeared in the New York TimesSan Francisco ChronicleSydney Morning Herald and his peer-reviewed research has been published in the British Journal of NutritionEuropean Journal of Clinical NutritionBioScience and MicrofloraJournal of Archaeological Science, Public Health Nutrition and many others.

As part of his efforts at the Human Food Project, Jeff has spent a great deal of time doing research with rural pastoralists and hunter-gatherer groups in East and Southern Africa.

We are pleased to have Jeff join us to share some of his insights on the microbiome.

How did you get interested in studying the microbiome, and how has your background prepared you for this type of research?
I got interested in the human microbiome about 12-15 years ago after my infant daughter was diagnosed as a type I diabetic. At the time, very few people—outside of researchers—were talking about the role of microbes in human health. Following a little research, I quickly found that microbes 'might' have played a role in her journey.

During your extensive travels to Africa, you have studied how the less globalized populations, like the Hadza hunter-gatherers of Tanzania, acquire microbes from their environment. Will you contrast their lifestyle to ours and share with us how that lifestyle has benefited their microbiome?
The Hadza hunter-gatherers we work with live in a part of Africa (East Africa) that presumably gave rise to our genus Homo. This makes their relationship with the microbial world potentially very interesting as the Hadza literally still hunt and forage for the same animals and plants that our ancestors have for millions of years (minus the megafauna of course). Importantly, this means the Hadza are exposed to the same microbes in the environment that help shape our symbiotic relationship with many of the microbes today.

Since the Hadza live outside 24/7—and are exposed to an extraordinary diversity of microbes from soil, water, butchered animals and plants (above and below ground)—we have found that they harbor nearly twice the gut microbes as the average Westerner.

Our Western lifestyle of reduced exposure to the microbial world and its diversity of microbial life—and our overuse of antibiotics—have likely contributed to the reduced diversity we see in Western populations. An increasing body of evidence suggests that this loss of microbial diversity in Western populations keeps us from optimal health.

The research you have done on the microbiome has led you to explore ways you can alter your own gut environment. Will you talk about some of the changes you have made in your diet and lifestyle that you feel have been particularly beneficial?
I've conducted dozens of experiments on myself as part of our research in Africa and the American Gut project I co-founded with Rob Knight (now at UCSD). I've tried almost every 'popular' diet out there, including some diets I would consider extreme (e.g., extremely low carb diet).

Each of the diets I have tried has resulted in shifts in the composition of my gut flora. Since the experiment participants equal one (me), the data are limited. That said, it has been a useful experiment in helping me understand how diet (and other lifestyle choices) impact our gut flora.

Studies have shown that the food we eat can shift the microbiome within a very short period of time. From your own personal experience, do you feel this is true and how quickly do you feel a person can alter his microbiome?
In my experience, I can shift my gut flora very quickly, in 24-72 hours.

You are an advocate for the consumption of fiber. Will you tell us why you feel it is an important part of our diet as well as how much and what kind of fiber we should consume daily? 
While all foods have the potential to impact the composition of our gut flora, dietary fiber from plants seem to be especially interesting.

Since fiber is not food for us, but rather food for our microbes deep in our bowels, changing the quantity and diversity of fiber in one’s diet has a significant impact regardless of the other macronutrients in the diet.

I always suggest that people increase the diversity and quantity of fiber in their diet and shoot for 25-30 different species of plants every week and strive for 30-150 g/day. While every day doesn't need to be 'fiber heavy,' including a few more fiber-rich plants a few days a week 'might' be beneficial.

Will you share with us the objectives and the latest developments of the Human Food Project and the American Gut Project?
The Human Food Project is headed back to Africa a few times in 2016 and now Mongolia—where we will be sampling the famous reindeer herders of northern Mongolia. This population is of interest as they consume very few plants. We will also be publishing our first 3 years of research among the Hadza in 2016.

The American Gut project—which I co-founded with Rob Knight in 2012—has now officially moved to UCSD from University of Colorado-Boulder. To date, we have received samples from more than 15,000 participants from around the world and sequenced 6,000 of those samples.

While I can't discuss the results to date in too much detail (results to be published later in 2016), I can say we have found some fascinating patterns with regard to diet and lifestyle choices of the participants.

We thank Jeff so much for his time and look forward to hearing more about the cutting-edge research being led by both the Human Food Project and the American Gut Project. You can find more information on Jeff and both of these fascinating projects by visiting


Dana Rutscher is the Practitioner Relations Manager at Hyperbiotics and possesses a vast and ever-expanding wealth of microbial health knowledge. With a graduate degree from Baylor University and a passion for helping others, Dana incorporates her enthusiasm for health and scientific discoveries into her professional pursuits and parenting. For more ideas on how you can maximize wellness and benefit from the power of probiotics, be sure to subscribe to our newsletter.