This is Your Gut on Potatoes

Several research papers have suggested that a “simplified fiber” diet will create more diversity in gut flora than a diet filled with various fiber types.

This is your gut.
This is your gut on the Potato Diet!


Diversity in any ecosystem is considered to be a desirable trait. “Plant diversity and ecosystem productivity: Theoretical considerations” is a mathematical look at ecosystem diversity that tackles a tough question:

The functioning of ecosystems has long been known to depend on the identities of the species the ecosystems contain, and hypothesized to depend on the number of species. However, recent work, plus early observations by Darwin, have left open two major questions: Are effects of biodiversity on ecosystems the logical outcome of fundamental ecological processes, such as interspecific competition for resources, or must deeper explanations be sought? And, what are the potential impacts of the rapid increases in global extinctions and of the extreme simplifications of human-dominated ecosystems on ecosystem functioning?

Through some ingenious equations, they predict what most of us know intuitively, that any ecosystem with more species present is better for everyone involved…the land, the animals, the plants, the microbial populations.

This same pattern also holds true in the inner workings of our gut.

The more we discover about our relationship with these microbial communities and their role in human health, the more it seems that we are a biological community living as a collective, an ecosystem of organisms. In this paradigm, health is seen as an expression of ecosystem diversity, resiliency and balance. Consider the implications. If who we are biologically is a collective ecosystem, what does that
imply for us psychologically and culturally?

In the human gut, a simplified flora is one that lacks diversity. This is a gut that can become dominated by pathogens. From another great paper on diversity of the human gut, see “Ending the War Metaphor: The Changing Agenda for Unraveling the Host-Microbe Relationship.”

Diversity is generally thought to be desirable for ecosystem stability (Mc-Cann, 2000). One important way diversity can confer resilience is through a wide
repertoire of responses to stress (referred to as the insurance hypothesis.

And also from the same paper, something to make you think:

The human gut is faced with a paradox: How can functional redundancy be
maintained in a system with low diversity (few divisions of bacteria), and how can such a system withstand selective sweeps in the form of, for example, phage attacks? The estimated 1,200 viral genotypes in human feces suggest that a phage attack is a powerful shaper of the gut’s microbial genetic landscape. Enough diversity of genome and transcriptome must be represented at the subspecies level to lend resilience to the gut ecosystem.

And from Eshel Ben-Jacob et al.:

Many bacterial species are extremely good at steering between survival and growth and in generating a huge diversity of behaviours in the individual bacteria that constitute a population.

Loss of Diversity

What creates this loss of diversity?

  • Antibiotic use
  • C-section birth
  • Formula feeding over breast feeding
  • Low fiber diets
  • Loss of “higher life” in the gut (ie. yeast, helminths)
  • Too many food choices

Basically, just being a human and living in 2016 you are exposed to a lifetime of diversity killers. And this brings me to the topic of today’s blog post.

The Potato Hack

Surely if you have been around here for very long, you know that I kind of got my start on the internet with talk of a quick weight-loss scheme known as “the potato hack.” It was modeled after an 1849 journal article and several historical precedents that indicated people could cure their digestive health by eating only potatoes for a week or so, or even indefinitely as some have suggested. I have always been amazed at the popularity of the potato diet when groups of people try it.  Almost universal weight loss of around 1-2 pounds per day with few reports of weight re-bound, and more reports of continued weight loss after-the-fact.

I had always assumed that the potato diet was probably hard on the gut flora, leading to a simplification in diversity, and maybe that was part of the effectiveness of the potato diet.  The potato diet is extremely high in resistant starch (types 2 and 3), up to several hundred grams per day, in fact!  To see first-hand what the potato diet does to the gut flora, I sampled my gut bacteria through uBiome, and just recently got the results.

This is your gut:

I have here two samples from uBiome, one from 2014 when I was eating my normal diet and getting 50+ grams of fiber and RS from real foods, no supplements (“Real Food” chart). I was going for the heavy-hitters: raw potatoes, green plantains, dandelions, onions, garlic, nuts, legumes, and whole grains (ie. quinoa, rice, oatmeal). My uBiome report from this dietary intervention was quite impressive. High levels of beneficial microbes and great diversity. We looked at this report a few months back, please have a look for a refresher. I think I demonstrated that a diet filled with high numbers of diverse fibers led to a gut report that was filled with the hallmarks of a “good gut.”

Note: The “diversity score” shown below is developed by MG-Rast, a metagenomic analysis server.
“Alpha diversity summarizes the diversity of organisms in a sample with a single number. The alpha diversity of annotated samples can be estimated from the distribution of the species-level annotations. Annotated species richness is the number of distinct species annotations in the combined MG-RAST dataset. Shannon diversity is an abundance-weighted average of the logarithm of the relative abundances of annotated species. The species-level annotations are from all the annotation source databases used by MG-RAST.”

MG-Rast derived chart and diversity score

This is your gut on potatoes:

I seriously thought that the uBiome report after a week of potatoes would come back looking like a desert wasteland. But true to the predictions of many, the diversity shown in this particular test was “through the roof.”

MG-rast derived chart and diversity score

The chart below is my gut a month after the potato hack while eating a normal “paleo”
diet supplemented with a blend of fibers (inulin, PHGG, pectin, RPS, wheat dextrin, and XOS).

MG-rast derived chart and diversity score

Here is a chart showing the relative abundance of some of the bacteria normally seen as the “ones to watch” in terms of gut health:

High Fiber/Real
Potato Diet
Fiber Supplemented Diet
Diversity: 26.112
Diversity: 38.953
Diversity: 32.264


I think the most surprising change on this chart was the Akkermansia which went from zero to 1.7% when on the potato diet, and back to zero afterwards. This was the first of seven gut tests I’ve had that showed any significant population of Akkermansia. Most tests have not detected any, or list it as .01% or less. Akkermansia is known far and wide as the “weight loss bacteria”. The potato diet is an amazing weight loss plan, even though you are gorging on potatoes.

All of my reports up until the potato diet had extremely high levels of Bifidobacteria. Most people have 1% or less. The decrease is not alarming to me, but surprising. It appears to have been displaced by equally efficacious bacteria. The appearance of Lactobacillus on the potato diet was another “first” for me. Lactobacillus is normally missing from my gut tests.


Though to be considered a complete success, we’d need several experimental clinical trials to examine the effects of the potato hack on a bigger population. How could we fool the placebo group?  “No, that’s not a potato!  That’s a pork chop.”

Short of clinical trials, if anyone is trying to heal or create a better gut and not having luck with their present diet, maybe that’s not what is needed. Possibly try a new approach. If you supplement your fibers, just stick to one source, ie. potato starch or inulin. If you are totally against supplementing your prebiotics, then instead of going whole-hog on as many fibrous plants as you can find, stick to a few simple fiber-foods: potatoes, beans, green bananas, corn, oatmeal, etc…  Try for a while to just eat one starchy, high fiber food that you enjoy on most days of the week. The stories of “meat and potatoes” people make lots of sense in light of all this. Or the Asian folks who only eat rice, paleo-Indians and their corn, Tigernut Man, and cattail munching Neanderthals. Never before in history have our gut bugs been presented a daily smorgasbord of fiber.

 Gut Reset

And how about the potato diet as a sort of “gut reset?” Maybe try a periodical potato hack just to give your gut a break and build up some great diversity. As they said way back in 1849:

Let those who have dyspepsia—and that means a multitude of ills which the American people in their luxurious habits are fast bringing upon themselves—try for a time the potato diet. We have tried it not for months, but a few days at a time—long enough to satisfy us of its good effects.


OK. So where did all this extra diversity come from? Was it clinging to the potatoes? Did it seek me out leaping from trees, dogs, and people to get in my belly? Or was it there all along…hiding in my appendix, lurking in my mucous, or just in such low numbers that uBiome’s fancy 4-channel Illumina Sequencer could not find it? My guess is a little of all of these routes.

And what happens when a person with a severely dysbiotic gut embarks on a week of potatoes? Will they see an increase in diversity or will they just make their life more miserable? Only one way to find out.

The other possibility here is that this is all just BS and a colossal waste of time! Maybe these numbers and reports mean very little in the grand scheme of things. Maybe it’s the “genome and transcriptome” of the bacteria present that makes all the difference (but could a colon filled with Salmonella ever be good?).

This experiment showed me that the potato hack maybe has some magic after all. And that there is more than one road to gut health. It’s up to you to find the right path and you owe it to yourself to keep trying.

Hack on!

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