Book: The Keystone Approach - psoriasis, arthritis, and the microbiome


I’m reading a book called The Keystone Approach by Rebecca Fett. I want to start a discussion about it, because it’s full of interesting information. Ever since I was diagnosed, I’ve been looking at microbiome and diet, so I immediately bought this book when I saw it.

I hope that this thread will turn into a long analysis of ideas and specific studies referenced in the book.

Here is some information from what I’ve read so far:

A relationship between gut inflammation and severity of inflammatory arthritis:

A persuasive body of research shows that immune activation in the gut is a common feature of psoriasis and several types of inflammatory arthritis, particularly juvenile, psoriatic, and ankylosing spondylitis. Importantly, the degree of gut inflammation appears to determine the severity of these conditions.

Antibiotics and arthritis:

Researchers have found, for example, that a single course of antibiotics doubles the chance of children developing arthritis, while five or more courses of antibiotics triple the risk. It may be that antibiotics deplete the bacteria that regulate the immune system and keep harmful bacteria in check.

NSAIDs may not be good for intestinal permeability:

Medications such as nonsteroidal anti-inflammatory drugs (NSAIDs) are another major cause of increased intestinal permeability. It has been shown that medications such as Celebrex, Ibuprofen, and Aleve (naproxen) can in fact increase permeability within 24 hours of a single dose. The effect is particularly pronounced after long-term use, producing visible gut inflammation and a dramatic increase in permeability. Aspirin also increases permeability, although perhaps to a lesser extent than other NSAIDs.

The book talks about specific microorganisms from the genus Clostridium and a relationship to butyrate:

certain bacteria prompt the immune system to make more regulatory T cells by producing a short-chain fatty acid called butyrate. The bacteria that are best at producing butyrate happen to be those species found in Clostridia clusters IV and XIVa, which are often depleted in inflammatory diseases. Butyrate is thus the missing link explaining how a depletion of these microbes can contribute to inflammation. With lower levels of butyrate-producing bacteria, fewer regulatory T cells are produced, and a powerful control mechanism that typically restrains autoimmunity is compromised… As the main source of butyrate, it is unsurprising that the bacteria in Clostridia clusters IV and XIVa play an important role in maintaining the gut barrier… While many of the undesirable bacteria grow best on starch, beneficial butyrate-producing bacteria thrive on a diet rich in fiber. Consuming more fiber thus has a profound positive effect on the microbiome because it preferentially feeds the good bacteria… The various forms of fiber found in fruit and vegetables appear to have a particular advantage over fiber from grains and legumes when it comes to feeding beneficial bacteria… The bacteria that are best at feeding the butyrate-producing Clostridia are the Bifidobacteria.

This is interesting:

In one 2015 study, switching to a high-fiber, low-fat “African-style” diet for two weeks not only doubled butyrate levels in the colon but also reduced immune activation.

Bad microorganisms:

In 2016 and 2017, several studies reported that in inflammatory bowel disease, psoriasis, and arthritis, there is not only a lower level of protective bacteria but also a higher level of harmful species, such as E. coli, Salmonella, Prevotella, Collinsella, and Klebsiella. These species cause harm in two ways: firstly, they can damage the gut barrier, rendering it more permeable; secondly, they can activate the specific immune cells involved in autoimmune disease.


spondyloarthritis has been linked to a particularly aggressive form of E.coli. This type of E. coli is called “adherent-invasive E. coli” because it sticks to intestinal cells and invades the protective mucus layer, which can trigger a massive inflammatory response. It was already known that about half of all Crohn’s patients have adherent-invasive E. coli, whereas it is found in only 1 percent of the general population. In 2017, researchers found that this type of E. coli may be a major contributor to spondyloarthritis.58 (The spondyloarthritis group includes psoriatic, juvenile, and ankylosing spondylitis.)

Unfortunately, there seems to be some errors in the book too. It recommends avoiding maltodextrin (which is bad for the gut lining), but then recommends Jarrow Formula probiotics, which contain maltodextrin. I bought a different probiotic that contains similar organisms, but don’t know if it contains the right ones.

The most effective probiotic product is likely to be a combination of Bifidobacteria species, particularly one containing B. breve and B. longum. One of the best choices is Jarrow Formulas’ Bifidus Balance…

I’m going to keep this post relatively short for now, but will start a wiki-style thread where we can discuss specific recommendations from the book. I did follow some advice from the book (fish oil + olive oil, reduced starch) and noticed good results from a short experiment. I will continue to experiment with ideas from the book. I highly recommend reading it and posting some thoughts/notes here.

Welcome to the site!
Starch Diets?

I read this book almost a year ago and found it to be extremely helpful but not a homerun for my psoriatic arthritis. Not yet anyway. Before I tried her “Mediterranean” diet, I was on the Paddison Program which is a vegan diet that consists of green vegetables and you get your calories from sweet potatoes, white rice, quinoa, and buckwheat. That is Paddison’s elimination diet in a nut shell. It is mainly for rheumatoid arthritis but it was the only program that I could find so I gave it a try. I tried it for about 2-3 months and just got worse and worse with my arthritis. All of these autoimmune diets have one thing in common. They all recommend getting as much green leafy vegetables as possible. But you aren’t going to survive on green leafs alone. The trick is to figure out where to get your safe calories, i.e. starches?, healthy fats?, pseudo grains?, fruit?, kefir?, healthy meats? It took me months and months to figure out that I could not handle pseudo grains, carrots, or sweet potatoes. My spine, feet and ankles would get worse. So I have deducted that starches and pseudo grains were out. So I was done with the Paddison Program and gave the Keystone Approach a try. I found that you cannot overdo the oils. Even olive oil or any “healthy” oil can be inflammatory for some people. I try to go very very easy on olive oil. I tried a keto version of the Keystone approach using olive oil, lots and lots of olive oil and my arthritis did’t like it. I am still experiencing with the Keystone approach but this go around, I am adding a kefir yogurt which has no sugar, super low carb, and the calories come from fat. It happens to have a bunch of bifido bacteria. So I am taking a risk with the “dairy” but seem to be doing ok on it as far as I know.
I have been on and off Humira for the past year and have had to suspend it for the past 3 months due to getting a staph infection inside my nasal passages. Humira will f**K you up. I’m on my 6th antibiotic and still not any better. So much for healing my gut.
I do recommend people try her elimination diet and if it doesn’t work, try the Paddison Program. Two very different diets but trying them will help you know what food types cause problems.

One last thing, Rebecca recommends coffee. I have been off coffee for the past two years per the Paddison Program thinking it was causing my body to be more acidic but I started drinking it again and I think it is actually helping me. I do at least 2 cups a day and feel fine, maybe better actually.


Sorry to hear about the Humira experience, and hope it gets better soon. I recently started taking it and hope that I can avoid the worst of the side effects. It was either that or another biologic. There aren’t any other options for me at the moment. Things are improving so far.