Fix the Wall First: Why "Eat More Fiber and Variety" Can Backfire When Your Gut Is Leaking

7 days ago

9 min read

Centenarian Savage · By Travis Calanoc, "Professor Savage" (NASM, NESTA, CHEK; founder of CMMAC)

Watch the video: Gut Wall Defense on YouTube

Disclosure: I partner with Legion Athletics, Equip Foods and DoNotAge, and I may earn a commission if you buy through the links or codes in this post. Partner products are held to the same evidence standard as everything else here.

Every anti-aging gut article hands you the same prescription: eat more fiber, eat more variety. For most people, that's solid advice. But it quietly assumes something most articles never mention, which is that your gut lining is intact.

If it isn't, "eat more variety" can mean giving your immune system more things to fire at. I learned that the hard way. I'm over 40, I train BJJ, and at 40 my gut put me through the worst stretch of my adult life.

Here's what you'll get from this piece:

What your gut lining actually does, and why it matters more as you age
Why "eat more variety" can backfire when that lining is leaking
The exact order I used to fix mine, and what the research really says about each tool I used

The new science: your gut microbes are part of how you age

In April 2026, Bill Sullivan, a professor of microbiology and immunology at Indiana University, laid out the emerging case in The Conversation that the microbes in your gut help shape how you age [1]. The pattern is consistent. Older guts tend to carry less diversity and more bacteria that promote inflammation. The shift is so predictable that algorithms can estimate a person's age from their microbiome alone [1].

But some people break the pattern. Older adults who age well tend to have microbiomes that look more like a younger person's [1]. That's the opening. It suggests the aging gut isn't locked in, and that what you do shapes it.

Diet and exercise are the two biggest levers, and fiber gets most of the attention. In roundworms, mice and rats, fiber supplements improved overall health and extended lifespan by 20% to 35% [1]. In humans, a 2025 study of more than 47,000 women in the Nurses' Health Study linked higher midlife intake of fiber and high-quality carbohydrates to 6% to 37% greater odds of healthy aging [2].

Keep that in perspective. The lifespan numbers come from animals, and the human data is observational. It shows a direction, not a promise.

The part the headlines leave out: the wall

Your gut lining is a single layer of cells. Protein "gates" called tight junctions seal the gaps between those cells and decide what gets through [3].

When those gates loosen, things that should stay in your gut slip into circulation. That includes bacterial fragments and food proteins. Your immune system sees them as intruders and reacts. That reaction doesn't always stay in your gut. It can show up somewhere else entirely, including your skin.

The research connects the dots like this [3][4]:

As we age, the gut microbiome shifts.
The gut barrier can weaken.
More material leaks through.
That leakage feeds a constant, low-grade inflammation that scientists call inflammaging.

In older adults, blood markers of this leakage track with real-world decline. In 59 healthy adults aged 60 to 89, higher levels of one leak marker (LBP) went with weaker grip strength and worse physical performance scores [5]. In more than 5,000 older adults followed for over 13 years, each doubling of another marker (sCD14) came with a 56% higher risk of heart failure [6].

Before you panic

None of this is automatic. When researchers compared 48 healthy adults aged 65 to 75 with 52 adults aged 18 to 40, they found no significant difference in gut permeability [7]. Their conclusion: in healthy people, the barrier's function is maintained with age.

Another study looked at three groups of older adults: people with gut symptoms, general older adults, and senior orienteering athletes, a model of healthy aging. The group with gut symptoms had significantly higher zonulin, a marker linked to a leaky gut, than both other groups [8].

The takeaway: the wall can hold as you age. Whether it does depends on you. Your history, your stressors and your habits matter more than the number of candles on the cake.

What happened to me

I turned 40 and threw a big celebration, with plenty of rich food. I already knew wheat was a problem for me. What I didn't know was how bad it could get, or how bad it had already gotten.

Then a rash showed up.

I train on the mats, so staph was the obvious suspect. It's that common in grappling. I treated it as staph, and nothing changed. It got worse.

Next I thought, maybe it's candida. So I went after it with everything I knew to fight candida. It kept getting worse. The rash spread steadily until it covered my entire body. It stopped looking like a rash and started looking like one giant sunburn, and I was in constant pain.

A friend let me use their hyperbaric chamber. It helped a little, but I still didn't know the cause.

So I finally entertained a thought I'd been avoiding: maybe this was food. I'd tried everything else. I got a blood test, an IgG food sensitivity panel (foodANALYZER). Wheat came back highest. Surprise, surprise.

But here's what floored me. Many of the other flagged foods were staples I'd been eating to fight the candida. My fixes were feeding the fire. Everything I ate was getting past my gut wall, setting off my immune system and making every symptom worse.

During the flare. Now imagine this over my entire body, with the gaps between the red patches filled in as one continuous burn.

My take: variety assumes the wall is holding

The standard advice (more variety, more fiber) assumes your gut lining is intact. If it isn't, every new food is one more thing hitting a leaky gate. More variety means more material slipping through, and more immune reactions you're getting hit with.

Once the wall is repaired, variety works the way the research says it should. That's been my experience. So the order matters:

Find the triggers → pull them → rebuild the wall → bring the variety back.

"Wait, isn't fiber good for you?"

Yes, for most people it is. But "fiber" isn't one thing. Inulin is a common fiber added to many "gut health" products. In mice with colitis, it made inflammation worse. In a subset of people with inflammatory bowel disease, the same family of fibers set off an inflammatory response [9].

That evidence comes mostly from mice and people with IBD, so it isn't a reason to fear fiber. It's a reason to sequence it. I'm not saying skip fiber forever. I'm saying repair the wall first.

The order I followed

Test first, while the gut is still reactive. My reasoning: test before you start healing, so reactions don't get masked as the lining recovers. I used an IgG food sensitivity panel. Be clear-eyed about what that test is. Allergy experts don't consider IgG results diagnostic, because IgG can simply reflect foods you eat often [10]. That may be exactly why so many of my staples lit up. I treated the panel as a list of suspects, not a verdict. The elimination and reintroduction in steps 2 and 4 were the real test. If you suspect a true allergy, see an allergist for proper allergy (IgE) testing.
Pull every trigger. If it was flagged, it was out. I kept my plate simple, whole and mostly green.
Rebuild the wall. This is where the supplements came in (next section).
Reintroduce one food at a time, every three to four days. Anything that still caused a reaction went into what I call the 90-day holding cell. After 90 days I'd try it again to see whether my gut lining could now handle it, or whether it was something to take to an allergist.

What I used, and what the evidence actually says

My rebuild stack was glutamine, bovine colostrum, creatine and several probiotics. I'm not going to oversell any of it. Here's what the research shows for each one, including where it pushes back.

Glutamine: dose-dependent at best

A 2024 meta-analysis of randomized trials found no overall effect of glutamine on gut permeability [11]. The signal appeared only in a subgroup: doses above 30 grams a day, in trials that lasted less than two weeks. Most of those trials were in hospital patients (Crohn's disease, HIV, cancer), not healthy athletes.

Bottom line: if glutamine helps, it looks dose-dependent, and 30+ grams a day is a big dose. That's a conversation for your clinician, not a scoop you guess at.

Bovine colostrum: promising, not settled

In a small trial of 12 volunteers, heavy exercise raised gut permeability 2.5-fold on placebo. Colostrum cut that rise by about 80% [12]. A later meta-analysis also found lower permeability overall, but results varied widely from study to study [13]. And one eight-week study of 30 runners taking 60 grams a day found the opposite: permeability went up more in the colostrum group than with whey or no supplement [14].

Bottom line: promising, especially around hard training, but mixed. It seemed to help me. That's one data point, not proof.

Probiotics: strain-specific

At one point we suspected an eczema-type component, which is why probiotics came in. In adults with atopic dermatitis (eczema), meta-analyses find that certain probiotics can modestly reduce skin symptoms [15]. The effect depends on the strain, the person and how long you take them.

Bottom line: "a probiotic" isn't a treatment. The specific strain is what matters.

Creatine: early, mostly mechanistic

Creatine is famous for strength, but your gut cells use it for energy too. In mice, creatine helped protect against colitis and supported the gut barrier [16]. In people with IBD, the transporter that moves creatine into gut cells is reduced, and lab work ties it to barrier integrity [17].

Here's why it made sense for me: hard training stresses the gut lining. A meta-analysis of 34 studies found that a single bout of exercise increases gut damage and permeability in healthy people, and the damage is worse in the heat [18]. I train hard, often, in South Florida. That's the mechanism I was targeting.

Bottom line: plausible and low-risk for most people, but the gut-barrier evidence in humans is still early.

The products I used

Creatine + HMB: Legion Athletics, code PROFSAVAGE ([affiliate link])
Bovine colostrum: Equip Foods ([affiliate link / code])
Longevity stack: DoNotAge, code PROFSAVAGE ([affiliate link])

These are partner products (see the disclosure at the top). The research above is about the ingredients, not any one brand.

Where I am now

My skin cleared slowly, over months, not days. I'm now heading into my fourth year, and I get very few outbreaks. My skin looks normal again.

Same spot today.

The mistakes I made, so you don't have to

Treating a skin problem as only skin-deep. If your normal skincare does nothing or makes the rash worse, look deeper.
Guessing in sequence. Staph, then candida, then something else. Every wrong guess cost me weeks and made things worse.
Adding "healthy" foods to an inflamed gut. The foods I added to fight candida were among the ones my body was reacting to.
Thinking a bigger supplement stack is the answer. Supplements supported the rebuild. Removing the triggers did the heavy lifting.

If this sounds like you

Don't guess like I did. Get checked by a doctor, and ask about a GI specialist or an allergist. Bring your symptom timeline and a food log.

This is my experience, not medical advice. Talk to a qualified healthcare provider before changing your diet or starting supplements.