How Hard Training Disrupts Your Gut

G'day mate!

Just wrapped two of the most satisfying weeks I've had. NYC HYROX is in the books. Fastest doubles time I've run, and I can already see where the next chunk comes from. The Knicks are in the Finals and I'm going to Game 4.

But something else is on my mind. In the 48 hours after HYROX, all I wanted was real food. Not powder. Not bars. Kimchi. Miso. Good yoghurt. Sourdough. My body was telling me something, and this issue is what it was saying.

In this week’s newsletter (4 min read): 
🦠 Why your gut takes a hit during hard training blocks, and what to do about it
🧪 The fermentation science that actually moves the performance needle
🍲 How I build fermented foods into my day without overthinking it

If you have a mate living on protein powder and bars through every hard block, send them THIS link.

This Isn't a Wellness Trend. It's 10,000 Years Old.

Before fridges existed, fermentation was the technology. Every culture on the planet worked out how to use bacteria, yeast, and time to preserve food, and stumbled onto one of the most powerful nutrition tools we've got.

Kimchi, miso, kefir, sauerkraut, tempeh, sourdough, natural yoghurt. Wellness brands didn't invent any of it. Humans have eaten these for thousands of years. The science is only now catching up.

The mechanism is simple. Fermentation puts live bacteria and yeast into food, and they break it down before you eat it. Your gut gets something pre-processed: more bioavailable, less inflammatory, easier to absorb.

Your microbiome is the roughly 38 trillion microorganisms in your gut. It runs digestion, immune function, inflammation, even mood. Around 90% of your serotonin is made down there. So when it gets disrupted, the fallout isn't just digestive.

What Happens to Your Gut When You Push Hard

I've noticed the same thing across every serious block. The closer I get to the pointy end, the simpler my food gets. And the simpler it gets, the more I'm quietly wrecking my gut.

Pre-HYROX you avoid anything fibrous or fermented. Nothing should disturb gut motility on race day. Right call. But you've starved your microbiome for days, and then the event piles stress on top:

• Hard training spikes gut permeability. Bacterial byproducts cross into circulation, adding an inflammatory load on top of muscle damage.

• Heavy blocks lower microbiome diversity. Your recovery budget ends up fighting on two fronts.

• Fermented food speeds the bounce-back. Intake tracks with a faster return to baseline after an event.

So after HYROX, the craving for kimchi isn't random. Your body knows what it needs.

Fiber First, Fermentation Always

I don't think "fermented foods" when I think recovery. I think fiber. I'm chasing 34g a day, non-negotiable. Fiber feeds the bacteria you're trying to grow in the first place. Fermentation without fiber is planting a seed and never watering it.

Where I've landed is less about optimisation, more about habit. Integration over addition. Not a separate fermented food moment:

• Miso into the base of whatever broth I'm making

• Kimchi alongside whatever protein's already happening

• A spoon of yoghurt where I'd usually skip it

It sticks because it's not a new habit. It's a tweak to one I already have.

A 2021 Stanford study put people on six servings of fermented food a day for 10 weeks. Microbiome diversity went up, inflammatory proteins went down, including IL-6, which runs high in hard-training athletes. A matched high-fiber diet didn't move diversity the same way. You want both, but ferments do something fiber alone doesn't.

What to Actually Do

1. Anchor one ferment a day. Not a serving of each. Pick one. Miso, kimchi, yoghurt, kefir. One daily touchpoint is sustainable. Six servings across ten foods is not.

2. Pair it with fiber. Add kimchi to a rice or grain bowl, not a protein shake.

3. Don't heat-kill it. Miso boiled into soup loses its live cultures. Stir it in off the heat. Same with yoghurt sauces.

4. Prioritise the days after. In the 48 to 72 hours after a race or hard block, your gut is in repair mode and primed to use the benefit. That's the window.

5. Make it yourself now and then. Once you know what goes into a simple kimchi, you think about the whole ingredient differently.

The Bottom Line

Fermentation is the oldest performance protocol on the planet. Every culture found it independently because the feedback loop was obvious. People who ate fermented foods recovered faster and got sick less. We just finally have the language to explain why.

The science is good. But honestly, my body knew first. Standing in the kitchen after HYROX craving kimchi, that was the signal. Learn to read those.

Recipe: Kimchi Fried Rice

This $3/serving meal is a super easy way to get fermented food into your day.

RECIPE HERE

Nutrition Breakdown:

cals: 609.2 • fat: 23.7g • protein: 29.3g • carbs: 76.7g

Quick Notes

🎬 New YouTube video is live on how to eat like an athlete for $15/day. Watch it here.

#EatGoodFeelGood

— DC