Hello my friends and fellow sentient bags of microbes! This week we’re diving into the missing link in colon health, the science of optimal sleeping positions, and a few underrated life lessons I wish I’d learned before turning 30.

Why Most Modern Diets Starve Half Your Microbiome

Here’s a gut health truth almost nobody talks about: most of our bacteria live in the distal colon…the far end of your large intestine.

That’s where the densest, most diverse microbial communities set up shop. And they need fuel.

The problem is that most modern diets don’t deliver it.

The fermentation geography problem

When we do eat fiber, it’s often the kind that ferments quickly in the proximal colon (the early section). Think inulin, chicory root, or even certain fruit fibers. This isn’t a bad thing but it’s only one gear of the microbiome which is hit.

These “fast fermenters” are like fireworks…quick bursts of activity, lots of gas, and then…nothing left for the back half of the gut. That’s why so many people complain of bloating with various fiber rich foods or even generic fiber supplements.

Meanwhile, the bacteria at the end of the colon…the ones responsible for producing critical short-chain fatty acids like butyrate; are left starving.

Without enough distal fermentation, you get less butyrate, weaker gut barrier protection, less immune support, and a microbiome that slowly loses balance.

What we need instead

To truly nourish the microbiome, we need fibers that travel further down the gut.

• Fibers from foods like corn and wheat ferment slowly, trickling fuel into the middle and distal colon.
  

• Root vegetables like cassava and yuca, or even green bananas, provide resistant starches and soluble fibers that reach the far end of the gut.
  

• These “slow burners” don’t create massive gas spikes upfront; instead they provide a steady release of energy that keeps bacteria fed across the entire colon.
  

Think of it as the difference between kindling that flares up instantly versus logs that burn all night. You need both to keep the fire alive.

Practical takeaways

If you want to support your gut bacteria all the way through your colon:

• Pair fast fermenters (onions, garlic, legumes, oats, apples) with slower fibers (corn, sweet potato, wheat, cassava, green bananas).

• Swap your white rice for corn, quinoa, or barley a few times this week. Slower fermenters, better downstream coverage.

• Throw cassava or sweet potato into your meals (bake fries, mash, or roast). They’re root-based slow burners.

• Don’t peel everything. Leave the skin on potatoes, apples, or carrots when you can; the skin adds bulk and slows transit.

• Rotate fiber sources; diversity in = diversity out.

• Think beyond numbers. Hitting “30g of fiber” is good, but what type of fiber matters more for microbiome health. Aim for diversity, not just volume.

• Consistency beats intensity. A steady trickle of varied fiber every day is better than a giant “fiber bomb” once in a while.

Your microbiome isn’t just in your “gut”...it’s in your whole colon.

If you only feed the front, you’re ignoring the back half where the majority of your bacteria (and much of your health potential) actually live.

P.S. This is exactly why I’ve spent the last two years deep in research developing LOAM: a diverse blend of prebiotic fibers that cover the full spectrum…fast, medium, and slow fermenters. It’s designed to sustain fermentation all the way to the distal colon, feeding all your bacteria and boosting short-chain fatty acid production where it matters most. It’s out in just a few short weeks so if you want to get priority access (as I’m just doing a small initial run!) then join the waitlist here to guarantee a chance of getting it:

P.P.S I’ll be giving people on the waitlist some early exclusives too! ;) see you inside and can’t wait to share this with you! Oh and check out a new chia seed pudding recipe I’m trying (scroll to the end of this email).

What’s The Best Sleeping Position?

If you search online for the “best” sleep position…you’ll tumble into a rabbit hole of advice: Sleep on your left for digestion! Flat on your back for your spine! Never on your stomach…it’ll ruin your neck!

Like most health tips on the internet, there’s a kernel of truth in there, wrapped in a lot of oversimplification. So let’s break it down using what the evidence (and anatomy) actually tells us.

Left side sleeping and digestion

Your stomach sits slightly to the left, and its exit valve (the pylorus) tilts toward the right side into the small intestine. That’s why you’ll often hear that sleeping on the left aids digestion.

And in people with acid reflux or heartburn, there’s some data to support it. A study in The American Journal of Gastroenterology found that left-side sleeping reduced episodes of acid reflux compared to lying on the right. The reasoning: gravity and stomach orientation make it harder for acid to escape upwards into the oesophagus.

Actionable takeaway: If reflux or heartburn keeps you up at night, try rolling onto your left side. It won’t cure the condition, but it can reduce those annoying midnight flare-ups.

Back sleeping and spinal health

Lying on your back (the “supine” position) is often recommended by physios because it spreads body weight evenly, reducing pressure points. This can protect the neck and lower back from strain.

The flip side? (Pun very much intended.) Supine sleeping can worsen snoring and sleep apnoea, since gravity encourages the tongue and soft palate to fall backward, narrowing the airway. Research published in Sleep Medicine Reviews highlights this link clearly.

Actionable takeaway: Back sleeping can be great for spinal support but if your partner complains you snore like a faulty chainsaw, side sleeping may be kinder for both of you.

Side sleeping and pregnancy

Pregnant women are often told to favour their left side. This advice isn’t just folklore. Left-side positioning can improve blood flow to the placenta and reduce pressure on the liver. But large studies (including a review in BMJ Open) suggest that right-side sleeping is also safe.

Actionable takeaway: In pregnancy, aim for whichever side feels most comfortable. Use a pillow between the knees or under the bump to ease lower back or pelvic pressure.

Stomach sleeping

Stomach sleepers…brace yourselves. This position can reduce snoring, but it’s notorious for straining the neck and compressing the lower back. Over time, it may lead to stiffness or numbness.

Actionable takeaway: If you can’t break the habit, try using a very thin pillow (or none at all) to keep your neck from being twisted at awkward angles.

So… what’s “best”?

There’s no single “optimal” position for everyone.

• If you’ve got reflux, left side may help.
  

• If you want spinal support, back sleeping can be good.
  

• If you snore or have sleep apnoea, side sleeping is safer.
  

• If you’re pregnant, pick whichever side feels best with pillows for support.
  

For the rest of us meat sacks…the best sleep position is the one that gives you uninterrupted, high-quality sleep. Sleep architecture (your cycles of deep and REM sleep) matters far more for health than whether you started the night on your left or right.

And let’s be real no matter how saintly your bedtime position, most of us wake up sprawled diagonally, one leg hanging off the bed, drool on the pillow, wondering what century it is (or maybe that’s just me lol)

Don’t obsess over “perfect” posture. Instead:

• Experiment if you have reflux, back pain, or pregnancy discomfort.
  

• Use pillows to support alignment (between the knees, under the neck, or behind the back).
  

• Prioritise comfort and sleep quality above rigid rules.
  

Because in the end, the best sleep position is the one that helps you wake up feeling human.

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Reminder: This newsletter is free, always will be and I send it out every Sunday to give you in-depth insights into the health topics!

Things I Wish I Knew Before My 30s

Reinventing yourself isn’t a crisis. 

There’s this myth that I (and many people) succumbed to that by the time you hit your late twenties, life is supposed to be…figured out. Career path mapped, friend group set, habits locked in like wet cement. 

But remember…the cement never really dries.

Your brain stays plastic well into old age. Your wiring can change. New synapses form, old ones weaken. You’re not a finished product; you’re a work in permanent beta mode.

It took me a while to figure out that my (and your) identity isn’t one big decision but the sum of repeated actions. Want to “become” healthier, kinder, more disciplined? Then start by acting like someone who is, long enough for your brain to believe its own PR.

Underrated life advice: You’re allowed to reinvent yourself as many times as you need. You can start building new habits today. Set new standards next week. Make friends with new people. Build a new career(s).

It doesn’t matter if you’ve spent five years on the “wrong” path…it only matters that you don’t spend the next five clinging to it out of pride.

Start small. Radical overnight change usually collapses under its own weight. But micro-shifts compound: one new standard, one new person, one swapped habit. Update the software while the hardware hums along.

The problem is, most people are too wrapped up in their own existential crisis to care that you’ve changed jobs, friend groups, or suddenly decided that 6 am yoga or BJJ is your new “thing.” Reinvention feels scandalous from the inside and barely noticeable from the outside.

So if you’ve been waiting for permission…here it is. You’re not stuck. You don’t have to keep playing the same role just because you once auditioned for it.

Action step

Pick one tiny thing today that your future self would be grateful for…that’s reinvention in motion.

👋 Who are you again? I’m Karan Rajan - a doctor and curious explorer of all things health and wellness. I host the Dr Karan Explores Podcast and have written two books "This Book May Save Your Life" and "This Is Vital Information" (you can pre-order it now!) and have just founded a microbiome company, LOAM Science  to create the best fiber product in the world!

Every Sunday, I share 3 interesting things about health, life and science to make your life easier, healthier and happier. (Disclaimer: I’m more your friend with health benefits. None of this is medical advice.) 

And oh, you if also feel strongly about some health things or just want to say hi? Hit reply... I’d love to hear it and hear from you!

Oh and congratulations on reading to the end…that’s a lot of science you’ve learned!  btw don’t forget to check out my new chia pudding recipe:

If you try it, let me know what you think!

Coconut macadamia chia pudding

6 tablespoons chia seeds
1.5 cups unsweetened coconut milk
0.75 teaspoon vanilla extract
1/2 teaspoon cinnamon
+ crushed macadamia
+ sea salt pinch

Mix them together, cover and chill overnight in the fridge. Feel free to thrown in some mixed nuts or a handful of your favourite berries on top!

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