Welcome to The Weekly Dose, you beautiful bags of microbes… this week we’re going to be diving into a huge life hack for better sleep, optimising pregnancy gut health and an important lesson I learned! Enjoy!

A Gamechanger For Your Sleep!

Out of the dozens of things you could do every day for your health… steps, protein targets, cold plunges, supplements, Zone 2, fasting windows…there’s one habit I’ve come to see as disproportionately powerful:

Lower your heart rate before sleep.

It sounds almost too simple, but the physiology behind it is profound. Your Heart Rate Before Sleep (HRBS) is one of the best predictors of how quickly you fall asleep, how deep your sleep is, and how much restorative, parasympathetic-dominant recovery your body experiences overnight.

And if longevity is built on the scaffolding of good sleep, then lowering your HRBS is one of the highest-leverage interventions you can make.

Why HRBS matters so much

Around bedtime, your body needs to shift from sympathetic drive (“go mode”) to parasympathetic dominance (“rest, digest, repair”). Lowering your heart rate is the easiest way to flick that internal switch.

When your heart rate is high before bed your body stays in alert mode even when your mind feels tired and you end up with fragmented sleep, poor HRV (heart rate variability), and lower restorative sleep.

How to Measure HRBS

Two ways:

1. Manually:
   Lie on your back, relax for 60 seconds, take a few slow breaths, then count your pulse for 15 seconds and multiply by 4.
   
   

2. Wearable:
   Most smart devices will show your heart rate for the 10–15 minutes before sleep.
   
   

What’s considered “good”?
~50 bpm is excellent. Most people sit around 60–75 bpm.. myself included. My average has been 65 before bed, which explains a lot about my sleep efficiency…

So I’ve been working on it!

What’s Actually Helped My HRBS

1. Finish all food ~4 hours before bed

2. Avoid heavy foods late in the evening

3. No alcohol (This one is non-negotiable. Alcohol destroys HRV and elevates heart rate for hour)

4. Reduce blue light 60 min before bed (I’m trying but start up life is unforgiving)

5. No caffeine after 12pm (Always been strict with this)

6. Finish high-intensity exercise 4 hours before sleep 

7. 1-hour calming routine (Mine is more of a 15-minute stretching)

8. Cool, dark, quiet bedroom (The holy trinity of sleep hygiene)

9. Same bedtime every night (~9:45pm)... This one genuinely works wonders for HRV.

10. Only red lights after sunset (Haven’t tried yet, though it’s weirdly appealing)

Try just one HRBS-lowering habit tonight.

Track your heart rate for a few nights and you’ll start to notice patterns you can’t unsee.

And if you try any of these and they move the needle for you, reply and tell me. I’m always looking to steal ideas that make me sleep better!

How I’m Supporting My Wife’s Microbiome During Pregnancy 

Pregnancy is one of the few times in life where two microbiomes matter at once. There’s the maternal microbiome… shifting, adapting, expanding its immunological and metabolic duties and the developing microbiome of a tiny human who hasn’t even taken their first breath.

The science is unequivocal: The health of a baby’s microbiome begins long before birth and a huge part of that foundation depends on the mother’s gut ecosystem, diet, stress levels, and environment during pregnancy.

As a doctor and soon-to-be dad, this isn’t abstract theory for me anymore. It’s become my daily mission to support my wife through the dozens of changes happening in her body and to make sure that the environment we’re building for our child is as strong, stable, and nourished as possible.

Here’s what the research says actually matters, and exactly what we’re doing at home.

1. Prioritising a High-fibre, multi-plant diet

Pregnancy changes gut motility, hormones slow down the digestive tract, and constipation becomes almost universal. These changes reshape the maternal microbiome and not necessarily for the better.

The strongest microbiome lever is diverse fermentable fibres + plant diversity.

What we’re doing:

• Aiming for ≥25–30g fibre/day (through whole foods first).
  

• Making sure there’s colour on every plate; berries, spinach, peppers, legumes (as tolerated), herbs, seeds, nuts.
  

• Gently increasing plant variety week by week to keep the gut ecosystem fed.
  
  

My wife also takes LOAM daily because pregnancy-related appetite changes and nausea can make hitting fibre targets tough. LOAM gives her 10g of gentle prebiotic fibre from six plant sources without bloating, and it’s pregnancy-safe. It has honestly become her “gut insurance.”

2. Supporting key nutrients the microbiome loves

Some nutrients directly affect microbial balance during pregnancy:

• Choline: supports fetal brain development and gut-brain axis maturation
  

• Omega-3s (DHA): lower inflammation and help regulate gut barrier function
  

• Vitamin D: influences immune tolerance and microbial diversity
  

• Calcium & magnesium: support gut motility and smooth muscle function
  

Most prenatals under-dose choline and DHA, so we supplement these separately.

3. Reducing microbiome disruptors

The pregnancy microbiome is sensitive to environmental and lifestyle stressors.
The biggest offenders:

• Poor sleep

• High stress levels

• Ultra-processed foods

• Overuse of antibiotics (only when medically necessary)

• Sedentary lifestyle
  
  

What we’re doing:

• Evening wind-down rituals

• Daily walks (even small amounts improve microbial diversity)

• Keeping UPFs to a minimum
  

I’ve learned that supporting your partner emotionally is also supporting her microbiome. Stress hormones alter gut motility, immune signalling, and even fetal epigenetic programming.

4. Protecting the vaginal & skin microbiome

Most babies don’t get their microbial “seed moment” at birth from the gut… they get it through the birth canal, skin contact, breastfeeding, and the general microbial ecosystem of the home.

That means the vaginal microbiome matters too.

What we’re doing:

• Avoiding unnecessary fragranced washes

• Wearing breathable fabrics

• Prioritising probiotics through food

• Keeping stress low (yes, stress alters vaginal flora too)
  

5. My role (fyi this is a team sport)

Men love to think pregnancy is a spectator sport… it isn’t. You’re contributing half the firmware for your little tamagotchi!

My job is to support the environment my wife and baby are both living in:

• Cooking fibre-rich meals

• Prepping snacks she can stomach when nausea hits

• Tracking her protein intake (aiming for ~1.2 g/kg/day)

• Helping her stay hydrated

• Creating a calm, low-stress home environment

• Joining her in healthy habits so she isn’t doing this alone
  
  

Supporting the maternal microbiome is about consistency and partnership.

A healthy maternal microbiome is one of the most powerful things we can optimise for a baby’s lifelong health… shaping immune function, metabolism, allergy risk, and even brain development.

And if you’re an expecting parent reading this: you’re doing better than you think. Every small, consistent choice matters.

If you want a deep dive into prenatal nutrition, microbiome science, and how we’re preparing for fatherhood, reply to this email… I’m planning a full series!

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Things I Wish I Knew Before My 30s

If there’s one lesson I wish someone had drilled into my brain a decade earlier, it’s this:

Who you surround yourself with is not a minor detail…

Most of us grow up believing personality is something stable and self-generated. Human brains are “social organs”; they tune themselves to the people around us. Their expectations become our internal scripts and their energy becomes our default state. 

In other words… their standard becomes our ceiling.

This is the Pygmalion effect in action: people rise (or fall) to the expectations placed upon them and not just from teachers or bosses, but from friends, partners, even casual acquaintances we spend enough time with. The brain internalises the ambient standards of its environment.

And in your 30s, you really start to feel it…

One of the unexpected aches of adulthood is realising how many friendships naturally fade… not because of conflict, but because life simply moves. You change careers, cities change and your life priorities shift. 

I’ve drifted from friends I once saw every day at university and school. Some days that makes me nostalgic; it’s a micro-grief for a past life you can’t go back to.

But growing up means understanding that you don’t lose people… you evolve out of chapters.
The version of you that existed back then needed those people. The version of you now may need something different and that’s okay.

The brain is plastic… environments change us. As we step into our 30s, we become more intentional architects of our inner circle. And that inner circle, more than any book, podcast or productivity hack, determines your life trajectory.

Your social diet

Psychologically, we adopt the norms of our “reference group”; the people we see as peers. If your reference group normalises cynicism, low ambition, gossip, or stagnation, your brain calibrates itself to that frequency.

If your reference group normalises growth, curiosity, responsibility, compassion, discipline… you rise without force.

In neuroscience, this is called social priming… in behavioural science, it’s emotional contagion and philosophically, it’s simply: you become what you repeatedly witness.

One thing I’ve come to love about ageing (and yes, there are wonderful parts) is realizing that every new person can unlock a new layer in you. Someone’s generosity becomes a standard. Someone’s work ethic rewires your expectations. Someone’s creativity gives you permission to think bigger.

The best people in your life are the ones who make you a little less finished every time you interact with them.

We often say “you’re the average of the five people you spend the most time with.”
But actually, you’re the average of the expectations of those five people. So choose people who expect greatness from you.

As I enter a new decade of life, I’m not clinging to the past or trying to recreate old dynamics. I’m excited for new chapters, new friends, new teachers, new influences that will change the architecture of my mind.

👋 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! (yes I read every reply!!!)

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