Nick Norwitz MD PhD

GHK-Cu might be the weirdest peptide in existence. And I bet nobody’s ever told you how it really works.

Deep dive here: open.substack.com/pub/staycuriousmetabolism/p/ghk-…

Consider this: Copper is an element that’s essential for human biology. It sits at the core of enzymes involved in collagen production + antioxidant defenses+ mitochondrial metabolism.

And naturally, GHK-Cu levels decline with age, falling by over 50% between ages 20 and 60.

But here’s the catch: You can’t just give the body free copper. Free copper ions can accelerate oxidative stress and cellular aging.

So, on one hand, you need copper for proper metabolic health and longevity… but on the other hand, excess free copper can actually promote aging.

GHK-Cu appears to solve this problem.

The GHK tripeptide acts as a molecular chaperone: basically a cage that safely carries copper around the body.

Then it delivers copper directly into cells. GHK-Cu binds receptors, gets internalized into little cellular compartments, and the acidity inside those compartments releases the copper exactly where it’s needed.

The result: improved collagen synthesis + better antioxidant activity + enhanced mitochondrial function

But it gets even stranger. GHK-Cu doesn’t just affect one pathway. Some analyses suggest it changes gene expression across more than 30% of the human genome.

This behaves less like a conventional hormone and more like a hand on the master control console of cellular physiology and aging itself.

In controlled human trials, topical GHK-Cu has been shown to:
Improve wrinkles
Increase skin elasticity
Improve wound healing

Injectable GHK-Cu is now also becoming increasingly popular, although that definitely extends beyond the strongest human clinical evidence.

It’s a fascinating molecule: strange biology, compelling mechanistic data, and potentially enormous promise.

If you want the full deep dive: Mechanisms + Human trials + Dosing protocols + What people are actually experiencing with GHK-Cu, check out the deep dive linked above.

#Copperpeptide #peptides #GHKCU #metabolism #skinhealth #staycurious

1 day ago | [YT] | 296

Nick Norwitz MD PhD

How to Reboot Your Body’s Batteries

Deep dive here: open.substack.com/pub/staycuriousmetabolism/p/how-…

Mitochondria are often called the “powerhouse of the cell,” as if they’re just little batteries.

But they’re so much more. They’re living, fluctuating, even dancing signaling networks that determine how your body generates energy — and even how you age.

For example, one striking feature of supercentenarians, including the woman who lived to 117, is remarkably robust and youthful mitochondria.

But the amazing thing about mitochondria is that unlike a battery or car engine, they can recover, heal, and renew themselves.

And you can help them do this: through how you live, how you eat, how you sleep, and potentially through cutting-edge mitochondrial peptides.

In today’s deep dive, we discuss How to Reboot Your Mitochondria, including:
The role of light in preserving mitochondrial health
The foundational role of mitochondria in inflammatory disease
The exciting peptides being explored for mitochondrial health and performance medicine

What the future of mitochondrial medicine might look like.

Check out the deep dive linked above.

#mitochondria #exercise #metabolichealth #peptides #staycurious

3 days ago | [YT] | 441

Nick Norwitz MD PhD

There’s a common medication now attracting attention for its potential effects on cardiovascular disease, dementia risk, and even longevity.

Deep dive here: open.substack.com/pub/staycuriousmetabolism/p/coul…

It’s called Tadalafil.

Most people know it as an erectile dysfunction drug. But the biology suggests it may have far broader implications.

First, you need to understand how Tadalafil works.

It inhibits an enzyme called PDE5, which normally breaks down a signaling molecule called cGMP.

More cGMP → more smooth muscle relaxation → wider blood vessels → better blood flow.

Importantly, PDE5 is expressed throughout the body, including the blood vessels of the heart, muscles, and brain.

But what about human data?

In one placebo-controlled trial involving 32 men with elevated cardiovascular risk, Tadalafil significantly improved flow-mediated dilation, a functional measure of vascular health.

That matters because flow-mediated dilation is not some obscure laboratory number, it is a clear functional measure of vascular health and endothelial performance.

The observational data are also interesting. In one analysis involving >50 million men,

Tadalafil use was associated with:
34% lower all-cause mortality
27% lower heart attack risk
34% lower stroke risk
32% lower dementia risk

This does not prove causation. But the signal is difficult to dismiss.
In short: Tadalafil is far more biologically interesting than most people realize.
In today’s deep dive, we break down: the mechanisms + the human data + dosing strategies + safety considerations

If you want to get into the nuance with me, check out today’s StayCurious Letter linked above.

#tadalafil #hearthealth #brainhealth #longevity #metabolism #vascularhealth #staycurious

5 days ago | [YT] | 578

Nick Norwitz MD PhD

Look at this. This is clear visual evidence of a fascinating little peptide known as KPV helping heal inflamed intestinal lining.

Deep dive here: staycuriousmetabolism.substack.com/p/the-gut-heali…

Top: inflammatory bowel disease tissue: disorganized structure + inflammatory cell infiltration

Bottom: +KPV = healthy villi return!... decreased inflammation & tissue structure normalizes

You don’t need to be a pathologist to see the difference.

But how does KPV work?

KPV is a tiny peptide made of just 3 amino acids: Lysine (K) + Proline (P) + Valine (V)
KPV appears to work inside cells by suppressing inflammatory signaling pathways (NF-kB and ERK/p38).

But here’s where it gets cooler: KPV behaves almost like an anti-inflammatory smart missile.

KPV enters gut and immune cells through a transporter called PEPT1.

Now here’s the fascinating part: The more inflamed gut tissue becomes, the more PEPT1 the cells express. And that means: → more KPV gets transported into the inflamed tissue. So KPV may preferentially target the exact tissue where inflammation is highest.

In other words: Inflammation itself may help direct the anti-inflammatory peptide to where it’s most needed.

Early evidence also suggests KPV may help protect against inflammation-associated colon cancer.

Also notable: KPV was recently removed from the FDA Category 2 peptide list, which had restricted compounding-pharmacy preparation.

As a result, interest in KPV as a gut-healing peptide has been growing rapidly in metabolic health and peptide communities.

But this is just the high-level overview.

In the full deep dive, I cover: More data + Dosing protocols + Stacking KPV with other gut-healing peptides.

Check out the deep dive on KPV, linked above.

#KPV #peptides #guthealth #staycurious #inflammation

1 week ago | [YT] | 575

Nick Norwitz MD PhD

What do you do if your GLP-1 stops working? Or maybe it never worked all that well in the first place?

Deep dive here: open.substack.com/pub/staycuriousmetabolism/p/what…

Let’s start with the fact that there is enormous variation in how people respond to GLP-1 drugs.

Some people lose a ton of weight. Others lose far less. And the difference isn’t just behavioral. It’s at least partly genetic.

For example, a high-profile 2026 paper just published in Nature found that genetic variants in the GLP-1 and GIP receptors influenced both the effectiveness and side-effect profiles of these medications.

Some people lost over 25% of their body weight.
Others lost less than 5%.
The average obscures the individual.

So, what’s going on? And if you have unfavorable genetics, how can understanding the biology help you find different solutions?

In today’s StayCurious Metabolism letter, we explore:
Mechanisms behind GLP-1s, separating two distinct biological pathways

Practical solutions if you’re truly “GLP-1 resistant”

Insights and tools that can help if the benefits of a GLP-1 begin to fade

Where this field is headed, why I’m so optimistic, and why you should be too.

If you want to get into the nuance with me, check out today’s StayCurious Letter linked above.

#glp1 #peptides #staycurious #fatloss #metabolichealth

1 week ago | [YT] | 418

Nick Norwitz MD PhD

Can One Peptide Reduce Visceral Fat and Promote Longevity? 🧵

Deep dive here: staycuriousmetabolism.substack.com/p/peptides

Tesamorelin is a peptide shown in randomized controlled human trials to reduce visceral fat by ~20%.

But that may be one of its least interesting effects.

Tesamorelin is a growth hormone-releasing hormone (GHRH) analog.

Rather than supplying growth hormone directly, it nudges your pituitary to release more of your own.
That can:
Support lean muscle
Reduce visceral fat
Improve body composition

But there's more.

Growth hormone has a fascinating two-way relationship with deep sleep.
😴 Deep sleep increases growth hormone release.
🧠 Growth hormone also appears to promote deeper, more restorative sleep.

That may help explain why some people using tesamorelin report better sleep efficiency.

Here's the part that deserves way more attention:
The thymus.
It is the most underrated organs in longevity.

Recent research suggests adults with healthier thymuses have:
LOWER risk of cancer
LOWER risk of cardiovascular disease
BETTER overall survival

Even more intriguing: studies suggest stimulating the growth hormone pathway may reduce the biological age of the thymus.

This is just scratching the surface.

I've written 100,000s of words on peptides and human bioengineering.

Check out the growing library “Peptides and More.” linked above.

#Longevity #Peptides #HealthyAging #VisceralFat

1 week ago | [YT] | 327

Nick Norwitz MD PhD

Why Smart People Defend Dumb Ideas

Deep dive here: open.substack.com/pub/staycuriousmetabolism/p/why-…

After two doctorates, years in the Ivy League, and over a decade in academia, I’ve spent a lot of time thinking about a question:

Why do smart people believe obviously wrong health ideas?

In today’s letter, I explore the deeper forces that shape scientific and medical thinking:
the pseudo-hierarchy of evidence
peer review politics
the mere exposure effect
institutional incentives
and the subtle ways bad ideas become cemented into “truth.”

I walk through concrete examples from nutrition science, cardiology, and academic publishing that you will find surprising and unsettling.

This is not a letter about what to eat for breakfast.

It’s an insider’s look at how scientific narratives are formed, defended, amplified, and sometimes distorted.

One central lesson: Intelligence alone does not protect people from bad ideas. Sometimes, in the absence of humility, it simply makes people better at defending them.

If you want to get into the nuance with me, check out today’s StayCurious Letter linked above.

#ScienceCommunication #MedicalEducation #CriticalThinking #StayCurious

1 week ago | [YT] | 378

Nick Norwitz MD PhD

What happens when you fast for 7 days?
Not what I expected.

Deep dive here: open.substack.com/pub/staycuriousmetabolism/p/what…

In a remarkable study published in Nature Metabolism, researchers put 12 healthy volunteers through a 7-day water-only fast and used advanced proteomics to track 2,923 circulating proteins simultaneously.

What they found was surprising—and suggests some people may stop fasting just before many of the benefits begin.

During the first two days, the body performed a fuel switch.
Proteins involved in fat transport and ketone production surged as participants transitioned away from glucose dependence. Basic. That’s fasting 101.

But the most interesting changes hadn't started yet… The real shift didn't begin until Day 3.

Day 3 marked a biological tipping point.

Researchers observed a massive wave of protein changes that dwarfed anything seen during the first two days.

Overall, 1,034 proteins changed significantly during the 7-day fast, with most of those changes emerging after the day 3 threshold.

This included proteins linked to cardiovascular health and proteins involved in the literal structure and function of the brain, offering new insights into how prolonged fasting may help prevent—or potentially even treat—certain neurological disorders.

This wasn't just an energy shift.
It looked more like a biological software update!

But that's not even the most interesting part…

The big question is:
Can you capture some of the benefits of a 7-day fast in just 24 hours?

If you want the nuances, the specific findings, and the practical implications, check out the deep dive linked above.

#fasting #ketones #metabolichealth #staycurious

2 weeks ago | [YT] | 613

Nick Norwitz MD PhD

What is the #StayCurious difference?

Let me start at the beginning.

I basically came out of the womb obsessed with science. Ever since I was a kid, I've been fascinated by biology and the natural world. Becoming a physician-scientist by completing an MD-PhD felt like the natural path.

I thought I was made for it, like a horse was made to run.

But everything changed when I got sick.

To regain my health, I had to think differently. I had to question assumptions, dig into unfamiliar literature, and embrace ideas that many dismissed as unconventional. In doing so, I discovered something that now seems like the most obvious thing in the world...

I used to think science was a body of knowledge, a vast and ever-growing library accumulated through the scientific method, allowing humanity to innovate and solve problems.

I was wrong.

Science isn't a monument. It's a path.

It's not something we possess; it's something we practice.

And by the same token, a scientist isn't defined by a fancy piece of paper hanging on a wall. A scientist is anyone willing to show up every day with genuine curiosity, intellectual humility, and the courage to follow the evidence wherever it leads.

That's why my communities (particularly at the StayCuroius Metabolism newsletter and on YouTube) mean so much to me.

Every day, hundreds of thousands of you show up not looking for certainty or easy answers, but looking to learn. In a world flooded with health platitudes, oversimplification, paternalism, and conflicting information, you've chosen a different path.

You've chosen curiosity over certainty.

You've chosen nuance over dogma.

You've chosen exploration over ideology.

That is the StayCurious difference. It's you.

It's what makes this community different. It's what gives me hope for the future. And I truly believe it's how we're going to build healthier, happier lives—not by pretending the answers are simple, but by having the courage to wrestle with complexity together.

So thank you.

Thank you for being here. Thank you for being an early adopter of this movement. And thank you for reminding me, every single day, that the most important credential in science isn't a written on any diploma.

It's curiosity. Plain and Simple.

2 weeks ago | [YT] | 654

Nick Norwitz MD PhD

Do Statins Cause Alzheimer’s: The Uncomfortable Nuanced Truth

Deep dive here: open.substack.com/pub/staycuriousmetabolism/p/do-s…

Can statins cause Alzheimer’s disease and dementia? The honest answer is more complex than people give it credit for.

There are data suggesting statins can impair cognition. There are also data showing neutral effects, and even potentially protective effects. That contradiction requires resolution, not echo chambers.

Take a 2012 study in patients with pre-existing cognitive decline:
Removing statins for 6 weeks improved cognition
Re-challenging with statins for 6 weeks worsened cognition

Sounds alarming. But that’s not the whole story.

Many studies and meta-analyses find: no cognitive harm, neutral effects, or even potential protection against dementia

So, what’s going on? The answer likely lies in the interaction between:
The pleiotropic effects of statins and
Individual host physiology
Context matters. (Shocker)

Most Americans are metabolically unhealthy. They have endothelial dysfunction and chronic inflammation.

On THAT metabolic background, statins may improve: endothelial function, blood flow, and inflammation Potentially benefiting both heart AND brain.

But there’s a flip side. As one example, common statins like atorvastatin may inhibit Complex IV activity in mitochondria.

And impaired Complex IV activity is associated with energetic dysfunction in the brain and Alzheimer’s disease.

So, there’s a push-pull. Some benefits. Some potential costs.

My view: The more metabolically unhealthy someone is, the more likely statins are to be brain neutral or have a net brain benefit, and not through the cholesterol lowering effects.

The more metabolically healthy someone is, the more cautiously I’d approach decades of exposure.

At the end of the day, the only honest answer is that there’s a lot we still don’t know.
But there are also practical solutions, including alternatives that may have similar lipid effects while potentially protecting the brain.

If you want to get into the nuance with me, check out today’s StayCurious Letter linked above.

#brainhealth #Alzheimersdisease #longevity #statin #staycurious

2 weeks ago | [YT] | 503