Issue #28: January 26, 2026

🧬 Aging Isn’t Random. It’s Metabolic — and Immune.

By the time you’re 40, your thymus — a small organ that quietly trains your immune system — has already shrunk by more than 50%.

Most people have never heard of it.

But as Eric Verdin explains, this single organ plays a major role in how well you fight infections, respond to vaccines, control inflammation, and recover as you age.

In other words:
your immune system may be aging you faster than your muscles, joints, or skin — long before anything feels “wrong.”

This idea came from a conversation between Peter Attia and Dr. Eric Verdin, CEO of the Buck Institute for Research on Aging.

It was a long episode — nearly 80 minutes — packed with dense biology.
But the big takeaway was surprisingly simple:

Aging isn’t just wear and tear.
It’s systems slowly losing coordination.

🕊️ The Canary in the Coal Mine

Verdin describes two organs — the ovary and the thymus — as “the canary in the coal mine.”

When they start to fail, it’s not an isolated problem.
It’s an early warning sign that deeper aging processes are already underway.

These organs tend to decline early because they’re metabolically demanding, highly sensitive to hormonal and immune signals, and deeply tied to long-term system regulation. When energy balance or immune control slips, they’re often the first to show it.

Think of aging like a company where internal communication starts to break down.

Departments still exist.
People still show up to work.
But coordination slips — and performance quietly declines.

That’s what aging looks like before symptoms appear.

🧠 Why Immune Aging Matters More Than You Think

Your immune system isn’t one thing.

It’s two teams working together:

The thymus is where one critical type of immune cell — T cells — is trained.

As the thymus shrinks with age, fewer new T cells are produced.
You’re forced to rely on an older, less adaptable immune system.

It’s like running a sports team with no new rookies coming in — just aging veterans.

This helps explain:

And here’s the part most people misunderstand:

Chronic inflammation does not mean a strong immune system.

In fact, it often reflects an immune system that’s overreacting to low-level threats it can’t fully clear — not one that’s primed and resilient.

That’s like having a car with the check-engine light permanently on — but no power when you step on the gas.

⚙️ Metabolism Is the Control Panel

Metabolism isn’t about weight.

It’s about how smoothly your body turns food into usable energy.

When that process becomes inefficient — especially with sugar — your body has to work harder than it should, over and over again.

That constant strain slowly wears cells down faster, even if routine bloodwork looks “fine.”

Think of it like revving your engine at every red light.

Nothing breaks immediately.
But over time, parts wear out faster than they should.

This is why surface-level metrics can be misleading.
Two people can look similar on paper — or on a scale — and still be aging very differently on the inside.

🧪 Where NAD Fits (And Where It Doesn’t)

You’ve probably heard about NAD.

Not because it’s a miracle molecule — but because it’s become shorthand for “anti-aging” in wellness culture.

In reality, declining NAD mostly reflects stress inside the system — particularly from immune activation and metabolic strain.

It’s more like a dashboard warning light than a repair tool.

Trying to boost NAD without fixing what’s causing the strain is like topping off oil while ignoring engine damage.

Useful information.
Not a shortcut.

🏃‍♂️ What Actually Slows Aging at the System Level

The most effective longevity tools aren’t exotic.

They’re boring — and powerful.

Exercise also appears to help clear out older, dysfunctional immune cells and promote the production of newer, more functional ones — even later in life.

In many ways, it may be the most effective immune-supporting intervention we have.

No infusions required.

🧭 Aging Clocks: Helpful, But Incomplete

Biological age tests are getting better.

But aging isn’t one number.
It’s organ-specific, context-dependent, and constantly changing.

An immune system can age faster than muscles.
Metabolism can lag behind strength.
One score can’t capture that complexity any more than one weather report can describe an entire city.

This is why longevity care will increasingly need to be personalized — not in the sense of chasing hacks, but in understanding which systems are aging fastest for a given person.

🧠 The Real Takeaway

Aging doesn’t start with wrinkles or joint pain.

It starts quietly — in metabolism, in immunity, in systems losing efficiency long before symptoms show up.

If you want to age well, focus less on hacks…
and more on keeping your systems working together.

That’s where longevity actually lives.

TL:DR

Until next week. Stay vital.

-Jordan Slotopolsky

📚 Sources & Further Reading