Almost everyone treats NAD+ like a fuel tank. It empties as you get older, so you refill it. Simple.

That model is half right. The missing half is why two people the same age, on the same dose, end up in completely different places.

This has nothing to do with how much you train. It is about how fast your body is tearing down the NAD+ you already have.

Before the argument, the basics. NAD+ is not a stimulant and it is not a hormone. It is a helper molecule your cells cannot run without.

That last point is the one to hold onto for the rest of this.

This part is not in dispute. Researchers measured NAD+ in human skin tissue from newborns all the way up to age 77, and NAD+ went down as age went up, in both men and women.

The decline is real. The question almost everyone skips is why.

The story you have heard is that production slows down. Your body makes less of it, so you supply more.

The story you have not heard is that consumption goes up. Something is destroying it faster than it used to.

A tank that empties faster is a completely different problem than a tank that fills slower. Different problem, different fix.

There is an enzyme on the surface of your cells called CD38, and its job is to break NAD+ apart. It is the main NAD+ consuming enzyme in the body, and both its levels and its activity climb as you get older.

Then there is the detail that should stop you.

More than 90% of its activity faces outward, into the space around the cell instead of inside it.

That matters more than it sounds, because CD38 does not only break down NAD+ itself. It also breaks down the two building blocks your body makes NAD+ from, NMN and NR, before they ever get carried into the cell.

The checkpoint is not deep inside you. It is sitting on the outside surface of your cells.

Here is where it stops being about your age and starts being about your condition.

CD38 sits mostly on immune cells, and it responds to inflammation. Two 2020 papers in Nature Metabolism reached the same answer from different directions.

Inflammation raises CD38 and lowers NAD+. Immune cells loaded with CD38 collect in visceral fat and the liver as you age. Worn out cells that have stopped dividing release the inflammatory signals that pull those immune cells in and load them with even more of it.

Then the finding that matters most. Clear those worn out cells in the lab and CD38 drops, with part of the NAD+ decline reversing.

Read that again. Part of the loss reversed without adding a single molecule of NAD+.

NAD+, NMN and NR all still do their job. Nothing here argues against any of them. It argues for running two sides at once instead of one.

The supply side. What most of you are already doing.

The drain side. What almost nobody is doing.

Two people can run the identical NAD+ protocol. The one carrying less inflammation keeps more of it.

Most people run NAD+ for energy. That is the smallest thing on the list.

NAD+ is the only substrate for the enzyme that repairs damaged DNA, and it is what the sirtuins run on. So energy is what you feel when the pool drops. Repair and signaling are what you do not feel.

That is the real case for protecting the pool instead of only topping it up.

Limitless is running their End of Summer sale right now, 15% off select favorites, and code LEE20 takes more off on top of that.

A few of the items in it sit on the drain side of what you just read, which is the half most people never work.

It ends Sunday, August 16 at 11:59 PM CST.

NAD+ drops with age, but a big part of that drop is destruction, not slower production. The enzyme doing it sits on the outside of your immune cells, climbs with inflammation, and breaks down NAD+ and its building blocks before they ever get in. Supply matters. So does the drain.

Talk soon,

Lee

Stop guessing. Start optimizing.

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