The Enzyme Eating Your NAD+: Why CD38 Is the Piece Every NAD+ Protocol Misses

Here is the conversation almost nobody in the longevity space is having. Everyone is obsessed with topping up NAD+. NMN, NR, niacin, IV drips, the lot. And the assumption underneath all of it is the same: NAD+ falls as we age, so we pour more precursor in and refill the tank.

But a tank that empties faster than you can fill it is not a supply problem. It is a leak. And one of the biggest names on that leak is CD38.

What CD38 actually is

CD38 is a multifunctional enzyme and immune-signalling molecule, often found on the surface of immune cells. One of its key jobs is to break down NAD+, and it can also metabolise NMN, one of the important NAD+ precursors, which means it directly influences how well NAD-replacement strategies work in the first place.

It is not the only NAD+-consuming pathway in the body. PARPs, sirtuins and others all draw on the same pool. But CD38 appears to be one of the major drivers of age-related NAD+ loss. Think of it as a tap on the side of your NAD+ tank that runs harder and harder as the decades pass.

Why this gets worse with age (and it is not random)

This is the part that reframes everything. CD38 expression goes up as we age. So a meaningful slice of your NAD+ decline is not passive under-production, it is an active, accelerating increase in destruction.

The mechanism is inflammaging. As senescent cells accumulate, they pump out the inflammatory SASP signals, and those signals recruit and activate pro-inflammatory M1-like macrophages. Those macrophages express high levels of CD38 with enhanced NADase activity. More senescent cells, more inflammation, more CD38, more NAD+ destruction. It is a self-reinforcing loop, and the work out of Eduardo Chini's lab at Mayo, along with the Covarrubias group, laid it out clearly: CD38 is required for the age-related collapse in NAD+ and mitochondrial function, partly through SIRT3-related mechanisms, and senescent cells drive the process by activating CD38+ macrophages.

So when you supplement a precursor alone, you are pouring water into a tank while the tap runs harder every year. You will see some benefit, because more substrate is more substrate. But you are working against a leak you have not addressed.

How much does the leak matter? When researchers gave aged mice a specific CD38 inhibitor, they saw a roughly 10 percent increase in median lifespan, plus improvements in endurance, exercise performance and metabolic function. That is the target. The question is how you move toward it without a pharmaceutical.

Where flavonoids come in

This is the elegant part. Some of the best-characterised natural CD38 inhibitors are flavonoids, the plant compounds most people have only ever heard described as antioxidants.

In 2013, Carlos Escande and colleagues (working with Chini and David Sinclair) screened for CD38 inhibitors and found that apigenin and quercetin both inhibit the enzyme. Not just in a test tube either, apigenin given to obese mice raised tissue NAD+ levels, lowered global protein acetylation and improved glucose and lipid handling.

So you have a class of plant compounds that appears to act on the same CD38/NAD+ preservation pathway as the experimental inhibitors, by the same mechanism, sourced from plants. They should not be assumed to match the potency, selectivity or tissue exposure of a purpose-built molecule, but they engage the right target. That is the foundation of a smarter NAD+ strategy.

Why a stack beats a single flavonoid

Here is the reasoning behind building a flavonoid cluster rather than betting on one compound.

Apigenin and quercetin carry the strongest direct CD38-inhibition evidence. They are the workhorses of the preservation side. They slow the tap.

Quercetin earns its place twice over. It is also one half of the original dasatinib-plus-quercetin senolytic combination, meaning it contributes to clearing the very senescent cells that drive CD38 expression in the first place. So it is not only closing the tap, it is going after the upstream cause that opened it. That dual action is exactly the kind of leverage you want in a longevity formula.

Rutin is a quercetin glycoside, quercetin with a sugar attached. It is best framed as vascular and anti-inflammatory flavonoid support and as part of the broader quercetin family, rather than as a proven direct CD38 inhibitor in humans.

EGCG, the green tea catechin, rounds the cluster out. Its strength is in the surrounding terrain, modulating inflammation and senescence-associated pathways that feed the CD38 loop, rather than acting purely as a CD38 inhibitor.

The point is systems-level. You are not just inhibiting one enzyme. You are addressing the senescence that drives it, the inflammation that amplifies it, and the enzyme activity itself, from several angles at once.

Where I will be straight with you

I am not going to oversell this, because the people reading my work can smell hype.

Most of the direct CD38-inhibition data is in vitro and in mouse models. The human supplement-dose evidence specifically for CD38 inhibition is still thin, and flavonoid bioavailability is a genuine open question. Quercetin in particular has poor water solubility, GI instability and significant first-pass metabolism, so the concentrations that inhibit CD38 in a dish are not trivially easy to reach in human tissue with an oral dose. Anyone claiming a flavonoid capsule definitively slashes your CD38 activity in vivo is getting ahead of the data.

And as with all concentrated polyphenol extracts, dose and context matter, particularly with high-dose EGCG and green tea catechins, where liver safety is worth respecting rather than ignoring.

What I am confident about is the logic of the target. The biology of CD38 as a dominant driver of age-related NAD+ decline is well established. The mechanism by which these flavonoids act on it is well characterised. And these are compounds with deep safety records at sensible doses and a stack of other longevity-relevant benefits even setting CD38 aside. That is a very different risk-reward profile than a novel pharmaceutical. The downside is small and the mechanistic case is strong, even where the human outcome data is still being built.

The takeaway for your NAD+ strategy

Stop thinking of NAD+ as a refill problem and start thinking of it as a balance between three levers: how much you make, how much you lose, and how well you use what you have.

Precursors handle the first lever. The flavonoid CD38 cluster handles the second, the leak that nobody else is fixing. And sirtuin support handles the third, making sure the NAD+ you preserve actually gets spent on repair.

That three-lever logic, synthesis plus preservation plus utilisation, is exactly why we built NAD+ Next Gen the way we did, around a multi-pathway design rather than another single-mechanism precursor product. Refilling the tank matters. But if you are not closing the tap, you are doing the hard half of the job and skipping the clever half.

NAD+ Next Gen is coming. Most NAD+ products on the market are still fighting the wrong battle, pouring in more precursor while ignoring the enzyme that drains your levels faster every year. We built NAD+ Next Gen differently: a six-pathway formula designed to support how much NAD+ you make, how much you keep, and how well you use it. If you have read this far, you already understand why that matters. Join the waitlist to be first in line when it launches: https://shop.lisatamati.com/pages/nad-next-gen-waitlist