What Is NAD+? Why It Declines With Age and How to Replenish It

NAD⁺ is a coenzyme found in every cell in your body, and it acts like a rechargeable battery that shuttles electrons between molecules. Without it, your mitochondria — the structures that convert food into usable energy — simply can't do their job.

Think of NAD⁺ as the currency your cells spend on almost every transaction that keeps you alive: producing ATP (cellular energy), repairing damaged DNA, and regulating a class of proteins called sirtuins. Sirtuins are essentially cellular stress responders, and NAD⁺ is the fuel they run on. When sirtuins and other enzymes have enough NAD⁺ to work with, they help regulate inflammation, support metabolic efficiency, and influence how your cells respond to stress — functions that are central to healthy aging.

This is where Tally Health's NAD⁺ supplement comes in: it's formulated to help elevate NAD⁺ levels so these downstream processes — energy production, oxidative stress protection, sirtuin activity — have the fuel they need to keep running.*

Your body makes NAD⁺ through a few different biochemical pathways, drawing on dietary precursors like tryptophan and forms of vitamin B3 (niacin). It's a closed-loop system: your cells constantly synthesize NAD⁺, use it, break it down, and resynthesize it — thousands of times a day in a single cell.

The trouble is that this production-and-consumption cycle doesn't stay balanced over time. As you get older, the "consumption" side of the ledger starts winning.

Research consistently shows that NAD⁺ levels in tissues fall as we age. This isn't a single-cause story; it's the result of several converging shifts in cellular biology.

First, the enzymes responsible for making NAD⁺ become less efficient over time. Second, and perhaps more significantly, the enzymes that consume NAD⁺become more active. Your cells are burning through their NAD⁺ supply faster than they can replace it.

One of the primary NAD⁺-consuming enzymes is CD38, and its activity rises with age — largely in response to chronic, low-grade inflammation, a phenomenon researchers call "inflammaging." CD38 has been identified as a central driver of age-related NAD⁺ decline, showing that inhibiting the enzyme in mice restored NAD⁺ levels and improved metabolic function.

In other words, aging and inflammation feed each other: inflammation drives up CD38 activity, CD38 depletes NAD⁺, and lower NAD⁺ leaves sirtuins with less fuel to help regulate that same inflammation. It's a feedback loop, not a single switch.

Because NAD⁺ touches so many cellular processes, its decline doesn't show up as one symptom — it shows up as a general loss of resilience. Lower NAD⁺ availability has been associated with:

• Reduced mitochondrial efficiency, which can contribute to the fatigue many people notice creeping in with age

• Slower DNA repair, since NAD⁺ fuels the PARP enzymes responsible for fixing damaged DNA strands

• Diminished sirtuin activity, which may affect how well your cells manage metabolic and oxidative stress

• Impaired mitochondrial biogenesis, meaning your cells become slower to build fresh, functional mitochondria

None of this means your body is falling apart — it means the systems that keep your cells resilient are running on a thinner margin. That's an important distinction: aging cells aren't broken cells, they're cells operating with fewer resources to draw on.

Because NAD⁺ decline is driven by both slower production and faster consumption, supporting healthy levels means addressing both sides of that equation. A few evidence-informed approaches:

1. Exercise regularly. Both aerobic and resistance training have been shown to increase NAD⁺ levels, likely by boosting mitochondrial density and activating the enzyme NAMPT, which is rate-limiting for NAD⁺ synthesis.

2. Prioritize sleep. NAD⁺ metabolism follows a circadian rhythm, and disrupted sleep has been linked to lower NAD⁺ availability in animal studies.

3. Manage chronic inflammation. Since CD38 activity rises with inflammaging, addressing sources of chronic inflammation — diet, stress, sleep — indirectly protects your NAD⁺ pool.

4. Consider NAD+ precursor supplementation. Because dietary intake alone often can't keep pace with age-related tissue decline, many people turn to compounds like niacinamide (a form of vitamin B3) that supply the raw materials your body uses to resynthesize NAD⁺.

This is precisely the gap Tally Health's NAD⁺ supplement is designed to help close, using niacinamide to help replenish what your body is losing faster than it can rebuild.

Understanding why NAD⁺ declines in tissues is only half the picture — the more useful question is what you can actually do about it. Since production slows and consumption speeds up simultaneously as you age, supporting your NAD⁺ pool typically requires giving your cells more raw material to work with, not just protecting what you have.

Tally Health's NAD⁺ Supplement is formulated with 1,000 mg of niacinamide (vitamin B3) to help elevate NAD⁺ levels and fuel the cellular functions that depend on them — energy production, oxidative stress protection, mitochondrial function, and sirtuin activity.* It's gluten-free, vegan, non-GMO, and free from the nine major allergens.

See what your biological age says about your cellular energy — explore the NAD+ Supplement.