What is NAD+: A vital molecule for health and longevity

The molecule your cells run on—and how to keep it steady as you age

What is NAD+? It’s the coenzyme your cells use to make energy, repair DNA, and stay resilient. This guide explains what is NAD, why levels fall, a plain NAD vs NADH refresher, how to increase NAD levels with habits and precursors, whether NAD IV therapy or NAD injections make sense, and answers “can NAD be harmful?” with real data. A recent review in Nature Aging brings the human evidence together; we translate it here in simple terms.

Most people hear about NAD+ from a gym buddy, a trainer, or a podcast on longevity. Under the buzz is a simple idea: your cells spend NAD+ all day to turn food into energy, repair DNA, and keep stress-response systems online. As the years go by, that pool shrinks. The goal isn’t a quick spike; it’s finding steady ways to support what your cells already do.

In one minute

• NAD+ powers energy production, DNA repair, and stress-response enzymes. Levels trend down with age. 
• A rise in CD38, an enzyme that consumes NAD+, is a key reason levels drop; it links aging and inflammation to the coenzymes loss. 
• Lifestyle nudges help: training supports the salvage pathway (NAMPT), sleep/circadian rhythm matters, diet supplies B3. 
• For supplements, daily precursors have the most practical human data today; in trials, NR and NMN raise blood NAD+.
• IV approaches can shift blood markers fast in research settings, but they’re clinic-bound and short-lived; a 2024 pilot found NR IV better tolerated than NAD+ IV in healthy adults.

NAD+ and NADH—quick refresher

If you’ve wondered about NAD vs NADH, here’s the short version: NAD+ accepts electrons and becomes NADH; NADH then donates those electrons to help make ATP. Cells cycle between the two constantly, so NAD vs NADH is really about balance: plenty of NAD+ available to accept electrons, and enough NADH to power energy production

Key read: Acta Physiologica explainer on the NAD+/NADH pair and cellular redox.

What NAD+ does for you

Your day runs on thousands of NAD-dependent reactions:

• Energy: fuels key mitochondrial steps that generate ATP from the food you eat.
• DNA care: provides the “currency” PARP enzymes spend during DNA repair.
• Epigenetics and stress response: sirtuins use it to fine-tune gene activity, protein quality, and mitochondrial function.

How your body makes NAD+

Your cells top up the molecule through three routes. Most tissues rely on the salvage pathway, which is why lifestyle and certain precursors make a visible difference.

Salvage (main route in many tissues)

• Recycles nicotinamide (NAM) back to NAD+ through NAMPT → NMN, then NMNATs → NAD+.
• Nicotinamide riboside (NR) joins here: NR → NMN via NR kinases (NRKs), then into NAD+.
• This route is rate-limited by NAMPT and responds to training and circadian rhythm—one reason exercise and sleep matter.

Preiss–Handler (niacin route)

• Uses nicotinic acid (NA) → NaMN → NaAD → NAD+ (via NAPRT and NMNATs).
• Clinically familiar because niacin has a long history as vitamin B3.

De novo (from tryptophan)

• Converts tryptophan through the kynurenine pathway, then merges into the NA branch.
• Slower and tightly controlled; useful for whole-body balance but not a quick lever for healthy people.

Why levels fall with age (CD38 and more)

As we get older, CD38 activity rises in several tissues. CD38 breaks down NAD+ and even degrades NMN, trimming the pool that cells rely on. In mouse and tissue studies, higher CD38 is linked to its decline and mitochondrial dysfunction; blocking or deleting CD38 preserved NAD+ and improved metabolic readouts. Human adipose data point the same way: CD38 expression is higher with age. 

Inflammation plays into this story. Senescent cells and inflammatory signals push macrophages toward a CD38-high state, which speeds NAD+ use. This is one reason lifestyle and body composition influence NAD+ biology.

Read more: understanding inflammation and aging

Habits that speed the decline

None of this is about blame; it’s about knowing the levers.

• Low activity: less stimulus for NAMPT, the rate-limiting enzyme in the main salvage pathway. 
• Chronic inflammation: extra CD38 activity from immune cells drains NAD+. 
• Circadian disruption and short sleep: the NAD+ system is tied to the body clock; erratic sleep patterns can throw it off. 
• Excess alcohol: ethanol metabolism pushes the NADH/NAD+ redox balance the wrong way and burdens liver metabolism.  

Each of these acts like a small leak in the tank. Patch a few leaks and the whole system runs better.

How to increase nad+ levels naturally

Readers ask “how to increase NAD levels?” more than anything else. Start with the basics:

Training

Regular exercise is a reliable way to support the salvage pathway. Human work shows higher muscle NAMPT in trained people, and programs in previously sedentary adults move NAMPT in the right direction over weeks. Start where you are and build. Get started with the best exercises for longevity.

Fasting and meal timing

Short fasting windows and time-restricted eating line up with the clock that drives daily NAD+ swings. Lab and human data show that fasting nudges NAMPT and related pathways. Keep it sustainable and watch total protein and micronutrient intake. Learn more about intermittent fasting here.

Dietary B3 (niacin/niacinamide)

Foods that supply vitamin B3 feed the coenzyme production. See our guide to foods that contain NAD/NAD precursors.

Sleep

Aim for a consistent sleep window. Sirtuins and NAD+ follow daily rhythms; regular timing supports those cycles. Learn more about the importance of sleep on longevity

If you’re mapping how to increase NAD levels naturally, pair training with consistent sleep and a B3-rich diet.

Supplements in context (in short)

• Vitamins NA and NAM raise NAD+ via established routes. Niacin flush is common at higher doses; very high, long-term nicotinamide can work against sirtuin-linked goals.
• Nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) are the newer precursors with the strongest human evidence for raising blood NAD+. Multiple NR trials report sustained increases; an NMN RCT in postmenopausal women with prediabetes showed gains in muscle insulin sensitivity alongside higher levels.

Want the full comparison, including emerging compounds (NRH, NMNH) and where tryptophan fits?

NAD+ Precursors: what they are, how they work, and which ones have human data

NAD IV therapy and injections: what studies say

Clinics offer NAD+ IV therapy and, more recently, NR IV. Early human pilots show that IV routes can shift blood NAD+ quickly, but comfort varies and the effect is short-lived unless you keep returning to the clinic. Emerging data suggest NR IV is better tolerated than NAD+ IV therapy in healthy adults under controlled conditions. For everyday life, most people who want support choose oral precursors with published human data.

Our position is consistent with the comparison study: oral NAD+ itself isn’t the practical choice (low absorption), while NR and NMN have clearer evidence for raising the molecule levels in people.

Can NAD be harmful? Safety snapshot

Most clinical studies so far run for weeks to months and focus on specific groups.

• NR: repeat-dose trials in middle-aged and older adults show sustained rises in whole-blood NAD+ with good tolerability.
• NMN: in a 10-week RCT, postmenopausal women with prediabetes improved muscle insulin sensitivity; safety looked acceptable in that timeframe. Larger and longer trials are in progress.
• NA/NAM: long clinical history as vitamin B3 forms. Expect flushing with niacin; keep nicotinamide within standard vitamin ranges unless guided by a clinician.

Also interesting: Top 11 longevity hacks backed by science

Where our products fit

If you want a simple, daily option, our NAD+ Booster Capsules combine NR with standard-dose NAM, feeding the main salvage pathway that most tissues use.

Still choosing between formats? Read What is NMN? and NR benefits & side effects.

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