Written by the Nuvirox Research Team
Key points
- Your cells do not store much energy. They run a continuous rebuild: a typical adult hydrolyses and regenerates on the order of 100–150 moles of ATP a day, roughly your own body weight, from a standing pool of only tens of grams.
- Almost all of that regeneration happens in mitochondria, and almost all of it depends on electron carriers — NAD+ chief among them — ferrying electrons from food to oxygen.
- Knowing the machinery does not mean you can supplement your way to more of it. Most everyday tiredness is a demand and recovery problem, not a broken ATP factory.
Short answer: your cells make energy by stripping electrons off food, passing them down a chain of proteins in the mitochondrial membrane, and using the resulting proton gradient to spin an enzyme that rebuilds ATP. The molecule that carries those electrons is NAD+, which is why it turns up in almost every conversation about cellular energy. But the honest framing matters: this system is not usually the bottleneck in ordinary tiredness. It is the substrate everything else acts on.
What is ATP, and why does the body remake so much of it?
ATP — adenosine triphosphate — is the cell’s spendable currency. Nearly every energy-requiring job, from pumping ions across a nerve membrane to sliding one muscle filament past another, is paid for by snapping a phosphate off ATP.
The striking part is the scale. Reference physiology puts daily ATP hydrolysis in the range of 100–150 moles for an adult, while the body holds only a small instantaneous pool at any moment Dunn J, Grider MH (see references). Each molecule is therefore recharged and spent over and over, many times a minute. There is no reservoir to draw down. If regeneration stops, function stops within seconds.
Where does the energy in food actually go?
Food is not burned directly into ATP. It is dismantled in stages, and the useful output of the early stages is not ATP at all — it is reduced electron carriers.
Glycolysis breaks glucose into pyruvate in the cytoplasm and nets a small amount of ATP directly. Its more important output is NADH: NAD+ that has picked up electrons. Pyruvate then enters the mitochondrion, feeds the citric acid cycle, and that cycle spins out far more NADH along with FADH2. Fat takes a different entry road — beta-oxidation — but arrives at the same place with the same currency.
How do mitochondria turn electrons into ATP?
NADH delivers its electrons to the first complex of the electron transport chain, embedded in the inner mitochondrial membrane. The electrons then move down a series of protein complexes, each at a slightly lower energy level, and finish by reducing oxygen to water. That is what the oxygen you breathe is for.
At three points along the chain, the energy released is used to pump protons out across the inner membrane. This builds an electrochemical gradient — a charged, acidified space. Protons then flow back in through ATP synthase, a rotary molecular motor, and the rotation drives the joining of ADP and phosphate back into ATP. Standard estimates put the yield around 32 ATP per glucose molecule fully oxidised.
What human studies actually show about the NAD+ link
NAD+ supply is genuinely rate-relevant, and it is not static. In human skeletal muscle biopsies from 57 people, the abundance of NAMPT — the rate-limiting enzyme in NAD+ recycling — correlated negatively with age, and twelve weeks of either aerobic or resistance training raised it in both younger and older participants. Notably, peak oxygen uptake was the strongest predictor of NAMPT levels, which points at training status rather than age alone as the lever.
Raising NAD+ in humans is achievable and measurable. The NADPARK trial gave 1,000 mg of nicotinamide riboside or placebo to 30 newly diagnosed, treatment-naive Parkinson’s patients for 30 days and detected increased NAD+ in the brain by magnetic resonance spectroscopy, along with clear shifts in the NAD metabolome in blood, muscle and cerebrospinal fluid.
The honest counterweight: more substrate is not automatically more output. A trial can raise NAD+ convincingly and still leave the clinical question open. NADPARK was a phase I study designed to prove cerebral penetration and safety, not to demonstrate that people felt or functioned better in any durable way. Across the wider literature, the gap between reliably moving a biomarker and reliably moving an outcome remains the central unresolved problem in this field, and any brand that skips over it is selling you something. We cover the specifics of that gap in our piece on whether NAD+ supplements actually raise NAD+.
What understanding the pathway won’t do
It will not tell you why you are tired. The ATP system is remarkably robust. In genuine mitochondrial disease the failure is dramatic and clinically obvious, not subtle. Ordinary day-to-day fatigue almost never traces to a shortfall of ATP synthesis capacity. It traces to sleep debt, deconditioning, iron or thyroid problems, medication effects, chronic stress load, or an untreated condition.
It also will not make the ceiling higher on its own. Your mitochondrial density and aerobic capacity respond powerfully to training and only marginally to anything you swallow. If everything feels effortful, the aerobic side of that equation is worth examining first — we walk through it in whether a low VO2 max is why everything feels hard.
Where NAD+ precursors fit, realistically
Human trials of nicotinamide riboside have generally used 250–1,000 mg per day, with 1,000 mg being the most common dose in the better-designed studies, and have run from a few weeks to several months. Blood NAD+ typically rises within days. Functional changes, where they have been observed at all, take longer and are more modest than marketing implies.
The reasonable expectation is that a precursor tops up a recycling system that declines with age and inactivity — the salvage pathway that does most of the actual work. It does not build new mitochondria for you. Training does that. If you want the deeper version of the mitochondrial side, see our overview of mitochondria supplements and what the evidence supports.
Frequently asked questions
Do cells make energy without oxygen?
Yes, but far less of it. Glycolysis can run anaerobically and yields a small amount of ATP quickly, which is why you can sprint. It regenerates NAD+ by converting pyruvate to lactate. That lactate is a fuel and a signal, not a waste product causing your soreness — a myth we unpick in our piece on lactic acid and muscle fatigue.
If ATP runs out in seconds, why don't I collapse when I skip a meal?
Because the ATP pool is being resupplied continuously from stored fuel, not from your last meal. Liver glycogen, muscle glycogen and body fat all feed the same machinery. Skipping a meal changes which fuel dominates, not whether the factory runs.
Does taking ATP as a supplement work?
Swallowed ATP does not survive digestion intact in a way that meaningfully raises cellular ATP. Cells rebuild their own from ADP continuously. Supplying precursors and cofactors is a more coherent strategy than supplying the end product.
Is NADH a better supplement than NAD+ or its precursors?
The cell manages its own NADH-to-NAD+ ratio tightly, and that ratio is a regulated signal rather than something you want to override. Precursors that feed the recycling pathway have the deeper human trial record.
How fast can I change my mitochondrial capacity?
Meaningful changes in mitochondrial enzyme activity from aerobic training show up over weeks, with a large share of the adaptation in the first six to twelve weeks. That is considerably faster than most people expect, and considerably slower than most supplements promise.
From Nuvirox
Why we formulated NAD+ Restore.
If the machinery above is the engine, NAD+ is the part of it that gets genuinely scarcer with age and inactivity. That is the narrow, defensible reason to consider a precursor at all.
- 500 mg Nicotinamide Riboside Chloride (NR) — one of the two most-researched NAD+ precursors, within the dose range used in published human trials.
- 150 mg trans-resveratrol (Japanese Knotweed) + 50 mg quercetin (Sophora japonica) — polyphenols studied alongside NAD+ pathways for cellular health support.
- 10 mg galactomannans from fenugreek — to support absorption.
- 60-day money-back guarantee — long enough to actually evaluate it the way the research says you should.
The bottom line
Cellular energy production is one of the best-understood processes in biology: food gives up electrons, NAD+ carries them, mitochondria convert their descent into a proton gradient, and ATP synthase turns that gradient back into spendable ATP, roughly a body weight of it per day. Understanding it is genuinely useful. What it does not do is diagnose your tiredness. The system is robust, and everyday fatigue is far more often about sleep, conditioning, iron, thyroid or stress than about a shortfall in ATP synthesis. Treat the biochemistry as context, not as a conclusion.
References
- Dunn J, Grider MH. Physiology, adenosine triphosphate. StatPearls. NCBI Bookshelf ID: NBK553175.
- de Guia RM, Agerholm M, Nielsen TS, et al. Aerobic and resistance exercise training reverses age-dependent decline in NAD+ salvage capacity in human skeletal muscle. Physiological Reports. 2019;7(12):e14139. PMCID: PMC6577427.
- Brakedal B, Dölle C, Riemer F, et al. The NADPARK study: a randomized phase I trial of nicotinamide riboside supplementation in Parkinson’s disease. Cell Metabolism. 2022;34(3):396-407.e6. PMID: 35235774. DOI: 10.1016/j.cmet.2022.02.001. ClinicalTrials.gov: NCT03816020.
- Nakahata Y, Sahar S, Astarita G, Kaluzova M, Sassone-Corsi P. Circadian control of the NAD+ salvage pathway by CLOCK-SIRT1. Science. 2009;324(5927):654-657. PMID: 19286518. DOI: 10.1126/science.1170803.
- Conze D, Brenner C, et al. What is really known about the effects of nicotinamide riboside supplementation in humans. PMID: 37478182.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This article is for informational purposes only and is not a substitute for professional medical advice.