NAD+: what the science actually says

NAD+: lo que dice la ciencia, sin exagerar

Illustrative image. Does not represent guaranteed results.

Start with something your body already does well, every day, without you thinking about it: it makes its own NAD+. It builds it from niacin — vitamin B3 — found in ordinary food: chicken, tuna, beef, peanuts, mushrooms, whole grains. The machinery exists, it works, and it has been working your whole life.

That part is good news and it is true. The question that follows is a different one, and it drives an entire industry: if your levels fall with age, does taking it in a capsule help?

That question does have published answers in humans. They are less enthusiastic than any advertisement you will see, and considerably more interesting. This article walks through them in order, from the 2018 trial that started everything to the 2026 study that finally asked the question that team had left open.

Here is how it ends, because we do not build suspense out of anyone's health: raising blood NAD+ works and is safe. Whether that makes you feel or function better is precisely what remains unproven.

What NAD+ is and where your body gets it

NAD+ (nicotinamide adenine dinucleotide) is a coenzyme involved in fundamental reactions of energy metabolism in practically every cell you have. Every time a cell turns food into usable energy, NAD+ is there, shuttling electrons back and forth.

It is not an exotic substance. Your body builds it from niacin, vitamin B3, which is in ordinary food: chicken breast, tuna, liver, beef, peanuts, sunflower seeds, mushrooms, whole grains. The NIH fact sheet on niacin, linked below, has the amounts.

NAD+ levels tend to decline with age. That observation is the starting point for all the scientific interest — and for all the marketing. It connects to other things that change as you age and that we cover separately: mitochondrial function, background inflammation, and more broadly what aging well actually means.

The leap worth watching

There is a line of reasoning that sounds airtight and is worth slowing down on, because it powers nearly all the advertising in this category:

• Step 1: "NAD+ levels fall with age." — This is observed.
• Step 2: "We can raise them with an oral precursor." — This is proven, and you will see the numbers below.
• Step 3: "Therefore raising them improves your health." — This is what is not settled.

All three steps need their own evidence. The first two have it. The third is where the paved road ends — and it is exactly the step the advertising skips.

What the 2018 trial actually showed

The most-cited human trial on NAD+ was published in Nature Communications in 2018, led by Christopher Martens, then at the University of Colorado Boulder. It was randomized, double-blind, placebo-controlled and crossover: two 6-week periods, with healthy middle-aged and older adults taking nicotinamide riboside (NR).

The authors' conclusion, keeping their structure: supplementation was well tolerated and effectively stimulated NAD+ metabolism. On clinical effects they wrote that their results provide initial insight, and that future clinical trials should further assess the potential benefits of NR for reducing blood pressure and arterial stiffness in this group.

"Should further assess" is not the same as "it works." That distinction was this whole article when we first wrote it. Now there is something more to report: someone went and assessed it.

Look at the last row. The trial did not measure longevity. Nobody has, in humans with this kind of design, because it would take decades of follow-up.

What happened after 2018

More human trials were published in the years that followed. They are worth reading in order, because together they tell a shaped story.

2019 — exactly how much it rises

An 8-week randomized, double-blind, placebo-controlled trial in overweight but otherwise healthy adults tested three NR doses. The result was clean and dose-dependent: 100 mg raised blood NAD+ by 22%; 300 mg by 51%; 1,000 mg by 142%. The rise appeared within the first two weeks and held for the rest of the study.

On safety: no reports of flushing — the classic effect of high-dose niacin — and no significant difference in adverse events versus placebo. It also did not raise LDL cholesterol or disturb one-carbon metabolism.

It is a good study, and it closes step 2 firmly: NR arrives, raises NAD+, and is well tolerated.

2021 — NMN in runners, and the fine print under the headline

A 6-week trial in 48 amateur runners combined training with nicotinamide mononucleotide (NMN) at three doses against placebo. The paper's headline says NMN "enhances aerobic capacity" — and it is worth reading what exactly was measured.

What did rise more than control: oxygen uptake and power at the ventilatory thresholds — the points where breathing changes gear — in the medium and high dose groups.

What did not change in any group: VO₂ max, oxygen pulse, or peak power. In other words the maximal measures — what most people mean by "aerobic capacity," and what we discuss in VO2 max and longevity — stayed where they were.

It is not a null result, but it is far narrower than the headline. And it was in people already training five or six times a week.

2022 — NMN in middle-aged adults

A 60-day multicenter trial in 80 healthy middle-aged adults compared placebo against 300, 600 and 900 mg of NMN. Blood NAD+ rose significantly in every treated group, most at 600 and 900 mg. No safety problems appeared.

On function: distance covered in the six-minute walk test increased more than placebo, and a perceived-health questionnaire score (SF-36) came out better. On the other hand HOMA-IR — the insulin-resistance index we cover in insulin resistance — showed no significant difference.

Two things have to be said, because they change how this study reads. First: several of its authors are affiliated with the companies that manufacture and sell the product. That does not invalidate it, but it is information you are entitled to have. Second: one widely quoted outcome here is a "blood biological age" calculated with an online tool, which is not a validated measure of aging.

2026 — the 2018 question, finally answered

And here is the part that makes this article exist.

In 2026, Christopher Martens — the same principal investigator as the 2018 trial — published a phase-II pilot study in Alzheimer's & Dementia: 12 weeks, randomized, double-blind, placebo-controlled, in 42 adults with amnestic mild cognitive impairment (22 on NR, 20 on placebo).

Blood NAD+ doubled in the NR group. Once again: step 2 works, no argument.

And then, the results:

• Cognitive function (the primary outcome): no improvement.
• Total cerebral blood flow: no improvement.
• Blood pressure — exactly what the 2018 trial had asked to be studied: no improvement.
• Exploratory analyses showed a possible increase in regional blood flow, particularly the hippocampus. The authors present it as something to investigate, not as a finding.

The authors' conclusion is direct enough to be worth quoting in shape: NR effectively raises NAD+ in people with mild cognitive impairment, but does not improve cognitive function, total cerebral blood flow or blood pressure over 12 weeks.

It has to be read precisely, in both directions. What this study does not say: it did not study healthy adults, but people with mild cognitive impairment. It is a pilot, with 42 people and 12 weeks. It does not prove NR "does nothing" in other populations or over longer periods.

What it does say, and this carries weight: when the team that generated the hopeful 2018 signal went looking for it with a controlled design, measuring the blood pressure they themselves had flagged, the signal did not appear. And they published it anyway. That is science working properly, and it is exactly what you will not find on a product page.

Why raising a biomarker is not enough

This is the most important point in the article, and the one most often left out.

When a substance raises a marker in your blood, it proves two things: that it arrives, and that it does something biochemically. Both are necessary. Neither proves you will feel better, function better, or live longer.

Medicine's history is full of markers that moved in the right direction while the clinical outcome failed to follow. They are called surrogate markers, and they are useful right up until someone mistakes them for the outcome.

NAD+ sits in that uncomfortable spot today: a marker we know how to move precisely, whose clinical importance remains unestablished. That is why the 2018 authors asked for more studies rather than declaring the matter settled, and why the 2026 follow-up matters so much even though its result is negative.

Why the same dose may not do the same for you

There is a rarely quoted detail that changes how to read everything above. A later analysis of the 60-day NMN trial looked at how much the response varied between people taking exactly the same dose.

Variation within a single group ran from 29% to 113%. Put plainly: on the same capsule, the same day, at the same hour, some people's NAD+ rises enormously and others' barely moves.

That explains much of the distance between enthusiastic testimonials and the modest averages in the trials. And it has an honest practical consequence: a group average does not tell you what will happen to you, and nobody can know in advance without measuring.

What actually looks after the machinery

If you have read this far, it is only fair to end on what does have backing. The good news is that none of it is exotic.

Vitamin B3 from food. Your body makes NAD+ from niacin, and niacin is in ordinary food. True deficiency is rare in anyone eating a varied diet. Before considering a precursor capsule, it is worth knowing whether the basics are covered.

Muscle and movement. The pathways that use NAD+ live largely in muscle, and muscle responds to being used. We cover it in protein and muscle and in strength training.

Sleep and steady blood sugar. Energy metabolism does not work in isolation. Sleeping badly worsens the following week's glucose (sleep and weight loss), and repeated glucose spikes leave a long-term mark (glucose spikes and aging).

None of these comes in a bottle, which is why they get promoted less. But if what you actually care about is aging better, they have more evidence behind them than any NAD+ precursor available today.

So your expectations are the right ones

If after all this you are still considering it, here is the honest framing:

• What you can expect with confidence: that your blood NAD+ will rise, and that it will be well tolerated over the periods studied.
• What you cannot expect: a noticeable, rapid effect on energy, memory or aging. The published evidence does not support that.
• What nobody knows yet: what happens with years of use. The longest trial we have cited ran 12 weeks.
• What varies: you. The response between people differs by more than twofold.

And a question that works here and anywhere else: in which study, with how many people, for how long, and measuring what? If whoever is selling it cannot answer all four, you already know something important.

Who is this NOT for?

If you expect a noticeable, rapid effect on energy or aging, the published evidence does not support that expectation. Individual results vary and are not guaranteed.

If you are pregnant or breastfeeding, or have kidney or liver disease, this requires medical evaluation first, not a purchase decision.

If you take other medications, raise it. Interactions are reviewed case by case, and it is not something a label settles.

If you are in cancer treatment, this is a conversation with your oncologist before anyone else. NAD+ metabolism participates in cellular processes that are weighed differently in that context.

And if what you are trying to fix is persistent fatigue, starting with labs makes more sense than starting with a supplement. Anemia and thyroid explain a great many cases of fatigue and are caught by cheap tests. We cover it in which labs should I ask for.

GLP-1 programs with medical oversight

At SCTS1 we run GLP-1 weight-management programs with FDA-approved medications (Wegovy®, Foundayo™, Ozempic®) from $149 a month, by telemedicine, in Spanish and English. Eligibility is determined by medical evaluation.

How it works, in the real order: once you start your program, a licensed physician reviews your case — habits, stress, sleep and medical history — and orders labs only if they consider it necessary. Not everyone needs them, and they are not an automatic requirement.

Individual results vary and are not guaranteed.

See the programs →

Frequently asked questions

Does NAD+ reverse aging?

There is no published human evidence supporting that claim. No human trial has measured longevity: it would take decades of follow-up. What has been measured is blood levels, tolerance, and some functional outcomes at 6, 8 and 12 weeks.

Does it help with energy?

The 2018 trial did not establish that as a demonstrated result, and its authors described the clinical findings as initial insight. In the 2026 study, with NAD+ doubled, cognitive function did not improve. If you have persistent fatigue, the right move is to find the cause, not to start with a supplement.

Is it safe?

In the trials cited, tolerance was good: no flushing, no more adverse events than placebo, and no rise in LDL cholesterol, over periods of 6 to 12 weeks. That is what was measured. Twelve weeks tells you nothing about years of use, and your case is assessed by a licensed physician.

What is the difference between NR and NMN?

They are two different NAD+ precursors. NR is the one in the 2018 and 2026 trials; NMN is the one in the 2021 and 2022 studies. Both raise blood NAD+. Neither has a solid demonstrated clinical benefit, and no large trial compares them head to head.

Injection or capsule?

Every trial we have cited used oral precursors. Extrapolating their results to other routes of administration goes beyond what those studies measured. If someone presents an injectable while citing these trials, they are changing the question without telling you.

How much should I take?

Not a question this article can answer, and be wary of anyone who answers it without knowing you. What is known: the response varies between people by more than twofold, so a "standard" dose means little at the individual level.

Can I get NAD+ from food?

You do not take NAD+ directly from food, but you do take its raw material: niacin (vitamin B3), found in chicken, tuna, beef, peanuts, mushrooms and whole grains. The NIH fact sheet linked below has the amounts and recommendations.

What's the catch?

That the distance between "raises a biomarker" and "does you good" is larger than the marketing suggests — and that in this category almost all the commercial messaging lives in exactly that distance.

Why publish this if you sell health programs?

Because our slogan is not decoration. If we sold you an expectation the evidence does not support, we would win a sale and lose something worth more. We would rather tell you where the limit of what is known actually sits.

Do you offer care in Spanish?

Yes. All of our content and our care are available in Spanish and English.

Sources

• Martens CR, Denman BA, Mazzo MR, et al. Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD⁺ in healthy middle-aged and older adults. Nat Commun. 2018;9(1):1286. — DOI · via PubMed
• Conze D, Brenner C, Kruger CL. Safety and metabolism of long-term administration of NIAGEN (nicotinamide riboside chloride) in a randomized, double-blind, placebo-controlled clinical trial of healthy overweight adults. Sci Rep. 2019;9(1):9772. — DOI · via PubMed
• Liao B, Zhao Y, Wang D, et al. Nicotinamide mononucleotide supplementation enhances aerobic capacity in amateur runners: a randomized, double-blind study. J Int Soc Sports Nutr. 2021;18(1):54. — DOI · via PubMed
• Yi L, Maier AB, Tao R, et al. The efficacy and safety of β-nicotinamide mononucleotide (NMN) supplementation in healthy middle-aged adults: a randomized, multicenter, double-blind, placebo-controlled, parallel-group, dose-dependent clinical trial. Geroscience. 2023;45(1):29-43. — DOI · via PubMed
• Kuerec AH, Wang W, Yi L, et al. Towards personalized nicotinamide mononucleotide (NMN) supplementation: nicotinamide adenine dinucleotide (NAD) concentration. Mech Ageing Dev. 2024;218:111917. — DOI · via PubMed
• Martens CR, Decker KP, DeConne TM, et al. A phase-II randomized controlled pilot study of nicotinamide riboside supplementation in older adults with amnestic mild cognitive impairment. Alzheimers Dement. 2026;22(7):e71605. — DOI · via PubMed
• Niacin — Fact Sheet for Health Professionals. — NIH Office of Dietary Supplements
• Antioxidants: In Depth. — NIH National Center for Complementary and Integrative Health
• Compounding and the FDA: Questions and Answers. — U.S. Food and Drug Administration

The NAD+ elevation percentages and functional outcomes cited are averages from trials in specific populations and are not a forecast of your individual result. The 2026 study was conducted in people with amnestic mild cognitive impairment, not in healthy adults.

Your trust is worth more than a sale.

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This article is informational and is not medical advice. SCTS1 does not prescribe medications. All medical care, prescriptions and treatment plans are provided by licensed physicians through our partner platform, and compounded preparations are dispensed by licensed pharmacies. Eligibility is determined by a licensed provider through medical evaluation. NAD+ and its precursors are not FDA-approved to treat, cure or prevent any disease. The figures cited come from trials in specific populations and are averages, not a forecast for your case. Do not start, change or stop any medication or supplement on your own. Compounded medications contain the same class of active ingredient but are not FDA-approved finished pharmaceutical products. Individual results vary and are not guaranteed.