What Is NAD+? Why Levels Fall With Age and What Supports Them

You've probably seen "NAD+" on supplement bottles, in podcasts and in headlines about aging. But what is it, actually? In plain terms, NAD+ is a helper molecule that sits inside nearly every cell in your body and helps turn food into usable energy. It's not a vitamin, it's not a hormone, and it isn't something you need to buy to have. Your body makes it every day. This guide explains what NAD+ does, where it comes from, why researchers think levels drift down with age, what's still unknown, and where oral supplements fit in.

Key Takeaways

• NAD+ (nicotinamide adenine dinucleotide) is a coenzyme found in every cell. It takes part in energy metabolism and works alongside enzymes such as sirtuins.
• Your body builds NAD+ from vitamin B3 forms and the amino acid tryptophan, so food already supplies the raw materials.
• Research in animals and people suggests NAD+ levels tend to fall with age, but how much that matters, and what to do about it, is still being studied.
• Oral NAD+ supplements are almost always precursors, like nicotinamide riboside (NR) or NMN. OPA NAD+ is an NR-based precursor formula, not NAD+ itself.
• Sleep, movement and how you eat shape your cells' energy systems more reliably than any single capsule.

What NAD+ is, in plain English

Think of NAD+ as a shuttle. Your cells constantly move small charged particles called electrons from one chemical reaction to another, and NAD+ is one of the main carriers. A 2021 review in Nature Reviews Molecular Cell Biology describes it as a coenzyme for redox reactions, which is why it's central to energy metabolism. When NAD+ picks up electrons, it becomes NADH. When it drops them off, it goes back to NAD+. That back-and-forth happens constantly.

The same review points out that NAD+ has a second job. A group of enzymes, including sirtuins, CD38 and PARPs, use NAD+ as a required ingredient, and they're involved in things like DNA maintenance, chromatin remodeling and immune cell function. Those enzymes literally consume NAD+ as they work, which is part of why researchers care about how much is available.

NAD+ vs NADH: what's the plus about?

The "+" and the "H" tell you which state the molecule is in. NAD+ is the form that's ready to pick up electrons. NADH is the form that's carrying them. Cells need both, and what matters for energy metabolism is the balance between the two. When you see a product that says NADH, it's a different form from NAD+, and the research on it is separate. This guide, and the precursors we mention, are about the NAD+ side of the pair.

Three myths worth clearing up

• "Taking NAD+ in a capsule puts NAD+ in your cells." Not as far as the human studies show. The oral studies we've read test precursors, and they measure NAD+-related compounds in blood or muscle afterward.
• "Falling NAD+ means you're deficient." A drift in tissue levels over decades isn't the same as a vitamin deficiency. The ODS says most people in the U.S. get enough niacin from food.
• "More is always better." No trial we've seen shows that. Studies have used set doses for set periods, and the long-term picture is still being filled in.

Where your body gets NAD+

You don't absorb NAD+ from a meal. Your cells make it, and they have several routes to do that.

• From niacin (vitamin B3). According to the NIH Office of Dietary Supplements, niacin helps turn the food you eat into energy, and it's found in poultry, beef, pork, fish, some nuts, legumes and grains, plus enriched and fortified foods like many breads and cereals.
• From tryptophan. Your liver can convert this amino acid, found in protein foods, into niacin. The ODS notes that this conversion needs iron, riboflavin and vitamin B6.
• By recycling. Cells also reuse the pieces that are left over after NAD+ gets used up. Precursors like nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) feed into this recycling route.

The ODS also says most people in the U.S. get enough niacin from food. So when you hear "NAD+ is falling," that isn't the same as "you're deficient in vitamin B3." It's a more subtle research question about levels inside specific tissues.

Why researchers think NAD+ levels fall with age

The Buck Institute review we mentioned says aging is accompanied by a gradual decline in tissue and cellular NAD+ levels in multiple model organisms, including rodents and humans.

We want to be careful here. The same authors say plainly that much remains to be learned about how NAD+ levels are regulated, how to restore them effectively, whether doing so is safe, and whether it would help people as they age. In other words, "levels go down" is well supported as an observation, but "boosting them improves how people age" is still an open question. We'd rather tell you that than sell you a story.

What oral supplements can and can't do

This is where labels get confusing. Most products with "NAD+" in the name don't contain NAD+ as the active ingredient. They contain a precursor, which is a building block the body can use to make NAD+.

• NR (nicotinamide riboside) is a form of vitamin B3. In human trials, it has raised NAD+-related measures in blood and muscle. For example, a 6-week crossover trial in middle-aged and older adults found NR was well tolerated and raised NAD+ levels (Martens et al., 2018).
• NMN (nicotinamide mononucleotide) is another precursor. In a trial of healthy older men taking 250 mg a day, blood NAD+ went up (Igarashi et al., 2022).

Raising a lab measurement is one thing, and noticing a difference in how you feel or function is another. Across the trials we've read, the first has been shown fairly consistently, while the second has been mixed or small. We go through those trials one by one in our guide to NAD+ vs NMN vs NR, including doses, what was measured and where the FDA stands on NMN.

Where OPA NAD+ fits

Here's the plain version of what's in our bottle. OPA NAD+ is a nicotinamide riboside formula. Two capsules a day give you 500 mg of nicotinamide riboside chloride, 150 mg of trans-resveratrol, 50 mg of quercetin and 10 mg of galactomannans. It's an NR-based NAD+ precursor formula, which means it is not NAD+ itself, and it's designed for antioxidant support as part of a daily routine.* We'd also point out that several NR trials used 1,000 mg a day, which is double what's in a serving of ours, so we don't suggest it duplicates a study protocol.

Sirtuins and where resveratrol comes in

You'll often see NAD+ discussed next to resveratrol, so here's the connection. Sirtuins are NAD+-dependent enzymes. In a well-known 2003 paper in Nature, researchers reported that resveratrol, a polyphenol found in red wine, stimulated a sirtuin in lab experiments and extended the lifespan of yeast. That paper helped spark decades of interest.

It's also fair to say the story got more complicated. A 2010 study in the Journal of Biological Chemistry reported that resveratrol did not directly activate SIRT1 when tested with native substrates, which raised questions about how the earlier results were measured. Researchers still debate how resveratrol works in cells and what it does in people. We'll cover that debate in a future guide. For now, the point is that sirtuins need NAD+ to work, and resveratrol is one of the compounds that's been studied alongside them. That's why we pair the two in OPA NAD+, and why we also offer OPA Resveratrol 600 mg on its own.*

Everyday habits that shape your cells' energy systems

Your NAD+ supply doesn't live in a bottle. It's tied to how your cells handle energy, and that's influenced by routine habits.

• Movement. Exercise puts steady demand on your cells' energy machinery. See our guide to the best exercise to increase mitochondria.
• Food. Overall diet quality and how many calories you eat are active research areas. We've explained them in caloric restriction and longevity and diet and longevity.
• Sleep. Good sleep supports recovery in general. Our post on magnesium and sleep quality covers the basics.

Who should check with a clinician first

If you're pregnant or nursing, under 18, taking medicine, or managing a health condition, talk to your doctor or pharmacist before starting any NR or NMN product. Bring the bottle so they can see the full ingredient list. If you notice anything that worries you after starting a supplement, stop and get advice.

FAQ

What does NAD+ do in the body?

It's a coenzyme that helps cells turn food into energy, and it's also a required ingredient for enzymes such as sirtuins and PARPs. It exists in every cell.

Is NAD+ just vitamin B12?

No. NAD+ is a different molecule. It's built from forms of vitamin B3 (niacin), and from the amino acid tryptophan. B12 isn't part of it.

Does NAD+ cause weight gain?

We're not aware of evidence that it does. NAD+ is something your body already makes. Studies of the precursor NR in people have reported small or no changes in body composition, and those studies were small. If you're concerned, check in with your doctor.

Can I get NAD+ from food?

Not NAD+ directly. Foods supply niacin and tryptophan, and your cells build NAD+ from those. Poultry, beef, pork, fish, some nuts, legumes and grains are among the foods the ODS lists as sources of niacin.

Is OPA NAD+ actually NAD+?

No. It's a nicotinamide riboside (NR) formula, which is a precursor to NAD+. Each two-capsule serving has 500 mg of nicotinamide riboside chloride plus trans-resveratrol and quercetin.

Are NAD+ injections or IV drips the same thing as capsules?

No, and this guide is only about oral precursor supplements. Injections and infusions are medical services, and we don't make recommendations about them. If you're considering one, talk to a licensed clinician.

Sources

• Covarrubias AJ, Perrone R, Grozio A, Verdin E. NAD+ metabolism and its roles in cellular processes during ageing. Nat Rev Mol Cell Biol. 2021.
• NIH Office of Dietary Supplements. Niacin: Fact Sheet for Consumers.
• Martens CR, et al. Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adults. Nat Commun. 2018.
• Igarashi M, et al. Chronic nicotinamide mononucleotide supplementation elevates blood NAD+ levels and alters muscle function in healthy older men. npj Aging. 2022.
• Howitz KT, et al. Small molecule activators of sirtuins extend Saccharomyces cerevisiae lifespan. Nature. 2003.
• Pacholec M, et al. SRT1720, SRT2183, SRT1460, and resveratrol are not direct activators of SIRT1. J Biol Chem. 2010.

*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 education and isn't medical advice.