These molecules become NAD+ over a series of chemical transformations. Here’s what you need to know about each one.
Key Takeaways:
- Our body synthesizes NAD+ from five different precursors which can be obtained through diet: Nicotinamide Riboside (NR), Nicotinamide Mononucleotide (NMN), Nicotinic Acid (NA), Nicotinamide (Nam), and Tryptophan (Trp).
- NR and NMN are the most efficient of the precursors. Numerous clinical studies have demonstrated that oral supplementation with NR or NMN increases NAD+ levels in humans.
- NR, NMN, NA, and Nam are forms of vitamin B3. Trp is the least efficient precursor and is an amino acid, not a vitamin B3.
Related Products:
Basis: contains NR and pterostilbene, which work together to support cellular aging and healthy DNA by increasing NAD+ levels and activating SIRT1.
Signal: contains NMN, honokiol, and viniferin. These ingredients work synergistically to support metabolic aging and mitochondrial function by increasing NAD+ and activating SIRT3.
NAD+ is a critical coenzyme in the body that’s involved in hundreds of cellular processes. The acronym stands for nicotinamide adenine dinucleotide, a coenzyme that plays a vital role in cellular metabolism by turning nutrients into cellular energy. It also works as a helper molecule with other proteins that regulate biological processes. The downside is that NAD+ levels decline with age.
But where do we get NAD+ from in the first place? Through our diet, from foods containing NAD+ precursors, which are the raw materials that become NAD+ through a series of chemical transformations. The body also uses and regenerates NAD+ via chemical reactions. There are many NAD+ precursors, but not all of them are as widely studied or bioavailable as others, so research and NAD+ supplements have largely focused on the five listed below. Here’s what you need to know about each one and how you can get more of them.
Nicotinamide Riboside (NR)
Nicotinamide riboside is a form of vitamin B3 often thought of as a highly efficient precursor, meaning it uses up the least amount of energy to become NAD+ when taken orally. This is because NR bypasses a step in the NAD+ biosynthetic pathway, which is also the route for nicotinamide (or Nam). NR is increasingly being used for NAD+ supplementation, as it’s known that NR can increase NAD+ levels (learn about our NR supplement Basis). In animal studies, this increase leads to concrete benefits like mitochondrial health, but to date, there is not yet evidence that these animal studies can be extrapolated to humans.
Nicotinic Acid (NA)
This is a form of vitamin B3 and is also known as niacin, a word sometimes used as an umbrella term for all vitamin B3s. Nicotinic acid was discovered by a chemist studying nicotine, and the name was changed to niacin in order to differentiate it from tobacco. NA is commonly known to cause flushing. Since the 1940s, NA has been used to fortify flour and rice all over the world because of its benefits. NA makes its way to NAD+ via the Preiss-Handler pathway, which also consolidates the chemically transformed tryptophan (an amino acid NAD+ precursor) to become NAD+.
Nicotinamide (Nam)
This is a form of vitamin B3 and is sometimes referred to as niacinamide (again, renamed to disassociate it from the tobacco family of nicotine). Nam goes through the same salvage pathway as NR but has to stop at the rate-limiting step that NR can bypass before it becomes NAD+. Nam is also involved in the salvaging part of the pathway. When NAD+-consuming enzymes, like sirtuins (a family of proteins that regulate cellular health) use NAD+, they split it into parts, using what they need and then sending the Nam back through the pathway to create more NAD+.
Nicotinamide Mononucleotide (NMN)
This NAD+ precursor toes the line of being a vitamin B3 depending on who you ask. It’s an intermediate compound between NR and NAD+, meaning NR has to become NMN before it becomes NAD+. NMN is the new kid on the block of NAD+ precursors and appears to have a unique transporter for entering cells. Human clinical studies are also confirming that dietary supplementation with NMN leads to elevated NAD+ levels (learn about our NMN supplement Signal). For a closer look at how NMN and NR compare, the two are best understood side by side.
Tryptophan (Trp)
This NAD+ precursor is most well known for being in turkey, so it’s often mistaken as a chemical that can make you tired — although it’s only earned this reputation from post-Thanksgiving-dinner exhaustion. It’s also sometimes thought of as a vitamin B3, though it’s actually an amino acid. Trp goes through the de novo biosynthesis pathway to become NAD+. Once it’s converted into other molecules, it merges with the Preiss-Handler pathway, the same pathway that NA takes to get to NAD+. While Trp does yield NAD+, it’s up to 60 times less efficient than other precursors.
Which NAD+ precursor is best?
No single precursor is best for everyone, but the list narrows fast. NR and NMN carry the most human research, and trials consistently show that oral NR or NMN raises blood NAD+ levels in adults, even as the downstream health effects of that increase are still being worked out. NA, Nam, and tryptophan still matter for understanding how NAD+ is made and recycled, but they are not where most of the human evidence sits.
NR is often described as the most efficient precursor because it enters NAD+ production through a dedicated route, skipping a rate-limiting step that other forms have to pass through. NMN sits just one step from NAD+ itself. Both are efficient on paper, and which of the two is better in people remains an open question.
Here is how the five compare on the details that actually distinguish them:
| Precursor | What it is | Route to NAD+ | Causes flushing? | Human evidence for raising NAD+ |
|---|---|---|---|---|
| NR (nicotinamide riboside) | Form of vitamin B3 | Salvage route; skips the rate-limiting step | No | Well studied in humans |
| NMN (nicotinamide mononucleotide) | B3-like intermediate | One step from NAD+ | No | Well studied in humans |
| NA (nicotinic acid / niacin) | Form of vitamin B3 | Preiss-Handler pathway | Yes | Converts to NAD+; high doses flush |
| Nam (nicotinamide) | Form of vitamin B3 | Salvage pathway | No | Converts via salvage; less direct than NR |
| Trp (tryptophan) | Amino acid (not vitamin B3) | De novo pathway | No | Dietary source only; ~60x less efficient |
For most readers comparing options, NR and NMN are the two precursors with real human data behind them. The rest of the choice comes down to formulation, format, and how a supplement fits your routine rather than the precursor label alone.
Can you just take NAD+ directly?
Taking NAD+ itself sounds like the obvious shortcut, but absorption gets in the way. NAD+ is a large molecule, and the body does not take it up whole.
When NAD+ from food reaches the gut, it is broken down into nicotinamide before it is absorbed. In other words, your body already treats dietary NAD+ as a source of precursors rather than as a finished coenzyme it can use as-is.
That is why supplements and food supply the building blocks instead of NAD+ itself, and why precursor research has centered on NR and NMN. The practical lever is the precursor, not the coenzyme.
Which foods are high in NAD+ precursors?
Most people get their NAD+ precursors from everyday food, mainly in the form of niacin. Animal proteins are the richest sources of preformed niacin: a three-ounce serving of chicken breast, turkey, salmon, tuna, or lean beef supplies a meaningful share of a day's niacin, and beef liver is higher still.
Plant foods contribute smaller amounts, mostly as nicotinic acid. Peanuts, brown rice, whole grains, legumes such as lentils, and seeds all add to the total. Many breads and cereals are fortified with niacin as well, which is part of why outright deficiency is rare across most of the world.
Protein foods do double duty. Beyond preformed niacin, they supply tryptophan, the amino acid the body can convert into NAD+ at a rate of roughly 60 milligrams of tryptophan to 1 milligram of niacin. Turkey is the famous example, though eggs and dairy contribute tryptophan too, even though they carry very little niacin on their own.
So a varied diet built around protein, whole grains, legumes, and nuts covers the precursor bases for most people. Supplements enter the picture when the goal is to raise NAD+ beyond what diet alone tends to deliver.
Is NAD+ the same as vitamin B3?
Not exactly. Vitamin B3, or niacin, is an umbrella term for a group of related compounds: nicotinic acid, nicotinamide, and derivatives such as nicotinamide riboside. NAD+ is the coenzyme your body builds from those B3 forms. B3 is the raw material, and NAD+ is the finished molecule the raw material becomes.
That distinction is why the precursors on this list are not interchangeable with NAD+ itself. NR, NA, and Nam are forms of vitamin B3. NMN sits at the edge of the category depending on who is defining it, and tryptophan is an amino acid rather than a B3 at all.
You can read more about the three forms of vitamin B3 and how each one feeds NAD+ production.
The two precursors that lead the field
Across all five precursors, two do most of the practical work: NR and NMN. Both are efficient, both are the focus of ongoing human research, and both reliably raise blood NAD+ in the studies done so far. The other three still matter for understanding how the body makes and recycles NAD+, but they are not where most of the evidence sits.
The other practical point is that NAD+ is built, not borrowed. Your body assembles it from precursors, whether those come from a varied diet rich in protein and whole grains or from a targeted supplement. Knowing which precursor you are getting, and from where, is the useful place to start.
Get Elysium news, subscriber-only product offers, and a monthly digest of new research in the field of aging. Sign up for our newsletter.
