You are not imagining the change. The afternoon that flattens you. The workout that costs you two days now. The coffee that used to work and now just makes you jittery. You call it age, the way everyone does, as if that explains anything. It does not. One specific molecule is running out, and a clinic put eighty people on the thing that refills it.
Why Do You Feel More Tired as You Get Older?
Eighty people took a pill every morning for two months. At the end, their cells had stopped aging. The placebo group aged normally. Same clinic, same routines, different molecule. That molecule is NMN.
NAD+ is fuel for your cells. Every cell uses it to produce energy, repair damage, and keep things running. Your NAD+ levels drop by about half between ages 40 and 60. Less fuel means less energy. Your cells repair themselves more slowly. Your brain feels foggier. You recover from exercise slower. This decline in NAD+ is one of the key reasons aging feels the way it does.
Researchers at Harvard, Oxford, and Stanford have been studying ways to restore NAD+ levels.
What Is NMN and Why Is Everyone Talking About It?
You cannot just swallow NAD+ in a pill. Your body breaks it down during digestion before it can reach your cells. Instead, you take something called a "precursor," a building block that your body converts into NAD+ on its own.
The two main options are NMN and NR. Both are natural molecules found in tiny amounts in foods like broccoli and avocado, but nowhere near enough to make a difference. That is where supplements come in.
NMN is one step away from becoming NAD+ inside your cells. Dr. David Sinclair, a professor of genetics at Harvard, has been researching NMN for years and takes it himself every morning.
NR is a similar molecule, two steps away from NAD+. Dr. Charles Brenner, who first mapped NR's role in this process at the University of Iowa, advocates for this form instead. His team's 2016 study in Nature Communications (Trammell et al., PMID 27721479) was the first to show that an oral dose of NR raises NAD+ in people.
Both work. No definitive winner yet.
What Do the Clinical Trials Actually Show?
This is not just lab research on mice anymore. Real human trials have been completed:
NMN trial: A randomized, double-blind, placebo-controlled trial published in GeroScience in 2023 (PMID 36482258) gave 80 healthy middle-aged adults NMN or a placebo for 60 days, at doses of 300, 600, or 900 mg per day. NAD+ levels rose in every NMN group. Participants walked farther in a six-minute walking test and scored higher on a standard health questionnaire. The most notable result: the placebo group's measured biological age rose over the two months, while it stayed unchanged in all the NMN groups. The researchers identified 600 mg per day as the most effective dose.
NR trial: Human trials of NR have shown it raises NAD+ levels safely. The increases held throughout the studies, and no serious side effects were reported.
Both supplements raised NAD+ levels in humans. Both were safe. Both showed real benefits.
The Harvard Professor's Daily Routine
Dr. Sinclair has been open about what he personally takes: 1 gram of NMN every morning, plus 1 gram of resveratrol mixed into yogurt (the fat helps your body absorb it).
His reasoning is simple. NMN is the fuel. Resveratrol is the accelerator. Your body has built-in repair systems called sirtuins that need NAD+ to work. NMN gives them the fuel they need. Resveratrol tells them to work harder, similar to how exercise signals your body to get stronger.
NMN fills the tank. Resveratrol presses the gas pedal.
How Do You Choose a Third-Party Tested NMN?
The supplement industry has a quality problem. It is not well regulated, and independent testing has found that many products do not contain what their labels claim. Here is what to look for:
Third-party testing. This is the most important thing. Look for products verified by independent labs (NSF, USP, or similar). If a company does not test their products independently, move on.
Proper storage. Some forms of NMN break down in heat and moisture. Check if the product needs refrigeration and store it properly.
Dosage. Clinical trials typically used 250 to 500mg per day. Dr. Sinclair uses 1 gram, but there is no evidence that higher doses are necessarily better. Start with 250mg and see how you feel.
Timing. Take it in the morning. Your body's NAD+ levels naturally peak during daylight hours. Morning dosing aligns with this rhythm.
Sublingual options. Some NMN supplements dissolve under your tongue instead of being swallowed. This may help more of the NMN reach your bloodstream intact, though research on this delivery method is still ongoing.
The Honest Answer About NMN vs NR
Scientists have not reached a final verdict on which is better. Both raise NAD+ levels. Both have strong clinical evidence. Both are safe.
For a long time, researchers thought NMN was too large to enter cells directly. Then in 2019, a team reported a transporter protein (called SLC12A8) that appears to let NMN into cells through a direct pathway, especially in the gut (Grozio et al., Nature Metabolism, PMID 31131364). The finding is still debated, and other labs have questioned how large a role this pathway plays, so it is best read as an open question rather than a settled mechanism.
The bottom line: choose whichever form you can find from a trustworthy brand with proper testing. Consistency matters more than which precursor you pick. NAD+ restoration is a long-term strategy, not a quick fix.
What Else Supports NAD+ Levels?
Supplements are just one piece of the puzzle. Research from Harvard, the Salk Institute, and Stanford shows that these habits also help maintain your NAD+ levels naturally:
Eating within a time window (8 to 10 hours) activates the same repair pathways that NAD+ supports.
Regular exercise boosts NAD+ production and helps your cells use it more efficiently.
Good sleep is when your body does most of its repair work, and that work depends on NAD+.
Cold exposure activates cellular repair systems that work alongside NAD+.
Order a third-party tested NMN. 250mg. Morning. Empty stomach. Run it for 60 days. Measure your energy at day 1 and day 60. The data speaks for itself.
