What does a NAD supplement do, and does it work in humans?
NAD supplements demonstrably raise NAD levels in your blood, but whether you actually benefit from that remains uncertain. If you want to try it, keep your expectations realistic and choose a dosage with the best available evidence.
NAD+ is a molecule present in every cell. It helps release energy from food and at the same time activates enzymes involved in DNA repair and slowing down ageing processes. As you get older, NAD+ levels in the body decline. This relationship is well documented in animal research; in humans it is plausible, but not yet proven, that this decline is the cause of health problems.
Whether a supplement can reverse that decline has been studied most extensively in humans for NR (nicotinamide riboside). It demonstrably can: taking 100 to 1000 mg of NR daily raises NAD+ levels in blood and skeletal muscle by 22% to 142%, depending on the dose. This is one of the most robust findings in the available human research. If you want to raise your NAD levels as a healthy adult, the evidence for NR or NMN (nicotinamide mononucleotide) is comparable; the practice card gives 300 to 600 mg NMN per day or 1000 mg NR per day as a starting point, for at least 8 to 12 weeks. However, higher blood levels say nothing yet about what that actually does for your health.
That last point is precisely the problem. A carefully designed study in overweight people taking 1000 mg NR per day found no effect on insulin sensitivity, mitochondrial function, fat in the liver or muscles, blood pressure, or inflammatory markers. The great promises from animal studies did not materialise here. A small study in older men found that inflammatory substances in the blood decreased, but mitochondrial function in the muscles did not improve. Even with more NAD+ in the muscles, those muscles did not perform better at the cellular level.
A small crossover study in healthy middle-aged and older adults found indications of lower blood pressure and reduced arterial stiffness after 500 mg NR per day for 6 weeks, but the researchers themselves stressed that larger follow-up studies are needed. Some studies are funded in part by ChromaDex, the largest NR manufacturer, and some of the authors are employed by or serve as advisors to that company. This applies to those specific studies, not to all research covered in this overview.
NR is well tolerated in studies lasting up to 8 weeks. No notable flushing (the red, itchy sensation that ordinary vitamin B3 sometimes causes), no rise in bad cholesterol, and no other remarkable side effects have been reported. Too little is known about use beyond 8 weeks in humans to make any statements about long-term safety.
This answer draws on four randomised studies in humans, supplemented by three reviews on the mechanism and biology of NAD+. The finding that supplements raise NAD levels is well supported; for health benefits, the evidence is thin and inconsistent. The researchers themselves note that larger studies are needed, and two studies originate from supplement manufacturer ChromaDex.
What are the effects if you take NAD every day?
Taking 600-900 mg of a NAD supplement per day raises your NAD levels and provides some benefit for endurance, but long-term safety has not yet been properly studied.
Are NAD+ supplements (NMN/NR) worth it?
NMN and NR demonstrably raise NAD+ in your blood and appear to be safe, but whether you will notice any benefit in muscle strength, heart function or memory has not yet been proven in humans. Note also: NR is authorised in the EU as a supplement; NMN is not (yet).
At what age does taking NAD+ supplements make sense?
There is no established age at which NAD+ supplementation becomes worthwhile. Studies focus on middle-aged and older adults, but a measurable functional benefit in humans has not yet been demonstrated.
Does NAD+ supplementation slow biological ageing?
NAD+ supplements raise your NAD+ levels in the blood, but whether that also means you age biologically more slowly has not been demonstrated in humans. The question is interesting, but firm conclusions are not yet available; keep an eye on future large-scale research if you are seriously considering this.
Which supplements or medications are best not combined with NAD+?
The combination of NAD+ supplements, particularly nicotinamide, with platinum-based chemotherapy is the most concrete reason for caution. For other interactions the indications are preliminary, but worth discussing if you use multiple substances.
Does a NAD+ infusion do something that an NMN pill does not?
No study directly compares a NAD+ infusion with an oral NMN pill, so an advantage of the infusion has not been demonstrated. Oral NMN demonstrably raises blood NAD+ levels, but whether you notice any health benefit from this remains unclear for now.