This is 40-something.
Kim Kardashian, 45, has tried to cling to her youth by undergoing skin-tightening treatments, traveling to Korea for stem cell therapy and even getting injected with salmon sperm in her visage.
Biohacker Bryan Johnson, 48, has worked to stave off death with an extreme protocol that includes five sessions of hyperbaric oxygen therapy a week, shockwave therapy thrice weekly and an 18-hour fasting schedule.
Besides frustrating changes to their hormones, muscle mass and skin, quadragenarians like Kardashian and Johnson also have to worry about a drop in their nicotinamide adenine dinucleotide (NAD⁺) levels.
Found in all living cells, the molecule plays a key role in cellular energy production, mitochondrial function, DNA repair and metabolism.
“NAD⁺ levels naturally decline with age, most significantly in the 40s, [contributing to] chronic inflammation, poor sleep, metabolic disease and prolonged stress,” Dr. Pooja Gidwani, a double board-certified internal and obesity medicine physician based in LA, told The Post.
That’s why Kardashian and Johnson have turned to nicotinamide mononucleotide (NMN) oral supplements to boost their NAD⁺ levels.
Here’s how NMN works in the body — and why it’s often better than NAD⁺ supplementation.
What is NMN?
NMN is a form of vitamin B3 that’s absorbed rapidly in the gut and converted into NAD⁺ while inside cells.
By supporting NAD⁺ levels, NMN may improve mitochondrial energy production, insulin sensitivity, muscle function and vascular health.
“Clinically, any benefits tend to show up as improved energy regulation, exercise tolerance or metabolic markers rather than dramatic cosmetic or weight-loss effects,” Gidwani said.
How do you start NMN supplementation?
NAD⁺ levels can be measured with specialized blood tests.
An NMN dose often ranges from 250 to 500 milligrams, Gidwani said, perhaps even going up to 1,000 mg. How and when you take the supplement is important.
“NMN is typically taken in the morning, as increasing cellular energy later in the day may interfere with sleep for some individuals,” Gidwani explained.
“NMN appears to be most effective when used alongside foundational lifestyle factors, including adequate sleep, regular physical activity, sufficient protein intake and overall metabolic health optimization.”
It tends to be most useful for older adults or metabolically stressed people who are already making these lifestyle changes, Gidwani said.
She noted that the most meaningful benefits of NMN are generally gradual and cumulative, developing over weeks to months of consistent supplementation.
Are there any downsides to NMN supplements?
“Short-term human studies suggest NMN is generally well-tolerated, but long-term safety data are still limited,” Gidwani said.
“Reported side effects are usually mild and may include gastrointestinal discomfort, headaches or sleep disturbances, particularly at higher doses or when taken later in the day.”
One potential issue is that NMN products vary widely in purity, potency and stability, which is why third-party testing and reputable sourcing are key.
The Food and Drug Administration does not regulate supplements the same way it regulates prescription drugs.
And NMN is not for everyone.
It should be used cautiously or avoided altogether by people being treated for cancer and pregnant or breastfeeding women.
“Individuals with complex medical conditions or those on multiple medications should discuss NMN use with a physician before starting supplementation,” Gidwani said.
How does NMN compare to NAD⁺ supplementation?
“NMN, as a precursor, is smaller, more bioavailable and readily converted inside cells into NAD⁺, making it a more effective oral approach,” Gidwani noted.
NAD⁺, in contrast, is a large molecule that cannot directly penetrate cell membranes. That’s why it’s typically administered via IV infusion or injection to bypass the digestive system.
Patients often experience intense, immediate effects from an NAD⁺ IV, while NMN users may notice subtle changes within hours, such as improved mental clarity or energy, particularly if baseline NAD⁺ levels are low.
Still, taking an NMN capsule or powder is “far more practical” for long-term use, Gidwani said.
“NAD⁺ IV therapy is expensive, time-consuming and often associated with side effects such as nausea, flushing, chest tightness or anxiety during infusion,” she continued.
“From a cost, convenience and adherence perspective, NMN is generally a more accessible option.”
Before you stock up on NMN …
Gidwani emphasized that NMN “may help optimize cellular energy pathways in the right context,” but it’s “not a miracle anti-aging drug,” nor can it replace sleep, exercise, nutrition or medical care.
“The goal of NMN supplementation is not to ‘supercharge’ the system, but to support normal cellular processes that become less efficient over time,” she said.
