Exclusive | Biohackers and stars like Hailey Bieber are obsessed with this longevity molecule — but is it the ‘holy grail of supplements’?

You know about DNA, but you may not have heard of NAD. You wouldn’t be alive without it.

NAD — short for nicotinamide adenine dinucleotide — is critical for energy production, DNA repair and cell survival. Scientists are investigating the potential for NAD+, the active form of NAD, to slow aging, boost brain health and increase disease resilience.

“It’s not new, but the research around the longevity, health span of it has really exploded,” functional medicine practitioner Will Cole, who advises Gwyneth Paltrow and other celebs, told The Post about NAD. “I think that’s why you’re hearing more and more of it.”

Because levels naturally decline with age, NAD+ tests, supplements and infusions have become big business.

Here’s the 411 on NAD as it sweeps Hollywood, finding fans in Jennifer Aniston and Hailey Bieber.

What’s NAD?

NAD is a coenzyme, which means that it helps other enzymes function.

“It is vital for activating enzymes called sirtuins and PARPs — classes of enzymes involved in DNA repair, longevity and inflammation,” Daniel Puleston, an assistant professor of oncological sciences at the Icahn School of Medicine at Mount Sinai, told The Post.

“For these reasons, NAD plays a fundamental role in humans and all other living organisms.”

It’s essential for the production of cellular energy in the form of ATP.

Longevity biomarker scientist Jin-Xiong She likens ATP to cellular gasoline.

ATP is primarily produced in mitochondria, the “powerhouses” of cells.

“If you don’t have enough NAD, your mitochondria don’t function efficiently,” She told the audience at a recent biohackers conference.

“You don’t produce enough ATP, but you produce more free radicals that can damage your DNA, damage your cell membrane — and that’s one of the major causes of disease.”

Where do we get NAD?

“Our two big sources of NAD are tryptophan, a protein product we can find in foods like red meat, dairy, poultry, nuts and beans, and some B vitamins,” Dr. Ayodele Oyeyemi, a Northwell Health geriatrician, told The Post. “We also recycle it in our bodies.”

Supplements are another route.

You can take NAD+, but the tablets are poorly absorbed by the body. Instead, the focus is on precursors like NMN (nicotinamide mononucleotide) and NR (nicotinamide riboside), which convert into NAD+ in the body.

NMN is produced from nicotinamide, a form of vitamin B₃. NMN can be found in small amounts in broccoli, edamame, avocados and cabbage.

NR is also a form of B₃ — it can be in milk, fermented beverages and yeast-containing foods.

“Oral supplementation of NAD precursors in humans, such as with nicotinamide riboside and nicotinamide mononucleotide, has shown to be safe over shorter periods (months) and successfully raise blood NAD levels,” Puleston said.

“However, results have been mixed, with many studies reporting no benefit for NAD treatment in areas such as metabolic performance, while others have reported modest improvements in muscle performance.”

How can we tell if we’re low on NAD+?

Research suggests that NAD+ levels can significantly decrease with age, but this process isn’t well understood.

Naturopathic doctor Sogol Ash said fatigue, neurological decline and brain fog are key symptoms of deficiency.

“We get an increase in that oxidative stress, those ugly cells, immune dysfunction, inflammaging — that’s like chronic low-grade inflammation that leads to disease,” Ash said at the biohackers conference.

Ash and other longevity enthusiasts recommend testing to figure out your NAD+ levels and experimenting with supplementation to improve those numbers.

Jin-Xiong She, for one, sells a $198 finger-prick test designed to “reveal your deficiency and provide actionable data to effectively enhance your NAD levels.”

Before you get out your credit card, Puleston and Oyeyemi cautioned that at-home NAD+ testing kits aren’t worth your time or money.

Puleston pointed out that there’s no universal consensus on what constitutes “high,” “adequate” or “low” NAD+ levels.

“And although levels decline in some tissues when comparing young versus old, we don’t quite yet understand if those decreases are meaningful or have a consequential impact on health,” he said.

How can we boost NAD+ levels?

Besides capsules, there are also NAD+ IVs, injections, nasal sprays and topical creams, but the research is limited there too.

“IV administration of NR and NMN has been shown to safely increase NAD levels in blood,” Puleston said. “There is a lack of trials assessing the capacity of IV NAD therapy to positively impact overall health, but a small study did report improvements in cognition and neurological function.”

Aniston, 56, and Bieber, 28, have endorsed NAD+ IV therapy, with Bieber declaring that she’s going to “NAD for the rest of my life, and I’m never gonna age.”

Ash — an adviser for Niagen Bioscience, which sells NAD+ products — is also a fan. She takes 1,000 milligrams of NR in the morning and does IV therapy with 1,000 mg of NR twice a month.

“NAD isn’t something that just builds up and stays in your body. You’re constantly using it. You’re constantly turning over mitochondria,” Ash said. “You’re constantly using energy, so you have to keep taking NR.”

Cole, the functional medicine practitioner, prefers oral supplementation to IVs. When he consistently consumes an NAD precursor, he “definitely can notice a difference in increased energy.”

Still, he suggests supporting NAD+ levels through weight training, better nutrition and inflammation reduction.

“There’s not going to be one magic pill where it’s like, ‘This is it. This is the holy grail of supplements,’ and it’s going to solve all your woes,” he said.