The theory outpaced the actual data, then marketing took over
For more than a decade, a molecule called NAD+ was elevated from laboratory curiosity to cultural phenomenon, carried aloft by celebrity endorsements and the deeply human wish to slow the passage of time. Now, a study published in Nature Metabolism has found that the foundational premise of this multimillion-dollar supplement market — that blood NAD+ levels fall as we age — does not hold up in humans. The story is less about a single molecule than about how hope, commerce, and incomplete science can fuse into something that resembles certainty long before the evidence warrants it.
- A Nature Metabolism study of more than 300 people across seven datasets found that blood NAD+ levels do not decline with age, directly undermining the core claim that has sustained a booming supplement industry.
- Celebrities from Gwyneth Paltrow to Kendall Jenner and influential voices like Andrew Huberman had already embedded NAD+ into mainstream wellness culture, creating a market whose momentum may outlast the science that challenged it.
- Some researchers argue the story is not over — NAD+ does appear to drop in specific tissues like muscle and brain — but even they concede the evidence is preliminary and a mouse study showed dramatic muscle NAD+ reductions caused no measurable harm.
- Scientists who study the field describe a pattern where early animal models were treated as human proof, the supplement industry filled the vacuum, and the distinction between hypothesis and established fact quietly dissolved.
- The lead researcher, who originally hoped to build a biomarker test to guide supplementation, now questions whether healthy people have any reason to take NAD+ at all, while calling for the industry to communicate with far greater honesty.
For years, NAD+ — a molecule central to cellular metabolism — became one of the world's most fashionable anti-aging supplements, stocked at major pharmacy chains and endorsed by figures ranging from Gwyneth Paltrow and Hailey Bieber to neuroscientist Andrew Huberman and biohacker Bryan Johnson. The pitch was elegant in its simplicity: NAD+ levels fall as you age, so replenishing them should help you age better. The human evidence was thin, but the market flourished regardless.
Now a study published in Nature Metabolism has challenged the premise at the heart of it all. Analyzing blood samples from more than 300 people across seven independent datasets, researchers found that blood NAD+ levels do not actually decline with age. A second, still-unpublished study reached the same conclusion. The lead researcher, Riekelt Houtkooper of Amsterdam University Medical Center, admitted his team had designed the study hoping to validate a biomarker test for supplementation — and was genuinely disappointed by what they found.
The theory itself originated in animal research roughly two decades ago, when boosting NAD+ extended lifespan in yeast, worms, and mice. The leap to humans was never properly verified — measuring blood NAD+ is technically difficult — but the idea traveled through academic reviews, conferences, podcasts, and social media until hypothesis had hardened into assumed fact. As Matt Kaeberlein of the University of Washington observed, the theory simply "outpaced the actual data," and once the supplement industry arrived, the demand for rigorous evidence largely evaporated.
Not everyone accepts the findings as the final word. Joseph Baur of the University of Pennsylvania notes that NAD+ does appear to decline in specific tissues — muscle and brain — and argues that tissue-level changes may be what matters most. But he acknowledges the research is still early, and a recent mouse study found that reducing muscle NAD+ by 85 percent produced no detectable harm to physical function. Even an executive at a major NAD+ supplement company conceded that influencer messaging had oversimplified the science.
Houtkooper has not ruled out therapeutic uses for NAD+ — he is now exploring whether it might benefit people with rare genetic metabolic disorders — but he is skeptical it belongs in the daily routines of healthy individuals. The larger question hanging over the field is whether new evidence can slow a market already built on enormous cultural momentum, or whether the distance between what scientists actually know and what consumers believe will simply continue to grow.
Gwyneth Paltrow swallowed it. So did Kendall Jenner and Hailey Bieber. The neuroscientist Andrew Huberman endorsed it. The biohacker Bryan Johnson made it part of his regimen. For years, NAD+—nicotinamide adenine dinucleotide, a molecule involved in cellular metabolism—became one of the most sought-after anti-aging supplements in the world, sold by trendy supplement companies and stocked on the shelves of Walgreens and Walmart. The pitch was simple: NAD+ levels drop as you age, so taking a supplement could help you age better. The evidence in humans was thin, but the market boomed anyway.
Now a new study has pulled at a thread that may unravel the whole foundation. Researchers analyzing blood samples from more than 300 people across seven different datasets found something unexpected: blood NAD+ levels do not actually decline with age. The study, published this month in Nature Metabolism, contradicts the central claim that has driven the supplement industry for years. A second study, still awaiting peer review, reached the same conclusion.
The theory itself is not new. About two decades ago, scientists studying yeast, worms, and mice discovered that boosting NAD+ could extend lifespan in those organisms. The idea migrated to humans, but there was a problem: measuring blood NAD+ levels is technically difficult, so no one could actually verify whether the decline happened in people. The theory took on a life of its own anyway. It appeared in review articles, was discussed at conferences, and eventually landed in podcasts and on social media, where it hardened into something that looked like fact. By the time it reached the supplement market, the distinction between hypothesis and evidence had largely disappeared.
Riekelt Houtkooper, a professor of translational metabolism at Amsterdam University Medical Center who led the new research, said his team initially designed the study hoping to develop a biomarker test that could help people decide whether to take NAD+ supplements. "We were very disappointed with the results," he said. The findings do not sit well with everyone. Joseph Baur, a physiology professor at the University of Pennsylvania, noted that while blood levels may not decline, other research has found that NAD+ does drop in specific tissues—muscle and brain among them. That tissue-level decline, he argued, might be what matters. But he acknowledged that research is still preliminary. A mouse study published last year showed that reducing NAD+ in muscle by as much as 85 percent did not appear to harm the animals' physical function.
The gap between what the science actually shows and what consumers hear has become a chasm. Matt Kaeberlein, an associate professor at the University of Washington who studies NAD+ but was not involved in the new research, put it plainly: the theory "outpaced the actual data." High-profile scientists have presented early-stage models as proven facts, he said, and once the supplement industry got involved, "the need for data evaporated, and it all became a marketing exercise." Andrew Shao, a senior vice president at Niagen Bioscience, which sells NAD+ supplements, acknowledged that "the message to consumers and the recommendations spread by influencers out there have probably been oversimplified too much." He suggested the industry needs to do better at explaining that any decline happens in tissues, not in blood.
Houtkooper has not abandoned the possibility that NAD+ could have therapeutic value, but he is skeptical it belongs in the medicine cabinets of healthy people. He is now investigating whether it might help those with rare genetic diseases affecting cellular metabolism. "There are still many possibilities in the NAD+ field," he said. "But I think in the last 15 years or so, it has been incredibly overhyped." The question now is whether the new evidence will slow a market that has already built enormous momentum, or whether the gap between what scientists know and what consumers believe will simply widen further.
Citas Notables
The theory outpaced the actual data. Once it entered the supplement space, the need for data evaporated, and it all became a marketing exercise.— Matt Kaeberlein, University of Washington researcher
We were very disappointed with the results. I don't believe there is any reason for normal, healthy people to take it as a supplement.— Riekelt Houtkooper, lead researcher, Amsterdam University Medical Center
La Conversación del Hearth Otra perspectiva de la historia
So the celebrities were taking something based on a theory that might not be true?
Not exactly. The theory—that NAD+ declines with age—came from solid animal research. But when it moved to humans, the evidence never really caught up. Blood tests are hard to do, so people just assumed it was happening.
And now someone finally did the blood tests?
Yes. They looked at over 300 people across seven different datasets. Blood NAD+ levels stayed stable across ages. That's the surprise.
Does that mean the supplements don't work at all?
Not necessarily. Some research shows NAD+ does decline in specific tissues like muscle and brain. But whether that decline is large enough to actually harm a healthy person—that's still unclear.
So why did the industry grow so fast if the evidence was so thin?
Because the theory sounded plausible, the animal studies were real, and once celebrities started talking about it, marketing took over from science. The industry didn't need proof anymore—it had influencers.
What should someone do if they're already taking it?
That's the honest answer: we don't know. The researchers aren't saying it's harmful. They're saying healthy people probably don't need it, and the reasons people were told to take it might not be what we thought.