The FDA reversed itself on NMN while the human evidence stayed thin

Key takeaways

• In late September 2025, the FDA reversed its 2022 stance and said NMN may be sold as a supplement, a decision about when it was first sold, not about whether it works.
• GSK paid about $720 million for the resveratrol company Sirtris in 2008, then dropped its resveratrol drug in 2010, citing minimal benefit and a possible kidney risk.
• In a 12-month German trial of 100 older adults, a daily spermidine supplement did no better than a placebo on memory.
• Two urolithin A trials, both paid for by the company that makes it, missed their main goals but showed gains in muscle endurance or strength.
• A 2025 NIH study found that blood taurine doesn’t reliably fall with age, undercutting the main reason taurine is sold as an anti-aging pill.

In late 2022, the FDA told two NMN ingredient suppliers that NMN no longer counted as a dietary supplement ingredient¹. NMN, short for nicotinamide mononucleotide, is a molecule the body can turn into NAD+, which cells use to make energy.

The agency’s reason had nothing to do with safety or results. NMN had been studied as a drug before it was sold as a supplement, the FDA said, and federal law generally keeps such ingredients out of supplements¹.

The supplement industry fought back. In March 2023, the Natural Products Association, a trade group, and the Alliance for Natural Health USA asked the FDA to reverse course¹. That September, the agency said competing priorities kept it from deciding¹. In August 2024, the trade group sued¹.

A federal judge paused the case so the FDA could reconsider, and the agency held off on enforcement against NMN supplements in the meantime¹. In late September 2025, the FDA reversed itself, accepting evidence that NMN was sold as a supplement in the U.S. as early as 2017². In December, it sent letters to two NMN ingredient makers confirming the change¹.

Notice what the fight was about: which came first, the drug research or the supplement sales. It was never a ruling on whether NMN slows aging.

That gap between headlines and proof runs through the longevity aisle. Much of the excitement started in animals; the taurine results below, for example, came from mice and monkeys¹⁰. We walk through what happened when each ingredient was tested in people, and who paid for the tests.

NMN and NR: a legal win, and a rating that hasn’t changed

NMN and its cousin NR, nicotinamide riboside, are sold to raise NAD+ levels. Our article on longevity clinics reviewed their small human trials and rated them promising but early. Nothing in the FDA’s 2025 decision changes that rating.

What the decision changed was paperwork. The FDA’s December 2025 letters went to SyncoZymes and Inner Mongolia Kingdomway, two ingredient suppliers, about their filings for NMN as a new dietary ingredient¹.

The trade group’s president called the result an unequivocal victory and said the group would push Congress to change the law’s drug-first rule¹. Readers wary of drug-company power may welcome that. The episode also shows how an ingredient’s legal status can flip while the science behind it stays put.

Resveratrol: a $720 million bet that didn’t pay off

Resveratrol once had a powerful backer. In 2008, the drug company GlaxoSmithKline (GSK) bought Sirtris Pharmaceuticals, which was developing a resveratrol-based drug, in a deal valued at about $720 million³.

It didn’t go well. In May 2010, GSK suspended a trial of SRT501, its special resveratrol formula, in people with advanced multiple myeloma, a blood cancer, after several developed kidney failure³. That December, GSK ended work on SRT501, saying it might offer minimal benefit and could indirectly worsen a kidney problem common in those patients³.

The human evidence for ordinary resveratrol pills has stayed thin. A 2013 review of clinical trials in the journal Current Pharmaceutical Design concluded that randomized human trials had so far offered very limited confirmation of its benefits⁴. The reviewers also warned that the safety of long-term high doses was unresolved, especially for people taking medicines, and that drug interactions were possible⁴.

Spermidine: a careful trial found no memory benefit

Spermidine supplements are marketed for brain health and healthy aging. In 2022, researchers in Germany reported one of the more careful tests of the idea, called SmartAge, in JAMA Network Open⁵.

They enrolled 100 adults aged 60 to 90 who felt their memory was slipping⁵. Half took 0.9 mg of spermidine a day from a wheat germ extract, and half took a look-alike placebo, for 12 months. Neither the volunteers nor the researchers knew who got which⁵.

The result was clear. Spermidine did no better than placebo on the main memory test, and no secondary measure changed significantly either⁵. Side effects were similar in both groups⁵.

One caveat: the dose was small, raising the volunteers’ daily spermidine supply by only about 10%⁶. The authors suggested testing higher doses⁵.

Funding came mainly from the German government, but a company, The Longevity Labs, paid to help develop the spermidine-rich extract used in the trial⁵.

Urolithin A: real signals, all from its maker’s trials

Urolithin A is sold to support mitochondria, the tiny power plants inside cells. Two of its human trials point in an interesting direction, with one big asterisk.

In the first, published in JAMA Network Open in 2022, researchers in Seattle gave 66 adults aged 65 to 90 either 1,000 mg of urolithin A or a placebo daily for four months⁷. The main goals weren’t met. The urolithin A group walked about 61 meters farther in six minutes than at the start, but the placebo group improved by about 43 meters, a difference small enough to be chance⁷. Measures of muscle energy production didn’t differ either⁷.

Some secondary results favored urolithin A. Hand and leg muscles kept working longer before tiring, and several blood markers fell, including C-reactive protein, a sign of inflammation⁷. All the volunteers were white, and about three-quarters were women⁷.

The second trial, called ATLAS, was published in Cell Reports Medicine in 2022. It gave about 90 inactive, overweight adults aged 40 to 64 a placebo, 500 mg or 1,000 mg a day for four months⁹.

It missed its main goal, a measure of peak exercise power. Leg muscle strength did improve in both urolithin A groups, and the study’s summary put the strength gain at about 12%⁹. Grip strength didn’t change⁹.

This is the asterisk. Amazentis, the company that makes the ingredient, paid for the first trial, according to a summary by the longevity advocacy group Lifespan.io, which also noted that the authors reported numerous conflicts of interest⁸. Amazentis sponsored ATLAS too, and several authors were its employees or scientific advisers⁹.

That doesn’t make the data wrong. It does mean independent teams need to repeat them.

Taurine: the premise behind the hype didn’t hold up

In June 2023, a research team reported in the journal Science that taurine, an amino acid, extended life in mice¹⁰. Mice given daily taurine lived 10% to 12% longer at the median, and middle-aged monkeys given it showed better bone, metabolic and immune measures¹⁰.

Part of the case rested on a decline. The team reported that blood taurine fell by more than 80% over the human lifespan¹⁰.

Even then, the authors urged caution. A commentary published alongside the study noted that long-term human safety trials were lacking, and that the human version of the mouse doses would be very high¹⁰. The mice got 500 to 1,000 mg per kilogram of body weight a day¹⁰.

Two years later, a federal team put that premise to the test. Scientists at the National Institute on Aging, including Rafael de Cabo and Maria Emilia Fernandez, measured blood taurine in three groups of people, who together ranged from 20 to 100 years old, and in monkeys and mice. They published the results in Science in June 2025¹¹.

Taurine didn’t reliably drop. Levels often climbed or held steady with age¹¹. Normal variation in taurine levels was often bigger than any change linked to age, and ties between taurine and health shifted from one group or species to the next¹¹.

So a taurine decline can’t serve as a general marker of aging, the team concluded. The NIH release added that no solid clinical data show taurine supplements benefit people¹¹.

Alpha-ketoglutarate: an eight-year “reversal” with no comparison group

One human study of alpha-ketoglutarate, or AKG, shows how a study can work as marketing.

In 2021, the journal Aging published a study of 42 people who had bought Rejuvant, a calcium AKG product with vitamin A or D, from Ponce de Leon Health¹². After 4 to 10 months, a saliva test that reads 9 spots on DNA said their biological age had dropped by about 8 years on average¹².

There was no placebo group. The volunteers were customers who bought the product and the test on their own¹²¹³. The study used one small clock and measured no health outcomes¹². The authors listed most of these limits themselves and called for randomized trials¹².

The ties ran close. The testing lab had a service agreement with the company, and one author was a consultant and board member for it¹². The company’s press release still described the design as “randomized retrospective”¹³. A companion guide in this series explains how to read a biological-age result before trusting a change in it.

Vitamin D and telomeres: a small signal from a big trial

Telomeres are protective caps on the ends of chromosomes. They shorten each time a cell divides, a process linked to aging¹⁵. In 2025, NIH-supported researchers checked them in 1,054 adults from VITAL, a five-year trial of about 26,000 people¹⁴¹⁵. Women were 55 or older and men 50 or older¹⁴.

People who took 2,000 IU of vitamin D3 a day lost about 140 fewer base pairs, the building blocks of DNA, over four years than people on placebo¹⁴. Telomeres started out at about 8,700 base pairs on average¹⁵. By our arithmetic, the difference was under 2% of their length.

The result was statistically significant, but only just: the low end of the likely range was 7 base pairs¹⁴. The National Heart, Lung, and Blood Institute, which funded the work, framed vitamin D as a possible anti-aging strategy only if the findings can be replicated¹⁵. Marine omega-3s, 1 gram a day, had no effect on telomeres¹⁴.

Related topics are covered elsewhere. Our article on anti-aging claims describes a Swiss trial in which omega-3 slightly slowed epigenetic clocks, and our fish oil article covers what omega-3 pills do and don’t do. A companion article on senescent cells covers fisetin and quercetin, and metformin is a prescription drug, discussed in our article on anti-aging claims.

The longevity aisle scorecard

This scorecard is our own, built from the sources cited.

Ingredient	Best human evidence	Who paid	Safety notes	Rating
NMN and NR	Small trials; see our longevity-clinics article	Varies by trial	2025 FDA decision was about legal status, not benefit12	Promising but early
Resveratrol	Little confirmed benefit in randomized trials as of a 2013 review4	A drug company’s program ended in 20103	High-dose safety unresolved; possible drug interactions4	Not enough evidence
Spermidine	One 12-month trial of 100 adults: no memory benefit at a low dose56	Mostly German government; a company funded the extract5	Side effects similar to placebo5	Not enough evidence; its best trial found no memory benefit
Urolithin A	Two 4-month trials; main goals missed, some muscle gains79	Amazentis, the maker89	Side effects similar to placebo7	Promising but early
Taurine	Longer life in mice; no human aging trials1011	2023 funders not listed in our sources; 2025 study run by NIA11	Mouse doses would be very high for people10	Not enough evidence in people
AKG (Rejuvant)	42 customers, no comparison group12	Company customer data; tester tied to seller12	No health outcomes measured12	Not enough evidence
Vitamin D for telomeres	About 140 fewer base pairs lost over 4 years14	NIH15	Counts toward your daily vitamin D total	Promising but early

Seven questions before you buy

1. What did the best human trial measure? A lab marker isn’t the same as feeling, moving or living better.
2. Did the trial meet its main goal? Both urolithin A trials missed theirs⁷⁹.
3. Who paid, and who made the product? Look for the funding line in the study itself⁸⁹.
4. Is the label dose the tested dose? The spermidine trial used 0.9 mg a day⁵; urolithin A trials used 500 to 1,000 mg⁷⁹.
5. Was there a placebo group? The AKG study had none¹².
6. Has an independent lab checked the label? Our article on supplement seals explains what each seal tests.
7. Does it clash with my medicines? Ask a pharmacist, especially about high-dose resveratrol⁴.

Skepticism that applies to every seller

Many natural-health readers distrust drug companies, often for good reason. The longevity aisle deserves the same scrutiny. Here, the trial sponsor is often the company selling the capsule⁸⁹¹².

That skepticism cuts both ways. Spermidine’s null trial was mostly publicly funded and well designed⁵. Urolithin A’s company-funded trials still produced signals worth testing independently⁷⁹. Judging the evidence, not the label or the sponsor alone, is the self-reliant move.

Talk with a clinician or pharmacist before you start if any of these apply:

• You take prescription medicines. Reviewers flagged possible drug interactions with high-dose resveratrol⁴.
• You’re being treated for cancer. GSK’s resveratrol trial in people with multiple myeloma was suspended after several developed kidney failure³.
• You plan to take large amounts of taurine. Long-term human safety trials are lacking¹⁰.

If you take several products, our article on supplement stacks shows how to add up doses, including vitamin D, against official upper limits.

Questions readers ask

The bottom line

Products in the longevity aisle come with good stories. In people, the record is thin: a null spermidine trial, company-funded urolithin A trials that missed their main goals, a taurine theory that didn’t hold, an AKG study with no comparison group and a vitamin D signal that needs repeating.

None of these has been shown to extend human life or healthspan. If you want to try one, treat it as an experiment: check who paid for the research, match the dose, ask a pharmacist about your medicines, and keep putting your first dollars and hours into the habits with stronger evidence.

Related reading

• How to sort longevity clinics that mix proven care with pricey experiments
• How to decode “reverse your age” ads that outrun the science
• Supplement Seals Test Different Things. Know Which One You’re Trusting
• A stack of safe supplements can add up to an unsafe dose
• Three questions to ask before you pay for a supplement

Sources

1. NutraIngredients. “FDA reinstates NDI status of NMN with new letters to ingredient players.” NutraIngredients, December 9, 2025. nutraingredients.com
2. Natural Products Association (supplement industry trade group). “Amid Pressure from NPA, FDA Declares NMN Lawful in Dietary Supplements.” NPA news release, September 29, 2025. npanational.org
3. Carroll J. “Weak efficacy, renal risks force GSK to dump a resveratrol program.” Fierce Biotech, December 1, 2010. fiercebiotech.com
4. Tomé-Carneiro J, Larrosa M, González-Sarrías A, Tomás-Barberán FA, García-Conesa MT, Espín JC. “Resveratrol and Clinical Trials: The Crossroad from In Vitro Studies to Human Evidence.” Current Pharmaceutical Design, 2013;19(34):6064–6093 (abstract via U.S. EPA HERO database). hero.epa.gov
5. Schwarz C, Benson GS, Horn N, et al. “Effects of spermidine supplementation on cognition and biomarkers in older adults with subjective cognitive decline: a randomized clinical trial.” JAMA Network Open, 2022;5(5):e2213875 (Max Delbrück Center repository record). edoc.mdc-berlin.de
6. Healio. “No improvement in memory biomarkers with spermidine supplement compared with placebo.” Healio Neurology, May 26, 2022. healio.com
7. Liu S, D’Amico D, Shankland E, et al. “Effect of Urolithin A Supplementation on Muscle Endurance and Mitochondrial Health in Older Adults: A Randomized Clinical Trial.” JAMA Network Open, 2022;5(1):e2144279 (EPFL Infoscience record). infoscience.epfl.ch
8. Lifespan.io (Lifespan Extension Advocacy Foundation). “Urolithin A Affects Muscle and Mitochondria in Older Adults.” Lifespan.io News, 2022. lifespan.io
9. Lifespan.io (Lifespan Extension Advocacy Foundation). “Urolithin A Improves Muscle Strength in Middle-Aged Adults” (on Singh A, et al., Cell Reports Medicine, 2022, ATLAS trial). Lifespan.io News, 2022. lifespan.io
10. GEN (Genetic Engineering & Biotechnology News). “Lifespan in Mice and Monkeys Improved by Reversing Taurine Deficiency” (on Singh P, et al., Science, 2023). GEN, June 2023. genengnews.com
11. National Institutes of Health. “NIH researchers conclude that taurine is unlikely to be a good aging biomarker” (on Fernandez ME, de Cabo R, et al., Science, 2025). NIH news release, June 5, 2025. nih.gov
12. Demidenko O, Barardo D, Budovskii V, et al. “Rejuvant, a potential life-extending compound formulation with alpha-ketoglutarate and vitamins, conferred an average 8 year reduction in biological aging, after an average of 7 months of use, in the TruAge DNA methylation test.” Aging, 2021;13(22):24485–24499. pubmed.ncbi.nlm.nih.gov
13. Ponce de Leon Health. “Study Shows Rejuvant Decreases Biological Age By Eight Years in Seven Months.” Company press release via GlobeNewswire, republished by BioSpace, November 30, 2021 (cited to show the company’s claim). biospace.com
14. Zhu H, Manson JE, Cook NR, et al. “Vitamin D3 and marine ω-3 fatty acids supplementation and leukocyte telomere length: 4-year findings from the VITamin D and OmegA-3 TriaL (VITAL) randomized controlled trial.” American Journal of Clinical Nutrition, 2025;122(1):39–47 (abstract via Food and Behaviour Research). pubmed.ncbi.nlm.nih.gov
15. National Heart, Lung, and Blood Institute. “Vitamin D supplements may slow cellular aging.” NHLBI in the Press, June 6, 2025. nhlbi.nih.gov