Can adults grow new brain cells? What the debate shows, and what it doesn't

For most of the twentieth century the rule was simple: you are born with all the brain cells you will ever have. Then came evidence that mice, rats and some monkeys keep making new neurons in the hippocampus, a region central to memory. Whether people do too has been one of neuroscience's longest fights, and in the past year it got new answers. It also got a new set of supplement ads.

Why scientists argued about it for decades

In 1998, a postmortem study reported new neurons in the human hippocampus. In 2013, carbon-14 dating estimated that about 700 new neurons are added to each hippocampus per day, a turnover of roughly 1.75% a year within a renewing third of its neurons. Then in 2018, Nature published a study by Shawn Sorrells and colleagues that found no young neurons in 17 adult control brains and 12 epilepsy samples from people aged 18 to 77, and concluded that neurogenesis does not continue, or is extremely rare, in adults. The same year, another team found thousands of immature neurons in hippocampi from people aged 14 to 79, and in 2019 a third group found them into the ninth decade, in smaller numbers in Alzheimer's. Everyone was working with postmortem or surgical tissue, and by 2021 Sorrells was writing that settling it would require someone to identify and visualize dividing neuronal precursors.

What the newest studies found

In July 2025, a team from Karolinska Institute and Chalmers led by Jonas Frisen reported in Science that it had seen those precursors: proliferating neural progenitor cells in the adult human dentate gyrus, the hippocampal region where new neurons form. The result varied enormously between people. Some adults had many progenitor cells and others hardly any, according to Karolinska's release. Marta Paterlini, a co-lead author, said the work puts the debate to rest. Not everyone agrees. Shawn Sorrells, whose 2018 paper found no such cells, told Popular Science that the likelier explanation is that they are rare or absent in most people.

In February 2026, Nature published the first large look at whether this changes with brain health. Researchers analyzed 355,997 cell nuclei from 38 brains: young adults, healthy older adults, people with preclinical and full Alzheimer's disease, and so-called SuperAgers, older adults with unusually sharp memories. SuperAgers had more immature neurons than people with Alzheimer's. A university press release said they made at least twice as many new neurons as their peers, but the paper is more careful. Only the comparison with Alzheimer's brains reached significance, the roughly twofold difference against other groups was not significant, and the authors wrote that inter-sample variability and low sample number compromised their analysis. The abstract says the cognitive relevance of these cells remains unknown. Perminder Sachdev of the University of New South Wales called the findings a promising lead that needs replication.

Animals are not people

Most of what is said about boosting neurogenesis comes from animals. New hippocampal neurons have been seen in rodents and some other primates since the 1960s, and running roughly doubled the number of surviving newborn cells in mice. In people, nobody has measured neurogenesis in a living brain. The best human exercise trial, 120 older adults in PNAS, found that aerobic training raised the volume of the anterior hippocampus by about 2% and improved spatial memory, but volume on a scan is not new neurons. Blood levels of BDNF, short for brain-derived neurotrophic factor, rise with exercise in a meta-analysis of 29 studies, driven by aerobic exercise rather than resistance training. That is a blood marker, not a count of new cells.

The supplement problem

Supplements are the weakest link. BDNF itself crosses the blood-brain barrier poorly, which researchers say limits its clinical use. Meta-analyses show blood BDNF rising with curcumin, omega-3 and zinc, but not with probiotics across 11 trials, and none of them measured neurogenesis. The NIH's National Center for Complementary and Integrative Health says direct evidence that dietary supplements can prevent Alzheimer's disease or other dementias is lacking. Lion's mane, often sold on a nerve-growth pitch, has mostly small trials, which we covered in our look at lion's mane for focus and memory.

What to do about it

You can't measure or steer this at home, so choose habits on the evidence for brain health, not for neurogenesis. In US POINTER, a JAMA trial of 2,111 adults aged 60 to 79, a structured lifestyle program edged out a self-guided one on cognition by 0.029 standard deviations a year. That is modest, and it says nothing about new neurons. Skip products that promise to grow brain cells, and see a doctor if memory is slipping.

Our take

Adults probably do make new neurons in the hippocampus, and the evidence is better than it has ever been. It is still small, variable and postmortem, nobody knows whether it helps memory, and no supplement has been shown to raise it. Treat "grow new brain cells" on a label as marketing, and treat exercise and a healthy lifestyle as the boring, better-supported bet.

This is general information, not medical advice. Talk to a clinician before changing anything, especially if you are pregnant, nursing, or managing a condition.