Cold plunges improve your health by literally changing your cells

In recent years, cold plunges have become a fixture on wellness feeds and gym schedules. People swear by them – claiming everything from mental clarity to faster recovery. But what does science say when you strip away the hype?

A team of researchers at the University of Ottawa has taken a closer look. Their work didn’t just explore how our bodies handle cold on the outside. It examined what happens on a much deeper level: inside your cells.

The results of the study could shape how we think about cold exposure and its place in everyday health.

Cold plunges change cells in one week

The Human and Environmental Physiology Research Unit conducted a tightly controlled experiment with ten healthy young men.

Over seven days, each participant immersed himself in 14°C (57.2°F) water for one hour per day. Blood samples were drawn before and after the cold-water sessions on days 1, 4, and 7.

The aim wasn’t to measure surface-level outcomes like muscle soreness. Instead, the team analyzed peripheral blood mononuclear cells to examine cellular stress, recovery, and resilience.

They focused on autophagy (the body’s way of cleaning out damaged components) and apoptosis (programmed cell death).

“Our findings indicate that repeated cold exposure significantly improves autophagic function, a critical cellular protective mechanism,” said Professor Kenny.

“This enhancement allows cells to better manage stress and could have important implications for health and longevity.”

Early cold plunges caused stress

On the first day, the researchers found clear signs of stress. Cells showed an increase in proteins like p62, which typically accumulate when autophagy is disrupted.

LC3-II, a marker of autophagic activity, did not increase. Apoptotic signaling also rose, with a marked spike in cleaved caspase-3, a protein that signals a cell is on its way to self-destruction.

This meant that initially, the cold exposure was overwhelming the cells. The natural repair systems weren’t strong enough to counteract the damage. But that would begin to change by day four.

Signals of cellular recovery

By the fourth day of immersion, early signs of adaptation emerged. LC3-II levels began to climb slightly, and p62 dropped – although still above baseline.

However, caspase-3 remained high, indicating the cells were still battling stress. The balance had not yet tipped in favor of full recovery.

“By the end of the acclimation, we noted a marked improvement in the participants’ cellular cold tolerance. This suggests that cold acclimation may help the body effectively cope with extreme environmental conditions,” explained King, the study’s first author.

Day seven marked a significant change. LC3-II rose substantially, showing robust autophagic activity. p62 dropped below baseline.

Caspase-3 levels returned to near normal. The cells had started to regulate themselves more efficiently, showing they had adapted.

Cellular learning confirmed

To take it further, the researchers tested the participants’ blood cells in cold conditions outside the body – before and after the week-long immersion routine.

Known as ex vivo testing, this allowed the team to simulate hypothermic states (temperatures as low as 4°C) without endangering the volunteers.

Before acclimation, these tests revealed poor autophagic responses and increased apoptosis across all cold conditions.

But after the seven-day program, LC3-II increased significantly at every temperature below 35°C. Apoptotic signals, particularly cleaved caspase-3, decreased, while p62 remained lower across the board.

These shifts showed that cells had become better at handling cold stress, even when removed from the body. It wasn’t just temporary resistance – it was programmed cellular behavior.

Cold plunges triggered stress proteins

While tracking autophagy and apoptosis, the researchers also looked at heat shock proteins – namely HSP70 and HSP90.

These proteins help stabilize other proteins during stress. Both increased during cold immersion but did not change significantly across the seven days.

This suggests that the cold exposure was enough to activate them, but the level of stimulus did not escalate throughout the week.

Instead, it’s possible the body tuned its internal systems to respond more efficiently without ramping up these proteins further.

“This work underscores the importance of acclimation protocols in enhancing human health, especially in contexts where individuals are exposed to extreme temperatures,” noted Professor Kenny.

Cooling curve and shivering clues

Besides cellular markers, physiological changes supported the idea of adaptation.

By day seven, participants had smaller increases in blood lactate levels – indicating less shivering. The body was becoming more efficient at conserving heat without relying on rapid muscle contractions.

Cooling rates slowed too. Participants took longer to reach the cutoff esophageal temperature of 35.5°C. While core temperature didn’t differ much across days, these smaller indicators confirmed the shift in cold tolerance.

Life and death inside a cell

Interestingly, at colder temperatures (33°C and below), both autophagic and apoptotic signals rose post-acclimation.

This dual response could mean cells were trying to survive using every tool available. When stress surpassed a certain threshold, even enhanced autophagy wasn’t enough to prevent some cells from progressing toward death.

This mirrors findings in animal models, where excessive autophagy can trigger cell death if damage is too severe.

The takeaway? Cold adaptation boosts protection, but it’s not a magic shield against extreme stress.

Cold plunges may slow cellular aging

“We were amazed to see how quickly the body adapted,” said King. “Cold exposure might help prevent diseases and potentially even slow down aging at a cellular level. It’s like a tune-up for your body’s microscopic machinery.”

While this research focused on healthy young males, it opens a door for broader inquiry.

Could older adults benefit from structured cold exposure? What about people with chronic illnesses that impair autophagic function?

These are next steps scientists are eager to explore.

Cold exposure as health practice

This study presents a strong case for integrating safe, structured cold exposure into wellness routines.

Seven days of one-hour immersion changed how cells handled stress, repaired themselves, and avoided damage. It’s one of the first studies to show these changes at a molecular level in humans.

More research will help define guidelines: how cold, how long, and how often. But one thing is clear – the body learns. And when exposed with care, cold might not be something to avoid, but something to use.

Whether you’re an athlete or just someone curious about longevity, this research suggests that the answer might be hiding in plain sight – or maybe, in a tub of ice water.

The study is published in the journal Advanced Biology.