Each morning for a week, ten young men braced themselves before slipping into tubs of frigid water — just 14 degrees Celsius, or 57 degrees Fahrenheit. For an hour at a time, they sat still in the cold, their skin prickling, muscles taut, breathing shallow. They weren’t athletes training for a polar plunge, nor were they following an influencer’s health craze. They were volunteers in a scientific experiment at the University of Ottawa, where researchers were investigating what cold really does to our cells.

The gist of the findings is that cold exposure makes cells more resilient.

According to the researchers led by Kelli King, a postdoctoral fellow, and Glen Kenny, a professor at the University of Ottawa’s School of Human Kinetics, cold exposure specifically boosts autophagy — the process by which cells clean out and recycle damaged components. This ancient cell mechanism is thought to be critical for maintaining healthy cells and preventing disease.

“This work shows that 7-day cold acclimation elicits improvements in cellular cold tolerance in young males through enhanced autophagic responses concomitant with reductions in apoptotic signaling,” the researchers wrote in their study published in Advanced Biology.

From Cell Death to Cellular Defense

Humans are bad at staying warm. Unlike Arctic foxes or polar bears, we lack fur, blubber, and natural insulation. So, when we plunge into cold water, it doesn’t take long before our core temperature starts to drop — and our cells start to panic.

Cold temperatures disrupt delicate cellular machinery. Proteins misfold. Membranes stiffen. Chemical reactions slow to a crawl. If the stress becomes too great, the cell activates its self-destruct protocol: apoptosis.

But the human body also has a survival mechanism — a process called autophagy, which literally means “self-eating.” In this mode, cells sweep up damaged proteins and organelles and recycle them, giving themselves a second chance.

When it functions properly, autophagy acts like a microscopic janitor, removing cellular debris before it can cause harm. When it fails, damaged proteins and organelles accumulate — something seen in diseases ranging from Alzheimer’s to cancer.

What the Ottawa researchers found was that cold acclimation appears to tip the balance in favor of autophagy.

7 Days in the Cold

At the start of the cold exposure regimen, participants’ blood cells showed signs of stress: elevated inflammatory markers, dysfunctional autophagy, and increased levels of cleaved caspase-3, an enzyme that activates apoptosis.

But by Day 7, the cellular signature had shifted. Damaged protein markers like p62 had declined. Levels of LC3-II, an indicator of active autophagy, had climbed. Apoptotic markers dropped. The cells were no longer flailing in response to the cold — they were adapting.

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

“Cold exposure might help prevent diseases and potentially even slow down aging at a cellular level,” King added. “It’s like a tune-up for your body’s microscopic machinery.”

To test whether these changes were more than fleeting, the researchers also exposed participants’ blood cells to simulated hypothermia in the lab. They cooled blood samples down to temperatures as low as 4°C — before and after the 7-day cold immersion protocol.

Before acclimation, the cells showed little capacity to resist cold stress. But after a week of training, those same cells showed increased autophagic activity, less evidence of apoptosis, and improved stability under hypothermic conditions.

What Does This Mean for Human Health?

The idea that we can train our cells to better withstand cold is both ancient and radical. Athletes, mountaineers, and traditional healers have long embraced the cold for its invigorating effects. Wim Hof, the Dutch “Iceman,” is famous for popularizing extreme cold exposure as a route to wellness. Now, scientists are beginning to uncover the cellular choreography behind those benefits.

This study, though small (just 10 young men), suggests that cold exposure can activate molecular pathways associated with longevity and disease prevention. Autophagy, in particular, has been linked to protection against neurodegenerative diseases, aging, and even cancer.

In many ways, this study is timely. It arrives at a time when cold plunges have surged in popularity on social media, promoted by wellness influencers and professional athletes alike. But until now, most claims about the benefits of cold exposure have been anecdotal, or loosely linked to broader research on stress adaptation.

Still, the researchers are cautious. The participants were all healthy young men. Whether these benefits extend to women, older adults, or people with chronic conditions remains unknown.

Cold water immersion is also not without risks, especially for people with heart conditions or underlying health problems. But the idea that short-term stress can bolster long-term resilience fits with a growing body of research into hormesis — the idea that what doesn’t kill you (in small doses) may make your biology stronger.

For now, the results offer a compelling biological explanation for why cold therapy might work — at least under the right conditions.