In recent years, cold plunges have become a fixture for wellness feeds and gym schedules. People swear to them – they insist on everything from mental clarity to faster recovery. But what does science say when you get rid of the hype?
Researchers team of University of Ottawa I look closely. Their work was more than just exploring how our bodies deal with the coldness outside. It looked at what happens on a deeper level: inside your cells.
The results of this study can shape how we think about cold exposure and its place in daily health.
Cold plunge changes cells in one week
Human and Environmental Physiology Research Unit A strictly controlled experiment was conducted on 10 healthy young men.
Over the course of 7 days, each participant was soaked in 14°C (57.2°F) water for 1 hour per day. Blood samples were drawn before and after the cold water session on days 1, 4, and 7.
The aim was not to measure surface level results, such as muscle pain. Instead, the team analyzed peripheral blood mononuclear cells to determine the stress, recovery, and resilience of the cells.
They focused on autophagy (the body’s method of cleaning damaged components) and apoptosis (programmed cell death).
“Our findings show that repeated cold exposure significantly improves autophagy function, a key cytoprotective mechanism,” Professor Kenny said.
“This strengthening allows cells to better manage stress and may have important implications for health and longevity.”
Early cold plunge caused stress
On the first day, researchers discovered clear signs of stress. Cells showed an increase in proteins such as p62. This usually accumulates when autophagy is destroyed.
The marker of autophagy activity, LC3-II, was not increased. Apoptotic signaling is also elevated, with a prominent spike in the cleaved caspase-3, the protein that signals the cells, leading to self-destruction.
This initially meant that cold exposure overwhelmed the cells. The natural repair system was not strong enough to counter damage. But that starts to change by the fourth day.
Signals of cell recovery
By the fourth day of immersion, early signs of adaptation appeared. Although LC3-II levels begin to rise slightly, although P62 is still above baseline.
However, caspase-3 remains high, indicating that the cells are still fighting stress. The balance was still not leaning in favor of a full recovery.
“By the end of adaptation, we focused on significant improvements in participants’ cell cold tolerance, suggesting that cold adaptation may help the body effectively deal with extreme environmental conditions,” explained King, the first author of the study.
Day 7 showed a major change. The LC3-II was significantly increased and showed robust autophagy activity. The P62 dropped under the baseline.
Caspase-3 levels have returned to normal. Cells began to regulate themselves more efficiently, indicating that they were adapting.
Cell learning has been confirmed
To further that, researchers tested participants’ blood cells in cold conditions outside the body before and after a week-long soaking routine.
Known as ex vivo testing, the team was able to simulate hypothermia (as low as 4°C) without putting volunteers at risk.
Before adaptation, these tests revealed poor autophagy responses and increased apoptosis in all cold conditions.
However, after a 7-day programme, the LC3-II was significantly increased at all temperatures below 35°C. Apoptotic signals, particularly cleaved caspase-3, were reduced, but P62 remained low throughout the board.
These shifts showed that cells were excellent at handling cold stress, even when removed from the body. It wasn’t just temporary resistance – it was the behavior of the programmed cells.
Cold plunge triggered stress protein
During the tracking of autophagy and apoptosis, researchers also looked at heat shock proteins, namely HSP70 and HSP90.
These proteins help stabilize other proteins during stress. Both increased during the cold soak, but not significantly changed over 7 days.
This suggests that cold exposure is sufficient to activate them, but the level of stimulation did not escalate throughout the week.
Instead, they may have tailored their internal systems to make their bodies respond more efficiently without increasing these proteins.
“This study highlights the importance of adaptation protocols in enhancing human health, especially in contexts where individuals are exposed to extreme temperatures,” Professor Kenny said.
Cooling curves and trembling cues
In addition to cellular markers, physiological changes supported the concept of adaptation.
By day 7, participants showed a smaller increase in blood lactic acid levels and less tremors. Without relying on rapid muscle contractions, the body was becoming more efficient at saving heat.
The cooling rate has also slowed down. Participants took a long time to reach a cut-off esophageal temperature of 35.5°C. Although core temperatures did not differ significantly over a few days, these small indicators confirmed changes in cold tolerance.
Life and death in cells
Interestingly, at cold temperatures (below 33°C), both autophagy and apoptotic signals rise after adaptation.
This double response means that the cell was trying to survive using all the tools available. When stress exceeded a certain threshold, enhancing autophagy was not sufficient to prevent some cells from progressing towards death.
This reflects the findings of animal models where excessive autophagy can cause cell death if the damage is too severe.
Take it home? Cold adaptation increases protection, but it is not a magical shield against extreme stress.
Cold plunge can slow cell aging
“I was surprised to see how quickly my body adapted,” King said. “Cold exposure can even prevent disease and slow aging at the cellular level. It’s like tuning the body’s microscope machine.”
The study focused on healthy young men, but opens the door for a wider investigation.
Can older people benefit from structured cold exposure? What about people with chronic diseases that impair autophagy?
These are the next steps scientists want to explore.
Cold Exposure as a Health Practice
This study presents a powerful case for integrating safe and structured cold exposures into wellness routines.
An hour soak for 7 days changed the way the cells handled the stress, repaired themselves, and avoided damage. This is one of the first studies showing these changes at the molecular level of humans.
More research will help define guidelines: cold, how long, how often. But one thing is clear – the body learns. And if you are exposed carefully, colds are not something to avoid, they are something to use.
Whether you are an athlete or someone interested in longevity, this study suggests that the answer may be invisible.
This study is published in the journal Advanced Biology.
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