Cold Shock Proteins: What Happens to Your Cells During Cold Water Immersion

But there's another class of stress responders that are activated when things get chilly fast: cold shock proteins.

Both heat and cold shock proteins fall under the umbrella of stress response proteins. They help your cells adapt to sudden changes in the environment — like swings in temperature — but they’re not the same.

Heat shock proteins (HSPs) kick in when the body heats up, helping to refold damaged proteins and maintain cellular function under stress. I’ll go into more detail on those in a future post.

For now, let’s focus on their colder cousins: cold shock proteins (CSPs). 

These are activated when your body is suddenly exposed to cold — like during a dip in icy water. Their main role is to protect your cells at low temperatures, stabilising RNA and keeping protein production going when things could otherwise grind to a halt.

🧬 The Cellular Factory in Cold Water
Every cell in your body is like a little factory, full of equipment that needs to keep running smoothly — even when the environment shifts suddenly. 

When you begin cold water immersion (CWI), one of the first responses is a rapid boost in mitochondrial activity.

Mitochondria are the powerhouses of your cells — they generate energy and produce heat. Not only do they meet your body’s immediate needs, but regular cold exposure can lead to mitochondrial biogenesis — meaning your body starts making more of them. That’s one of the ways people adapt to cold over time. More mitochondria = better energy production, more internal heat, and greater resilience. When you have more mitochondria you have more energy you burn more calories!

But mitochondria don’t work alone. They’re supported by cold shock proteins, which help ensure the whole system keeps functioning. 

❄️ Meet YBX1: The Cold Shock Protein Doing Big Things
One of the most interesting cold shock proteins in humans is called YBX1. It’s been shown to help cells survive under cold stress in several key ways:

It supports DNA repair and maintenance — vital for long-term cellular health.

It plays a role in the "browning" of fat — converting white adipose tissue (WAT) (which stores energy) into brown adipose tissue (BAT) (which burns energy to produce heat). That means more good fat and better thermoregulation.

It may even influence tumour growth, although this area is still under investigation.

YBX1 isn’t working in isolation, but it’s a standout example of how your body responds at the molecular level to cold exposure.

🧊 Why This Matters for Your Health
When you expose yourself to cold, whether through sea dips, cold showers, or ice baths, you’re doing more than braving the elements — you’re training your cells to respond, adapt, and grow stronger.

Cold shock proteins like YBX1 and the rise in mitochondrial numbers are both part of a broader adaptive response that supports:

Better temperature regulation

Improved energy production

Enhanced fat metabolism

Cellular repair and resilience

So next time you're in waist-deep in cold water thinking "WHAT THE HELL AM I DOING?" , remember — you’re not just toughing it out. You're triggering a cascade of biological upgrades that go far beyond the surface.