Boosting Immunity with Cold Training: The Science Behind Ice Baths and Winter Swims
- Eleonora Patsenker
- Mar 18
- 5 min read
Cold showers, ice baths, winter swimming—some people make them a regular habit, claiming they rarely get sick. While it might seem extreme, research suggests there’s real science behind the connection between cold exposure and a stronger immune system. But what’s actually happening inside the body? How does something as simple as a plunge into icy water help ward off infections? Let’s break it down.
The Immune System: Your Body’s Personal Army
Your immune system is like an elite security team, constantly patrolling to protect you from invaders like viruses, bacteria, and other harmful microbes. It consists of two major branches:
Innate Immunity – The first line of defence. Think of it as border security, ready to neutralize threats on sight. This includes natural killer (NK) cells, macrophages, and neutrophils.
Adaptive Immunity – The strategic mastermind. It creates memory cells (T-cells and B-cells) that “remember” past infections and develop a targeted response, much like a vaccine trains the body to fight specific diseases.
Keeping this system in top shape is essential to ward off illnesses—and cold exposure might just be the workout it needs.
Cold Exposure: The Natural Immune Booster
Science shows that regular cold exposure can modulate both innate and adaptive immunity, acting almost like a natural vaccine. Here’s how:
✔️ Increases White Blood Cells & Natural Killer Cells – A 2016 study found that people who regularly engaged in cold water immersion had higher counts of white blood cells and improved NK cell activity, helping them fight infections more efficiently.
✔️ Enhances Anti-Inflammatory Response – Cold training lowers chronic inflammation, which is linked to many modern diseases. When you expose yourself to cold, your body increases the release of adrenaline and cortisol, which in moderate amounts can help regulate inflammation rather than suppress the immune system.
✔️ Boosts the Production of Cold Shock Proteins – These specialized proteins, such as RNA-binding motif protein 3 (RBM3), help maintain cell integrity, aid in tissue repair, and even improve resilience to neurodegenerative diseases.
✔️ Triggers Hormesis: The Good Stress – Small, controlled stressors like cold exposure make the body more resilient. Your immune system responds by increasing the production of cytokines (immune signalling molecules), enhancing both immediate and long-term immunity.
✔️ Improves Lymphatic Circulation – The lymphatic system is crucial for detoxification and immune function. Cold water immersion promotes lymphatic drainage, helping the body eliminate waste and improving immune surveillance.
Cold Training vs. Vaccination: A Surprising Connection
Just like vaccines train your adaptive immune system to recognize and fight off specific pathogens, cold exposure stimulates an immune response without an actual infection. This controlled exposure to stress improves immune memory, possibly making your body more adaptable to environmental challenges.
Hardcore Science: Mechanisms Behind Cold-Induced Immunity
Key pathways involved in cold-induced immune system activation:
1. Activation of the Sympathetic Nervous System & Catecholamine Release
- Cold exposure stimulates the sympathetic nervous system (SNS), leading to the release of norepinephrine (noradrenaline) and epinephrine (adrenaline).
- Norepinephrine plays a crucial role in reducing inflammation by downregulating pro-inflammatory cytokines such as TNF-α, IL-6, and IL-1β while promoting anti-inflammatory cytokines like IL-10.
2. Hypothalamic-Pituitary-Adrenal (HPA) Axis & Cortisol Release
- Cold stress activates the HPA axis, leading to increased secretion of cortisol, a well-known anti-inflammatory hormone.
- Cortisol inhibits immune overactivation by suppressing excessive cytokine production and dampening immune cell recruitment to inflammatory sites.
3. Modulation of Innate Immune Cells
- Cold exposure influences monocytes and macrophages, reducing their pro-inflammatory activity while increasing their tolerance to inflammatory stimuli.
- It also enhances the activity of natural killer (NK) cells, which play a key role in immune surveillance and help eliminate infected or dysfunctional cells.
4. Vagal Nerve Stimulation & Cholinergic Anti-Inflammatory Pathway
- Cold exposure activates the vagus nerve, which in turn modulates immune function through the cholinergic anti-inflammatory pathway.
- This pathway suppresses excessive inflammation by inhibiting the release of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) through acetylcholine signalling.
5. Cold Shock Proteins & Cellular Stress Response
- Exposure to cold can induce the production of cold shock proteins, such as RNA-binding motif protein 3 (RBM3), which promote cellular resilience and reduce inflammatory damage.
- These proteins help prevent excessive immune activation and protect cells from apoptosis (programmed cell death) caused by chronic inflammation.
6. Enhanced Brown Adipose Tissue (BAT) Activity & Anti-Inflammatory Effects
- Cold exposure stimulates brown adipose tissue (BAT), which releases anti-inflammatory adipokines like IL-4 and IL-10, shifting immune responses towards an anti-inflammatory profile.
- BAT activation also increases fatty acid oxidation, reducing metabolic stress and systemic inflammation.
7. Reduction of Oxidative Stress & Inflammatory Damage
- Cold exposure has been shown to increase antioxidant defences (e.g., superoxide dismutase, catalase, glutathione peroxidase), which help mitigate oxidative stress and prevent excessive inflammatory responses.
- By enhancing mitochondrial function, cold exposure improves cellular metabolism and reduces the accumulation of inflammatory byproducts.
How to Start: A Simple Cold Training Protocol
You don’t need to jump into a frozen lake on day one! Here’s how to safely build your cold resilience:
Cold Showers – Start with 30 seconds of cold water at the end of your regular shower, gradually increasing to 2–3 minutes.
Cold Water Immersion – Try dipping into a cold lake or ice bath for 1–5 minutes, focusing on deep, controlled breathing. Start at around 12-15°C before progressing to lower temperatures.
Winter Swimming – Once comfortable, join a local cold-water swimming group and swim in open water (always prioritize safety!).
Consistency is Key – Aim for at least 2-3 cold exposures per week to see immune benefits.
Warm Up Naturally – After exposure, avoid hot showers; instead, move around and let your body generate heat naturally.
Final Thoughts: Ready to Take the Plunge?
Cold exposure is not just a test of mental toughness—it’s a scientifically backed way to strengthen your immune system, improve resilience, and even enhance mood and energy. With consistent practice, you’ll likely notice fewer colds, faster recovery times, and a greater sense of vitality. So, why to wait?!
Literature:
1. Setor K Kunutsor, Andrea Lehoczki, Jari A Laukkanen. The untapped potential of cold water therapy as part of a lifestyle intervention for promoting healthy aging. GeroScience. 2024 Jul 30;47(1):387–407.
2. Roland Wesołowski, Celestyna Mila-Kierzenkowska, et al. The Influence of Winter Swimming on Oxidative Stress Indicators in the Blood of Healthy Males Metabolites 2023 Jan 17;13(2):143.
3. Tara Cain, Jacinta Brinsley, et al. Effects of cold-water immersion on health and wellbeing: A systematic review and meta-analysis. PLoS One 2025 Jan 29;20(1)
4. Didrik Esperland, Louis de Weerd, et al. Health effects of voluntary exposure to cold water - a continuing subject of debate. Int J Circumpolar Health. 2022 Dec;81(1):2111789.
5. Beat Knechtle, Zbigniew Waśkiewicz, Caio Victor Sousa. Cold Water Swimming—Benefits and Risks: A Narrative Review, Int J Environ Res Public Health. 2020 Dec 2;17(23):8984.
6. I K Brenner, J W Castellani, C Gabaree, et al. Immune changes in humans during cold exposure: effects of prior heating and exercise. J Appl Physiol. 1999 Aug;87(2):699-710.
7. Anouk A J J van der Lans, Mariëtte R Boon, Mariëlle C Haks, et al. Cold acclimation affects immune composition in skeletal muscle of healthy lean subjects. Physiol Rep. 2015 Jul 6;3(7).
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