Cold exposure – the science

by | May 23, 2024

Key takeaways

  • Cold exposure can be any of the following: cold showers, ice baths, cold water immersion, swimming in cold water and cryotherapy
  • How cold? This will vary based on your current health situation, your sex and how long you have to stay immersed
  • Benefits of this type of hormetic stress include improved mood, relief of peri and post-menopause symptoms, better immunity, increased metabolism exercise recovery, reduced inflammation and enhanced resilience to stress

With winter fast approaching, the benefits of natural cold exposure can more easily be explored for free. In this article, I outline the types of cold exposure, the benefits, the cautions and how to get started.

 

What is cold exposure?

 

Cold exposure refers to the practice of subjecting your body to cold temperatures for short periods, with the intention of eliciting physiological responses for short-term and long-term health benefits.

This can be achieved through various methods such as:

  • cold showers
  • ice baths
  • swimming in cold water
  • cryotherapy

 

What are the scientifically proven health benefits of cold exposure?

 

Enhances mood and focus whilst reducing depressive symptoms

Short-term exposure to the cold increases the release of mood-boosting neurotransmitters. Dopamine post-cold exposure increases by 2.5 times to pre-exposure levels. Dopamine, the famous and powerful molecule that can elevate our mood, focus, and attention and get us moving towards our goals. Adrenalin is immediately produced in response to cold exposure, helping your brain and body prepare to perform and focus. A subsequent benefit is an anxiety-balancing effect.

Additionally, the challenge of enduring cold exposure can enhance mental toughness and resilience, contributing to better stress management and emotional well-being.

Research also shows that cold showers relieve depressive symptoms in part, believed to be due to the high concentration of cold receptors in the skin, allowing an overwhelming amount of electrical impulses from peripheral nerve endings to the brain, having an antidepressant effect.

 

Better immunity

Regular cold exposure, even for a couple of minutes, can stimulate leukocytes that fight off infection. One randomised controlled trial in the northern hemisphere found that people who endured short bursts of cold showers for 90 days had 29% fewer sick days within those 90 days than people who didn’t have cold showers.

However, an interesting biological sex difference was shown when looking at the occurrence of illness at 90 days follow-up, with males showing less reported illness compared to females.

 

Increased metabolism

Cold exposure can stimulate your body to make a rare type of ‘good’ fat, also called brown fat or brown adipose tissue.

Having more brown adipose tissue means a host of benefits for your body, like:

  • Helps burn fat, because increasing brown adipose tissue can reduce the amount of white fat (adipose tissue), which in excess, contributes to inflammation, obesity and insulin resistance
  • Being better able to regulate your body temperature in either hot or cold weather
  • Helping you generate more heat, hence you can improve your tolerance to cold temperatures. A wonderful benefit for those who identify as cold-intolerant
  • Being able to improve your tolerance to sugar (glucose). This is a very good thing given the sugary food we are usually surrounded with, and mostly tend to eat too much of

New research has shown in men that simply immersing in cold water once a week, and having a few cold (only 30 seconds) showers, all other things like diet being equal, can drop centimetres off their middle (ladies, let’s cross our fingers they can see this same result for us in a future study. In this study the women got a host of benefits, but no fat reduction results that were measured!)

A key hack to enhance these benefits is to let your body warm slowly (with only the help of either movement, clothing or blankets) for 10 minutes after exposure. So wait 10 mins before you jump in that hot shower or sauna.

 

Reduced inflammation

Cold exposure has acute anti-inflammatory effects, which can be particularly beneficial for individuals with chronic inflammatory conditions such as gout arthritis. The cold can help to reduce swelling and pain by constricting blood vessels and decreasing metabolic processes that can lead to inflammation.

 

Exercise recovery

Studies have shown that cold therapy after exercise can reduce delayed onset muscle soreness (DOMS), microdamage and inflammation. It’s worth noting that if your workout goal is to build muscle power and strength, ice bathing may not be your friend. It has been shown that it limits the hormetic (good stress) response from exercise, which is the driver of muscular adaptation.

Male and female bodies stand to benefit differently from cold exposure post-exercise. Cold water therapy has a circulatory benefit because our bodies respond by redistributing the blood from the skin back into circulation through the muscles.

As female physiology expert Stacy T Sims, PhD asserts “Men don’t necessarily need this, because their blood vessels naturally constrict post-exercise to push blood away from the skin and back into the central circulation. Women on the other hand tend to vasodilate after exercise, meaning our blood tends to pool in our skin, dropping blood pressure and reducing blood flow to the damaged muscle. Cold water immersion for women can help speed up vasoconstriction after hard exertion, to get blood back centrally helping to increase blood pressure and circulation into the muscles.”

 

Enhanced resilience to stress

Cold exposure is an example of hormesis, a biological phenomenon where a beneficial effect results from exposure to low doses of an agent that’s otherwise harmful at higher doses.

Repeated cold exposure leads to adaptive responses in the body, improving its ability to withstand cold and stress. As a result, individuals who regularly practise cold exposure may find themselves better equipped to handle life’s stressors, both physically and mentally.

 

Pre-operative resilience

Did you know that being anaesthetised during an operation blocks parts of your nervous system that work hard to regulate temperature? This is often the reason hyperthermia is one of the biggest risks of going under the knife.

Anaesthetist and founder of chilluk.org, Dr Mark Harper has been curious about how preoperative, deliberate cold exposure could help strengthen the nervous system and train it not to overreact to hyperthermia.

He says “while this stress response has evolved to protect and heal us, following surgery it overreacts, which can exacerbate the adverse effects of hypothermia.”. He suggests that in his experience cold sea immersion (swimming in his case) can improve surgical outcomes.

 

Relief of perimenopausal and postmenopausal symptoms

The first-ever study into the effect of cold water swimming on women’s hormonal symptoms was published in January 2024. It found that cold water swimming reduced their menstrual symptoms, notably psychological symptoms such as anxiety (47%), mood swings (38%) and irritability (38%). Perimenopausal women reported a significant improvement in anxiety (47%), mood swings (35%), low mood (31%) and hot flushes (30%). The majority of women with symptoms swam specifically to reduce these symptoms (56% for period and 63% for perimenopause symptoms). Women were then asked if they feel the effect of the cold water is increased when the water is colder. The majority of women stated yes (60%).

 

Is it a good idea for me to use cold exposure techniques?

 

The scientific understanding of cold exposure is continually evolving, with ongoing research exploring its benefits, risks, and the mechanisms behind its effects on human health.

While the benefits of cold exposure can be significant, it’s important to approach this practice with caution and awareness of your limits and health status. Gradual adaptation, listening to your body, and seeking medical advice if necessary are key to safely incorporating cold exposure into your health optimisation routine.

Cold exposure checklist:

  • Health status: If you have cardiovascular issues, high blood pressure, or a chronic medical condition, consult your healthcare provider before starting. The shock of cold water can be a significant stressor on the heart and circulatory system
  • Acclimatisation: If you’re new to cold exposure, start with shorter durations and less intense cold, gradually building up your tolerance. This helps prevent shock and reduces the risk of hypothermia. If you’re plunging into a body of water, always have a safety buddy with you
  • Listen to your body: While discomfort is expected, you should never push yourself to the point of pain or distress. Keep cold plunges brief (a few minutes can be sufficient), and always listen to your body’s signals
  • Aftercare: Warm up gradually after cold exposure. Gentle movement, dressing warmly,or simply enjoying a warm drink can help your body return to its normal temperature safely. Some studies show benefits in waiting 10 minutes to use the steam room or sauna
  • Temperature: Female bodies stand to benefit from water as cold as 16 degrees celsius or less, whilst male bodies need it much colder, around 5 degrees celsius to have the same effect. Be aware of how you’re feeling, and if it feels beyond uncomfortable, review what might be most beneficial for you
  • Timeframe: 3 to 5 minutes is enough time to reap the benefits. Start with as little time as you can stand, then gradually increase as you build up tolerance. Be mindful that a 15 min immersion at 5°C is likely to cause body cooling-related problems so care should always be taken when immersing or swimming in cold water
  • Be mindful of your goals: Elite athletes aiming for strength and power may find other hormesis protocols more beneficial or may need adapted cold protocols because studies suggest that cold exposure immediately after resistance training may blunt muscle adaptations. In contrast, cold exposure after endurance exercises, such as cycling or long-distance running, may improve muscle recovery and performance

 

Ways to achieve cold exposure – even if you don’t have a cold plunge’

 

Whilst an effective way to get cold exposure is with a cold plunge pool, if you don’t have access to a cold plunge, there are several alternative methods to achieve similar benefits through cold exposure. These alternatives can be easily incorporated into your routine without the need for specialised equipment:

  • Cold showers: Begin with your usual warm shower and gradually decrease the water temperature until it’s cold. You can start with a few seconds of cold water and gradually increase the duration over-time
  • Ice baths: Fill your bathtub with cold water and add ice until you reach a desired cold temperature. You can start with 1-2 minutes of immersion and move to longer over time. The amount of ice can be adjusted based on your tolerance level
  • Swimming in cold water: Natural bodies of water such as lakes, rivers, or the ocean can provide a natural and refreshing cold plunge experience, depending on the climate and season
  • Using cold packs or wraps: Applying cold packs or wraps to specific areas of the body can provide localised cold exposure benefits, such as reducing core body temperature quickly, reducing inflammation and resultant muscle soreness

 

What temperature should water be for effective cold water therapy?

 

Research shows female bodies start shivering and have related autonomic responses at about 16 degrees celsius, whereas male physiology will only respond as low as 5 degrees celsius. When it comes to the cold plunge guys, you’ll likely need it a bit colder and for women, a bit warmer for the same autonomic response.

 

How long should I stay in cold water for cold exposure to be effective?

 

The effective duration can vary based on individual tolerance and the specific benefits you’re seeking. Generally, a cold plunge or cold shower for 2 to 5 minutes is sufficient to stimulate the body’s adaptive response.

If you are swimming you may be able to handle longer timeframes such as 15-30 minutes.

It’s important to listen to your body and gradually increase exposure time as you become more accustomed to the cold.

 

How often should I practise cold exposure for the best results?

 

Consistency is key for reaping the benefits of cold exposure. However, as to how frequently, discuss with your healthcare practitioner. Some studies show benefits with as little as 3 minutes a week.

Frequency can be adjusted based on your personal goals, tolerance, and response up to 3 times a week, or a frequency that works for your body.

 

The bottom line

Overall the science shows cold exposure can bring with it a suite of health benefits. However you choose to try it, keep it safe, keep it brief and if you’re unsure if it’s safe for you, talk to your healthcare practitioner first.

 

Further reading and podcasts

 

Podcasts
The New Science of Cold Exposure: Reduce Stress, Boost Immunity & Increase Resilience with Dr Susanna Søberg
Dr. Mark Harper: Cold Water Swimming is a Remedy for Overall Body Health
Huberman Lab: Using Deliberate Cold Exposure for Health and Performance

Book
The Cold Water Swim Cure – A Transformative Guide to Renew Your Body and Mind

Further learning
Heat and cold for female physiology and performance by Stacy T Sims PhD

Liv Brown

After spending 15 years in corporate life as a senior marketer it was stress-triggered health challenges, family priorities and a yearning for change that led her to leave her job, driven by a desire to heal herself and help others in a more profound way using her lived experience.