The Scientific Evidence on Cold Showers
The feeling you experience when immersing yourself into extremely cold temperatures of any substance are often compared to electroshock therapy.
This is due to an increased activity of the sympathetic nervous system, which is commonly known for the fight-or-flight response¹.
In this case, it sends a signal of flight: “You’d better get out of there!”
If this is the case, why do some people inflict such short-term misery onto themselves? What are the true benefits?
Let’s dive into the science!
Several years ago, the hype of taking cold showers as cryotherapy (“cold therapy”) accumulated to subsequently decline rapidly after scientific evidence of its benefits were minimal.
While the perceived subjective benefits are clear and often elaborated on, in this writing I shall state the staunch scientific evidence built up through the years on the benefits of taking cold showers.
This includes a take on metabolism, blood circulation, energy, dermatology, immunity, stress, and anxiety & depression.
1. Metabolism
Metabolism is the biochemical process of converting consumed nutrition in combination with oxygen into energy that we use for a large variety of bodily functions, such as keeping your body operating (breathing and blood flow) or recovering it from prior damage (cell and tissue repair).
Another component the body uses energy for is its internal heating system. This system can be stimulated by the immersion of the body into chilly environments, such as cold water.
But, how does this work?
Well, cold water has the effect of causing you to shiver, which uses up energy to keep the body temperature regulated.¹ ²
Put differently, it wakes up your internal heating system.
This is equivalent to an increase in short-term metabolism. Which, in turn, increases the rate of calories burned and improves the body’s ability to function efficiently.³
Now, for scientific evidence we have to look at Brown Adipose Tissue (BAT). BAT is considered the “good fat” used to heat up our internal stove and protect us against the cold.⁴ ⁵ An increase in BAT results in higher energy expenditure (or metabolism).⁶
So how do we increase BAT?
The evidence isn’t 100% clear, but cold exposure is receiving accumulating attention as a causal factor of the creation of BAT.⁷
For example, researchers found the inverse correlation between BAT activity and shivering, linking BAT with metabolism.⁸
Furthermore, it was observed that this substance is inversely correlated with BMI.⁹
So, even though the bulk of evidence is minor, scientific evidence points at cold showers having a positive effect on your metabolism.
2. Increased Circulation
Marybetts Sinclair, in her book titled “Modern Hydrotherapy for the Massage Therapist”, states that the touch of cold water onto the bare skin has the effect of improving, besides the nervous system, the circulatory system.¹⁰
A stimulation of the circulatory system signifies an increment in blood flow.
This is of major importance for the transportation of blood, nutrients and oxygen through the body, while getting rid of waste products such as carbon dioxide.
Besides these benefits, it is said to improve muscle recovery.
In their meta research on cryotherapy for preventing and treating muscle soreness after exercise, C. Bleakley et al. found statistically significant effects in reduced muscle soreness and fatigue, while potentially increasing physical recovery ratings.¹¹
Hence, the stimulation of the circulatory system has various potential benefits to the functioning of the human body.
3. Increased Alertness (energy boost)
As described earlier, cold water immersion has the effect of a surge in oxygen intake and an escalation of the heart rate. This in turn affects the brain in a multitude of ways, which can be explained by introducing the chemical norepinephrine.
Norepinephrine behaves as a neurotransmitter which is released in the blood in the event of perceived stress. It is also a hormone with various consequences attached to it, but this is beyond the scope of this writing.
Research has shown that cold exposure results in an accumulation of “…neuronal activity, most specifically the enhancement of hormonal, autonomic and behavioral responses to acute stressful stimuli.”¹²
In other words, it increases neural activity, awareness and alertness.
Furthermore, Huttunen, Kokko and Ylijukuri conducted an experiment where individuals were asked to go for a swim in cold water on a daily basis for the duration of four months.¹³
They were shocked to find out that the participants’ short-term tension, fatigue, memory and mood were negatively affected, rejecting their initial hypothesis.
However, after the four month period, the participants had statistically significant higher vigor scores and reported higher levels of energy and briskness.
Combining extant research found, we can conclude that the short-term benefits are merely found in the area of increased cognition, arriving jointly with increased fatigue and reduced mood.
The long term benefits are composed of an increase in vitality, awareness, and neural activity. In short: you feel awake and alive.
4. Skin & Hair
Even though the benefits of cold showers on your skin and hair are limited, inferences can be drawn between the cause and effect.
In her book titled “How to Get Clear Skin”, Dr. Jacqueline Schaffer identified that the constriction of blood flow due to cold immersion results in a healthier skin glow.¹⁴
Furthermore, aesthetic doctor Dr. Michael Barnish stated that the touch of cold water shrinks the skin’s pores, resulting in an improvement of “the overall texture and appearance of the skin.”
On a similar note, Jessie Cheung, MD, a dermatologist in the Chicago area, noted that cold water constricts blood vessels, decreasing redness and puffiness of the skin.
However, the scientific evidence on this part appears to be lacking.
The arguments provided by above-mentioned “experts” all refer to the beneficial effects of increased blood circulation caused by cold water immersion.
As such, we note a chain of cause of effect: cold water increases blood circulation, which in turn has various consequences for the skin and hair.
Without further scientific evidence, we shall move on.
5. Increased Immunity
“The more voluntary suffering you build into your life, the less involuntary suffering will affect your life” — Tim Ferriss
In a randomized controlled study in 2016, a randomly selected group of 3,018 participants between the ages of 18 and 65 were asked to take daily cold showers for a period of three months. The instigators of this research were to investigate the effect of these routine cold showers on, a.o., sickness.¹⁵
The results were eye-opening: participants who finished the 90-day trial showed a 29% reduction in sickness absence compared to the control group. A clear indication of a strengthening immune system.
It can be argued that this is due to an increase in red blood cells, white blood cells, and platelets upon cold water immersion as found in a 2011 study on cold water swimming.¹⁶
A similar study found that cold water swimming resulted in an increase in the baseline concentration of reduced and oxidized glutathione, which functions as an antioxidant preventing damage to important cellular components.¹⁷
This is some form of so-called body hardening, increasing tolerance to malicious bacteria and diseases.
The results were supported in a subsequent experiment, concluding that this adaptive response can be seen as “a new basic molecular mechanism of increased tolerance to environmental stress.”¹⁸
As such, scientific evidence concurs on the positive effect of cold water immersion on the body’s immune system.
6. Reducing anxiety and depression
As mentioned in the introduction of this writing, cold showers can have a shocking experience similar to electroshock therapy.
Nowadays called electroconvulsive therapy, this practice induces seizures in the brain to provide consolation from mental disarray.
So it wouldn’t be too surprising that cold showers have a similar effect, no?
In an experiment conducted in 2008, Nikolai A. Shevchuk let participants take a 2–3 minute cold shower.¹⁹ The results show that this practice indeed does resemble the results of electroconvulsive therapy!
Depressive symptoms were reduced, pain was relieved, and no further side-effect were found.
Note that the amount of research on this front is minimal; the author recommends further research is required to validate this theory.
So where does this leave us?
In short, the volume of scientific evidence on the response of our body to cold water immersion is limited.
I can personally imagine the difficulty to recruit voluntary participants to take daily cold showers.
Despite this limitation, to a large extend, we can agree upon the following:
Cold showers
- Increase short-term metabolism;
- Stimulates blood flow;
- Surges awareness and alertness;
- Polishes hair and skin;
- Reinforces the immunity system; and
- Reduces anxiety and depression;
This should be plenty the stimulus to face the refreshing cold water when undertaking a shower session.
As the popular Chinese proverb goes:
“The best time to plant a tree was 20 years ago. The second best time is now.”
So, let’s start today, shall we?
Sources
[1] P. Srámek, M. Simecková, L. Janský, J. Javlíková, and S. Vybíral (2000). Human physiological responses to immersion into water of different temperatures. European Journal of Applied Physiology.
[2] A.A.J.J. van der Lans et al. (2013). Cold acclimation recruits human brown fat and increases nonshivering thermogenesis. The Journal of Clinical Investigation.
[3] P. Lee et al. (2014). Irisin and FGF21 are cold-induced endocrine activators of brown fat function in humans. Cell Metabolism.
[4] A. Bartelt and J. Heeren (2013). Adipose tissue browning and metabolic health. Nature Reviews Endocrinology.
[5] M. Rossato et al. (2014). Human white adipocytes express the cold receptor TRPM8 which activation induces UCP1 expression, mitchondrial activation and heat production. Molecur and Cellular Endocrinology.
[6] M. Rosenwald and C. Wolfrum (2013). The origin and definition of brite versus white and classical brown adipocytes. Adipocyte.
[7] C.L. Coolbaugh, B.M. Damon, E.C. Bush, E.B. Welch, and T.F. Towse. Cold exposure induces dynamic, heterogeneous alterations in human brown adipose tissue lipid content. Nature.
[8] V. Ouellet et al. (2012). Brown adipose tissue oxidative metabolism contributes to energy expenditure during acute cold exposure in humans. Journal of Clinical Investigation.
[9] A.M. Cypess, M.D., Ph.D. et al. (2009). Identification and importance of brown adipose tissue in adult humans. The New England Journal of Medicine.
[10] M. Sinclair (2007). Modern hydrotherapy for the massage therapist.
[11] C.M. Bleakley and G.W. Davison (2010). What is the biochemical and physiological rationale for using cold-water immersion in sports recovery? A systematic review. British Journal of Sports Medicine.
[12] D.M. Buffalari and A.A. Grace (2009). Chronic cold stress increases excitatory effects of norepinephrine on spontaneous and evoked activity of basolateral amygdala neurons. International Journal of Neuropsychopharmacology.
[13] P. Huttunen, L. Kokko, and V. Ylijukuri (2004). Winter swimming improves general well-being. International Journal of Circumpolar Health.
[14] J. Schaffer, M.D. (2019). How to get clear skin: A complete guide for clear, radiant, youthful skin.
[15] G.A. Buijze, I.N. Sierevelt, B.C.J.M. van der Heijden, M.G. Dijkgraaf, and M.H.W. Frings-Dresen. The effect of cold showering on health and work: A randomized controlled trial. PLoS One.
[16] G. Lombardi, C. Ricci, and G. Banfi (2011). Effect of winter swimming on haematological paramters. Biochemia Medica.
[17] W.G. Siems, F.J.G.M. van Kuijk, R. Maass, and R. Brenke (1994). Uric acid and glutathione levels during short-term whole body cold exposure. Free Radical Biology and Medicine.
[18] W.G. Siems, R. Brenke, O. Sommerburg, and T. Grune (1999). Improved antioxidative protection in winter swimmers. International Journal of Medicine.
[19] N.A. Shevchuk (2008). Adapted cold shower as a potential treatment for depression. Medical Hypotheses.
