Exploring cold exposure
Should we be embracing cold?
Might a little discomfort be a good thing? Is the insulation that clothes, houses and central heating brings depriving us of a physiological flexibility and a level of resilience that being cold helps us nurture?
Might we benefit from welcoming the cold rather than shunning it?
There is much about our world that is disturbing; there are people suffering from malnutrition due to too much of the wrong food, whilst others suffer from malnutrition due to not enough food of any kind. Similarly, with cold exposure; whilst there are many struggling to heat their homes or stay warm without a home, there are many whose health may be being affected by never being cold thanks to warm clothing and constant use of central heating. For those of us with the good fortune to be able to choose whether to be warm or cold, there might well be health benefits in choosing to be cold regularly for short periods of time.
Cold, when it can be managed, is a hormetic stressor; something we used to experience regularly that causes a generally tolerable level of physiological and psychological stress. We have simply stunning physiological mechanisms inbuilt to deal with this because, certainly in the northern hemisphere and until very recently in our evolutionary history, cold has been a part of our human experience.
Being cold triggers a cascade of mechanisms aimed at maintaining core body temperature
If our core body temperature drops too low (below 35°C) cell function starts to go wrong, so our body has mechanisms it enlists to maintain core temperature in the cold. Cold exposure alters:
neurotransmitter levels, particularly norepinephrine, but also dopamine and cortisol,
heart rate,
the way we breathe (affecting blood carbon dioxide levels and oxygen exchange),
blood vessel function, causing them to contract to conserve core body temperature, resulting in lower temperatures at the periphery,
a rapid up-regulation of metabolic function, both in metabolically active brown fat and in skeletal muscles (shivering) to produce more heat,
immune function.
We are on the edge of understanding more about the possibility that regularly inducing these processes by exposing ourselves to cold may have health benefits and failing to do so may contribute to health issues.
Potential benefits of cold exposure
Through the work of Wim Hof, Susanna Soberg, Magnus Appelberg and others, the possible benefits of regularly engaging in cold exposure are starting to be explored scientifically and these include:
reduced inflammation,
improved cardiovascular health,
improved mood and cognitive function,
improved sleep,
upregulated brown fat metabolism during cold exposure,
beneficial changes in breathing habits to manipulate blood carbon dioxide levels to bring about different physiological responses during cold exposure,
the possibility of influencing elements of our physiology over which it was previously thought we had no control,
cross stress adaptation; the resilience built through regular cold exposure can help us to become more resilient in the face of other life stressors.
What do we mean by cold exposure?
Most importantly, do NOT try cold exposure without first doing your own research into cold exposure and the risks in relation to you and your particular health situation. Cold exposure can and does bring about rapid physiological changes, including changes in breathing, blood pressure and heart rate. In certain circumstances, this can be dangerous. Keep yourself safe.
Having said that, even lowering the temperature of your bedroom to around 19°C or lower at night can bring health benefits. Wim Hof’s method talks through ending your showers daily with a cold shower (even for just 30 seconds), having prepared first with breathing exercises. Some people join a cold water bathing or swimming group, where more experienced people can guide you through this incredible, empowering and enlivening experience. For the reasons mentioned above, don’t go cold water swimming alone. And there is no need to be macho about this; even water at 15°C can trigger the bodily responses that are starting to be associated with health benefits. You don’t need to sit in a bath of ice to benefit (unless you want to).
The scientific research around this is still in its infancy, but I am curious about this practice because being cold regularly is something we have only very recently in our evolution stopped doing. It makes sense to me that we may be losing some physiological skill and agility by no longer being cold.
There has been a great deal of interest in Susanna Soberg’s recent paper on this topic, which investigated brown fat activity (metabolically active fat) specifically in relation to cold exposure. Cold exposure could be an easy way to improve metabolic function via shifting brown fat activity. I have reviewed this study in some detail and it confirms that humans are complicated and difficult to study and that it will be some time before we fully understand in detail what cold exposure does for us healthwise. Soberg’s study looked at a small cohort of fit young men, half of whom were Winter swimmers (and sauna users) and half of whom were not. Of primary interest was whether metabolically active brown fat in Winter swimmers behaved differently in relation to glucose uptake compared to the control group. The issues to be aware of with the study include:
A small cohort (8 people in each group) which limits the extent to which we can rely on the findings.
The cohort consisted of young healthy males, meaning we can’t really extrapolate the findings to females, older people or less healthy people.
The Winter swimmer group had warmer skin around their collar bones (a site of brown fat deposition) compared to the control group when they were exposed to cold and this measure was taken as an indicator of brown fat metabolic activity. However, this increased heat-producing activity in the Winter swimmers could not be associated with increased glucose intake. Skin temperature around the clavicles may not be a good indicator of brown fat activity, alone, but could be indicating skeletal muscle activity and increased circulation of heat via the blood from other organs as a means of generating heat. And brown fat might not be using glucose as its only fuel.
Brown fat metabolic activity increased during cooling in both groups, but there was no significant difference between the groups in glucose uptake as a measure of this. Soberg points out that brown fat uses free fatty acids as an energy source as well as (and possibly in priority to) glucose. It seems likely that in future research, fatty acid uptake of brown fat for fuel will need to be measured.
During a phase of the study where the participants were experiencing a temperature that they considered to be neither warm nor cold, the control group’s brown fat took up glucose, whilst the Winter swimmers’ brown fat did not. Whilst something was going on in Winter swimmers during cold exposure to increase skin temperature around the clavicles more than in the control group, their brown fat was consuming less glucose when they were not cold compared to the control group.
One winter swimmer showed no change in brown fat metabolic activity when exposed to cold and their results were excluded. This suggests that some young men’s brown fat doesn’t respond to cold exposure in the way that others do and that they might be relying upon other mechanisms to generate heat. This warrants further investigation.
The Winter swimmers had a lower core body temperature over a 24hour period compared to the controls.
The experimental group were not only Winter swimmers, but also sauna users too and we know that sauna use can improve ability to transport heat to the skin surface (vasodilation) and sweating ability. This can lead to a lower core body temperature over time and to other physiological differences. It is possible some of the differences seen between the Winter swimmers and the control group here are actually to do with the impact of long term sauna use, not cold exposure.
The differences, such as they are, between the controls and the Winter swimmers that have been shown by this study may not be exclusively to do with Winter swimming, but to do with other lifestyle factors that people who choose to Winter swim might indulge in but that people who don’t fancy Winter swimming do not. It might also be that Winter swimmers are a distinct self-selecting group that have a particular underlying physiology that existed before they started Winter swimming.
This is a complicated area and designing research to study it is challenging. We will learn more as we go along. We we can’t really conclude much healthwise from this study, so practicing cold exposure solely to upregulate your metabolism via increased brown fat activity based on this study would be misguided.
The most enlightening things about all this? Well, for me, anyway, it has been, firstly, about appreciating that research in this area truly is in its infancy. And secondly that experiencing cold exposure has been useful in fostering resilience and a greater capacity to have a handle upon part of my physical world driven by subconscious forces. Whilst we are wired to shrink away from the cold, it is, in truth, just sensory information received by our nerves, just as warm is. And as it turns out, we do have some control over how we respond to this information. Being able to, over time, modulate my response to the sensory experience that is cold really opens the door to having the flex to choose how I respond to other stressors in my life. And for now, that carries enough potential benefits to make me want to continue.
By Jo Webster
