I’ve been around for long enough to see health trends come and go, but cold therapy is one that has staying power. Humans have probably been using cold water to treat injury and illness, wake up their senses, and challenge their physical fortitude for all of human history. The modern obsession with cold plunges, cryotherapy chambers, and sitting underclothed in the snow doing controlled hyperventilation (a la “The Iceman” Wim Hof and his eponymous method of breathwork paired with extreme cold endurance feats) is just the newest iteration. There is something fundamental about the relationship between humans and the cold.
Of course, Grok and kin weren’t taking cold showers to stimulate the immune system or revive senses dulled by hours and years of participating in corporate drudgery. They were washing in cold rivers and wading into the ocean to trap sea creatures out of necessity. But the effect was the same as when we modern humans do a polar bear plunge—a stronger, more robust body.
Today, most of us enjoy (or rather, suffer from) round-the-clock thermally controlled environments. We’re rarely ever truly cold, not that bone-chilling, teeth-chattering cold where you wonder if you’ll ever feel warm again. Not unless we go out of our way to get uncomfortable.
Many people in fact claim to hate the cold. I admittedly did my fair share of grumbling about having to face frigid mornings as a kid growing up in Maine. But as anyone who has taken the time to embrace the cold knows, once you get used to it, your body actually craves the cold. Like so many things that are uncomfortable in the moment, it’s good for you in the long run. Your body knows that on a cell-deep level.
At the same time, there is a lot of academic debate about the limitations of cold exposure and cold therapy. Promoters of cold water therapy say that it can boost immune function, decrease inflammation and pain, and increase blood flow. Skeptics wonder if it’s all it’s cracked up to be. Some go so far as to argue that it does more harm than good in certain circumstances. Let’s explore.
Types of Cold Therapy
I’d roughly break cold therapy into two categories:
Cold exposure to reduce pain, improve mobility, speed healing, or enhance recovery (acute effects)
Cold exposure for general health and longevity (long-term effects)
“Cryotherapy” is the general term for using cold (“cryo”) to produce health benefits, but you probably associate the word specifically with whole-body chambers that blast you with extremely cold air (typically between -200 and -300 degrees Fahrenheit, or -128 to -184 Celsius). That’s one way to access the benefits of chilling out. You can also
Apply ice packs or cold compresses to targeted areas of the body
Partake in ice massage, getting a rubdown with ice cubes or chilled implements
Use cooling sprays
Take cold showers or contrast showers (alternating hot and cold)
Cold water immersion, or dunking your whole self in very cold water, is popular among the ancestral health crowd and potentially the most beneficial form of cold therapy. This covers anything from your standard ice bath to jumping in a brisk mountain lake to joining your local polar bear club and swimming in frigid water in nothing but your skivvies. For a more controlled cold water immersion experience, you can purchase a cold plunge tank for your home, or go the route of my friend and longtime coauthor Brad Kearns and make your own DIY cold plunge out of a chest freezer.
I’d also put going out in cold weather slightly underdressed in the cold therapy camp. It may not be as actively therapeutic as the other methods, but it does a body good nonetheless.
How Does Cold Therapy Work?
Cold therapy falls under the umbrella of hormetic stressors—stressful stimuli that, when applied appropriately, produce adaptations that make us healthier and more resilient to future challenges. It’s the “that which does not kill you makes you stronger” effect.
The body doesn’t like to be too cold or too hot, preferring to stay in that “just right” zone. Hence, it will actively protect itself against big excursions outside its comfort level. When you expose yourself to cold—especially via cold water or air over your whole body—a number of homeostatic mechanisms kick into gear to keep your core temperature from dropping too low.
Blood vessels near the surface of the body constrict, a process known as cutaneous vasoconstriction. This pulls blood into the core and slows heat loss through the skin.
Stay in the cold water or air long enough, and you’ll start shivering, which produces heat.
Next comes an increase in non-shivering thermogenesis (“thermo”=heat, “genesis”=making). You’ve probably heard of brown fat, the mitochondria-rich, metabolically active fat that generates heat in baby and adult humans alike. Well, cold exposure activates existing brown fat and tells the body to make more brown fat to boot. This translates to increased metabolic rate. Besides producing heat, a sped-up metabolism might enhance recovery following workouts and injury.1 It’s also why some people argue that cold exposure could be the next big weight-loss breakthrough (a somewhat dubious claim I’ll discuss shortly).
Cold also stimulates the immune system, reduces oxidative stress, and triggers a host of favorable hormonal responses.23 For example, it increases norepinephrine levels, which decreases pain sensations, and ACTH (adrenocorticotropic hormone),4 which helps the body respond to stress and regulate blood sugar and blood pressure.
Long-term, repeated exposures to cold improve cold tolerance, which is why those grizzled old-timers in the polar bear club seem to have no trouble jumping into the northern sea despite the ice and slush floating on top. The water literally isn’t as shocking to their systems.
Benefits of Cold Therapy
I’m a fan of cold exposure in general. My interest is mostly related to how it challenges you physically and mentally, making you tougher and perhaps extending healthspan and lifespan, though we can’t say for sure. There are people testing that hypothesis on themselves right now, but those results are decades in the making. In the meantime, I’m thoroughly sold on cold as a hormetic stressor that improves overall well-being.
There are other more immediate benefits too, and some areas where we get it wrong.
Recovery after exercise or injury
The image of a hardcore pro athlete getting into a metal trough of ice water after a big game or meet is burned into the cultural psyche. If you take a spill and twist an ankle or tweak your wrist catching yourself, your first impulse will probably be to ice the injury.
The inclination comes from a good place. Cold blunts pain and reduces inflammation and (sometimes) swelling. However, there is considerable debate about whether icing does more harm than good in the long run, with many experts arguing that you should skip it. I go into greater detail about icing injuries in a separate post, but for now consider that acute inflammation (not the chronic systemic type) is there for a reason. Trying to shoo it away more quickly than the body would naturally do on its own could actually delay healing or compromise the exercise adaptations that make you stronger in the long run.
That said, there are specific cases in which I would apply cold therapies. One is after an injury if the pain is severe and/or the swelling is great enough to potentially impair healing. Be aware, though, that icing can sometimes increase swelling. The second is for athletes who are doing multi-day events and need to deliver another good performance the day after a hard effort. Cold therapy can be useful for delaying the onset of muscle soreness and, perhaps most importantly, offsetting perceptions of fatigue, helping the athlete to believe they are rested and ready to hit the ground running again.5
Otherwise, for athletes who want to expose themselves to cold for general health reasons, I’d recommend partaking in cold plunges or showers far away from the stimulus of workouts—at least several hours after. Besides blunting the adaptive response to workouts, if you have significantly raised your core body temperature during exercise, you don’t want to drastically and dramatically shock it with frigid temps.
Better immunity, less illness
Cold therapy boosts the immune system, stimulating white blood cells, anti-inflammatory cytokines, and natural killer cells that can fight infections and possibly even gobble up tumors. Now, I’m not suggesting that cold showers cure cancer, but there is the possibility that cold therapy could prove an interesting adjuvant treatment down the road.6
One study of over 3,000 people found that those who took cold showers lasting between 30 and 90 seconds for a month reported 29 percent fewer sick days from work compared to those who did not take cold showers.7 Other researchers have found that cold water swimmers have fewer upper respiratory tract infections than their partners who don’t swim.8
Get cold to lose weight?
There’s some evidence that cold exposure—even just staying in a cool room (62 degrees Fahrenheit, 19 Celsius) for a couple hours a day—can significantly increase metabolic rate and energy expenditure, leading to fat loss.9 Influential self-experimenters like author Tim Ferriss and former NASA scientist Ray Cronise swear by using cold to accelerate fat burning. Average people around the world credit cold plunges with helping them lose weight. What gives?
This isn’t just a tabloid hack. When you’re cold, your body expends a lot of energy to maintain homeostasis—up to five times normal resting metabolic rate in extreme cold conditions.10 Much of this comes from shivering, particularly in acute cold.
As I already mentioned, cold exposure also increases your body’s stores of metabolically active brown fat and dials up non-shivering thermogenesis. Simply having more brown fat on board won’t cause that stubborn white fat to melt away, though. You need repeated cold exposures to “turn on” that brown fat so it burns more calories to produce heat. Cold showers or cold plunges would theoretically need to become a regular thing (or just crank the thermostat down for a couple hours each day). Brown fat, when activated, also pulls glucose and fatty acids out of the bloodstream. More brown fat is associated with lower insulin levels and greater insulin sensitivity.11
So there’s something to this idea that cold could facilitate weight loss. Still, I’d hesitate to put this in the forefront of fat reduction techniques. Even as drug companies are spending millions to develop pharmaceuticals to tap into the power of brown fat, ditching grains and sugars, increasing daily movement, and working on sleep and stress are always going to be the big needle movers when it comes to all aspects of health.
Speaking of sleep, many folks claim that cold showers at night help them sleep more deeply and soundly. I haven’t seen studies to back that up, but I would believe that cold showers kickstart the body’s natural nocturnal drop in body temperature that accompanies sleep onset.
This is something you could experiment with yourself. Try an evening shower where you start warm and gradually drop the temperature into a comfortably cool zone. I wouldn’t recommend jumping into an ice bath right before bed because that will spike your cortisol, which isn’t conducive to falling asleep. One exception is possibly for people who, for reasons of schedules or convenience, have to conduct their workouts close to bedtime and hence raise their body temperatures. One study found that male athletes who worked out at 6 p.m. and then hopped into cold water (56 degrees Fahrenheit, 13 Celsius) for 10 minutes slept better than athletes in a control, no cold water condition.12
But wait, there’s more!
These are the main rationale for using cold therapies, but there are many more. Researchers are also interested in whether cold therapy improves cardiovascular health,13 sleep apnea,14 chronic fatigue syndrome,15 depression16… one almost starts to wonder if there’s anything cold can’t do.
Bear in mind, though, that the degree to which cold therapy actually leads to desirable responses and adaptations depends on factors including but not limited to
Type of cold therapy
That’s a lot of nuance to wade through. You can’t just throw a 10-pound bag of ice in your bathtub and assume all your problems will go away. For long-term benefits to accrue, cold exposure probably needs to become part of your regular routine. Much like meditation, you can get positive results from an occasional session here and there, especially when a new issue crops up in your life. However, the people who get the most out of it will be the ones who practice regularly.
Risks of Cold Therapy
I’m certainly in the camp of “cold exposure does some really cool things and generally makes us healthier and heartier.” Most people probably need less comfort in their lives, and cold showers, chilly winter walks, and the occasional cold plunge would do them a lot of good. Don’t be dumb about it, though. Our ancestors spent a lot of time and effort surviving the cold; the least we could do is respect it.
If you’re new to cold therapies, start small. Go for short times at moderately cold temperatures, and build up your tolerance and exposure gradually. Hypothermia is nothing to mess around with. When you go from an ambient temperature to very cold water, your body has a natural cold shock response that can be dangerous, especially for people with preexisting heart conditions. People who have any kind of cardiovascular issue will want to talk to their doctor before starting cold therapy, especially cold water immersion or cryotherapy. Likewise, for acute or chronic injuries, get advice from a pro who can help you craft a smart recovery protocol.
Is It All Just a Placebo Effect?
A lot of the excitement around cold exposure comes from personal anecdotes from citizen scientists around the world. It’s entirely possible that some of the touted benefits they’re experiencing are due to placebo effects.17 In fact, I’d bet on it.
And I’m not saying that’s a bad thing. The mind is a powerful tool, and if it helps us get better just because we believe we can, that’s great. But even if some of it is a product of your own belief system, there are piles of studies showing actual physiological mechanisms that explain or predict the benefits of cold therapy. So no, it’s not just a placebo.
So what say you? Are you already incorporating cold showers, cold plunges, or winter swimming into your healthy lifestyle? If yes, what benefits have you noticed? If no, what’s holding you back?
Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.