Cold Plunge vs Sauna: Which One Is Better?

It’s thought that the earliest form of the sauna dates back 10,000 years, found in ancient Islamic practices and Native American sweat lodges. One early version of the concept was the pit sauna: a hole dug into the ground, with a pile of stones heated by a campfire at the bottom. Once the pit was covered with thatch or peat, water was thrown over the hot stones to create steam. 

Since then, the steamy ritual has evolved into a bona fide recovery tool used by elite athletes, biohackers, and everyday people. And although a sauna session may look a little different today, the concept remains the same — by exposing your body to high heat, your core temperature rises, your blood vessels widen, your heart rate speeds up, and you begin to sweat heavily, helping you relax, ease muscle soreness, and support cardiovascular health.

And while cold plunges are seemingly a more modern affair — especially when compared to a tool that’s been around for over 10,000 years — there’s just as much history behind the practice. The Ancient Greek physician Hippocrates suggested that hydrotherapy could ‘allay lassitude’ — reduce the depletion of energy or strength — and, in approximately 3500BC, the Edwin Smith Papyrus made numerous references to cold being used for therapeutic purposes. 

Today, it seems, the research is finally catching up with Hippocrates, as benefits in both heat and cold exposure point to key longevity markers, hormetic mechanisms, and various biological benefits. Speaking to Dr. Adam Staten, a general practitioner with the NHS and Medical Director at One Day Tests, Healf gives the verdict on not only which of the two is worth your time, but how they work and the unique connections each holds with your personal wellbeing. 

How each one actually works — and why the mechanisms matter

Let’s start with the sauna. There’s actually far more to it than simply sweating (a lot). “The exposure to heat in a sauna causes a range of physiological reactions like increased heart rate, dilatation of blood vessels and diversion of blood away from internal organs to the skin and possibly the muscle,” explains Dr. Staten. “This has a range of consequences in the body including reducing blood pressure, increasing the elasticity of the blood vessels, and reducing inflammation.” It’s a similar biological response to what happens during moderate to intense exercise, he continues, describing how these physiological changes are similar to what people try to achieve with other cardio-protective medications, including blood pressure pills and statins. 

On the other side of the equation, cold water immersion (sometimes referred to as CWI), “provokes a physiological response that mimics many of the body's responses to exercise, including a rising heart rate, faster respiration, and release of cortisol and noradrenaline.” Cortisol, often labelled as the stress hormone, helps to regulate your metabolism, controls blood pressure and blood sugar, and drives the natural sleep-wake cycle. Meanwhile, noradrenaline, the fuel behind your fight-or-flight response, is released, boosting alertness and constricting blood vessels to keep your blood pressure stable during high-stress situations or medical emergencies. “This seems to help with reducing post-exercise inflammation and so aids with recovery,” Dr. Staten says. But he also caveats that the full mechanisms by which CWI works are actually not completely clear.

The cardiovascular case: What the research really shows

Walk into any sauna and the first thing you’ll notice — besides the heat — is that everyone is sat still. With the physiological benefits of heat exposure offering a “similar response to intense exercise,” what’s actually happening under the surface? While remaining seated won’t improve your 5K time, it can help your heart health. “The evidence we have seems to suggest an inverse relationship between sauna use and cardiovascular diseases including sudden cardiac death,” Dr. Staten explains. “Another study showed stroke risk reduction of 62% and another showed a reduced risk of Alzheimer's disease of 66%. If this was a preventative pill, we'd consider it to be very effective.” 

That said, “the evidence base isn't huge,” Dr. Staten continues. “A lot of the studies are done in Finland where sauna usage is particularly high, with the average Finn using the sauna two or three times a week.” Apply this 'increased usage' — approximately four to seven times a week — to those in the UK, and the practice becomes a bit less practical. 

The use of CWI is equally insubstantial. “Most research is focussed on athletes and how it facilitates training and recovery,” says Dr. Staten. “At most, studies tend to evaluate the immediate effect of cold water immersion on parameters like blood pressure, rather than the long term effect.” How this translates to the average person and their long term cardiovascular health, he explains, “isn't really clear yet.”

Recovery, inflammation and the cold-heat debate

The recovery question is where things get murkier. Both sauna and cold water immersion have, in some studies, been shown to subjectively reduce muscle soreness after exercise, though cold water immersion has the edge on paper: “it has been shown to reduce levels of markers of muscle damage or stress like lactate or creatine kinase, which suggests it is effective at reducing muscle inflammation.”

But Dr. Staten also points out that there isn't a ton of high quality research into this debate, and that the ones that do exist tend to be small and “at risk of bias.”

There’s also the fact that frequently exposing your body to cold temperatures while trying to recover post-workout may actually impair the development of muscle, power, and strength, points out Dr. Staten. Inflammation exists for a reason. “There is a biological purpose to the inflammatory response, and some emerging evidence seems to suggest that constantly suppressing this response may enable you to train harder in the short term, but limits gains in the long term.”

Mood, mental health and the hormetic stress connection

​​Mood is even harder to pin down than muscle inflammation. Dr. Staten explains: “This is another area where the scientific data is a bit sparse,” he says. It's generally accepted that saunas are enjoyable, relaxing, and great social spaces, all of which would suggest they're good for mental health, but that’s more anecdotal versus proven out in lab studies.  

Cold water carries a similar problem, muddied further by confounding factors. “There are studies suggesting that CWI can improve overall wellbeing,” Dr. Staten notes, “but the studies often investigate CWI in a context where there are other confounding factors like people who do wild swimming, where the mental benefits may be from the whole experience rather than just a response to CWI.”

The verdict: should you choose one, or is the combination the point?

Based on the current evidence, Dr. Staten says he would opt for the sauna. “It's been shown to have benefits across so many areas of health from dementia prevention to pain reduction in fibromyalgia.” Cold water immersion, in his view, hasn't earned the same credentials at this point. “I think the evidence for CWI, particularly in terms of long-term benefits, isn't really there yet.”

Of course, you don’t have to pick a side, and at the end of the day, the one that’s best for your health may be the one that you enjoy most and can regularly incorporate into your routine. “A sauna is always traditionally followed by a cold plunge so there is no reason you can't do both,” Dr. Staten adds. Heat first, then cold: an order that mirrors what saunas and cold plunges have done together for thousands of years, from the pit sauna and its bucket of icy water, to the modern spa with a plunge pool at your gym. After all, some things never change.

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