Cryotherapy: What Is It, And Can We Use It To Improve Health And Longevity?

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This article concerns cryotherapy or cold therapy, but there are quite a few scientific terms that begin with ‘cryo’, so it helps to define them first in order to avoid confusion:

• Cryotherapy is the application of very low temperatures as a medical treatment.
• Cryogenics is the study of very low temperatures and their effects on materials.
• Cryopreservation is the preservation of cells, tissues and organs using very low temperatures.
• Cryonics is the cryopreservation of the recently deceased, in the hope that future technology will allow them to be revived.

There is a growing scientific interest in the therapeutic effects of low temperatures, with some suggestion that cold exposure could even help you live longer. In both warm-blooded and cold-blooded animals, whether in the wild or in the lab, colder conditions appear to be associated with longer lifespans. Cryotherapy takes this to the extreme, exposing the body to below-freezing temperatures for a short period of time with the intent to activate various beneficial responses within the body. What’s going on here? What happens when the body is exposed to (relative) extremes of low temperature, and is there any evidence that this can improve health and lifespan?

What Is Cryotherapy?

Cryotherapy can mean a few different things. The use of cold saunas, cryo-chambers or immersion in cold water to cool the whole body or a large part of it, cryosurgery (destroying diseased tissue using extreme cold) and even the simple application of an ice pack to a wound can all be considered to be forms of cryotherapy. In this article we’re mainly going to be focussing on partial and whole-body cryotherapy that expose the body to cold air.

When it comes to this type of cryotherapy, you will see references to cryo-chambers, cryo-saunas, and cold saunas – terms that aren’t always very well defined. What actually matters is how cold the chamber gets, how much of the body is exposed to the cold temperature, and how that temperature is achieved.

Cryochambers generally reach temperatures of -100°C or even lower. Some cryochambers are walk-in rooms in which dry air is cooled electrically, and may also be blown towards the user to accelerate cooling. Other cryochambers use nitrogen gas to cool the body. In these setups, the recipient’s head must remain outside of the chamber so that they don’t breathe too much of the nitrogen. While nitrogen is not toxic (about 80% of the air we breathe is nitrogen), it displaces the oxygen in the air, which could result in asphyxiation. Regardless of the method used, a standard cryochamber session doesn’t last very long – usually somewhere between 2 to 6 minutes.

What Happens When We Get Cold?

To understand how cryotherapy could be beneficial, we first have to understand what happens in the body when it is exposed to cold. In order to maintain a stable body temperature, blood supply is diverted away from the skin in order to limit the loss of heat to the air. Meanwhile, the body will begin to generate more of its own heat. The most noticeable way in which it does this is through shivering – rapid muscle contractions that occur specifically to produce ‘waste’ heat, which is beneficial in the context of cold temperatures. What’s more, the body’s metabolic rate – the total rate at which energy is expended – increases. Much of this increase in energy expenditure is down to brown and beige fat tissue, which is specialised for generating heat – you can read more about the different types of fat tissue here.

All of the above responses can occur when someone is exposed to cold temperatures, but the more extreme cooling during cryotherapy seems to have some additional effects. Evidence suggests that cryotherapy can reduce inflammation under some circumstances. Most of the evidence for this comes from athletes, who generally experience higher levels of inflammation as a result of intense exercise training, but there is also evidence from healthy non-athletes. These effects may be due in part to the release of adrenaline as part of the metabolic response to cold. Adrenaline generally suppresses inflammation. Other possible mechanisms include the constriction of blood vessels mentioned earlier, which reduces swelling and makes it harder for white blood cells to reach the extremities, as well as a decrease in metabolic rate in these tissues.

There’s also evidence that cryotherapy can increase the activity of antioxidants, even in non-athletes. Antioxidants are molecules that protect important components in the cell (such as DNA and proteins) from being damaged by reactive oxygen species, which are normal by-products of the cell’s metabolism.

Health benefits of cryotherapy

These biological effects of cryotherapy are all well and good, but do they actually translate to real health benefits? Evidence is emerging that they can, although some of this evidence remains quite conflicted.

Inflammation and Ageing:

Inflammation throughout the body is thought to be a key driver of age-related diseases, so any treatment that reduces inflammation could be valuable for improving human longevity. However, this will remain speculative until more research can be done. Currently not all studies are actually in agreement about cryotherapy’s anti-inflammatory benefits, with several reports unable to detect a link between cryotherapy and reduced inflammation. It’s also worth noting that the reduction in inflammatory molecules after 10 daily sessions of whole-body cryotherapy lasts about two weeks, according to a study in healthy men, suggesting you would need to receive the treatment on a semi-regular basis to see long-term benefits. Whether these effects translate to real health benefits needs further exploration, though there’s already some evidence that cryotherapy can help treat inflammatory diseases such as rheumatoid arthritis.

Pain and wound healing:

This is where most of the research concerning cryotherapy has been focussed due to the potential applications in high-level sports. The majority of studies in this area report that cryotherapy does have beneficial effects: research suggests that athletes experience reduced muscle pain, reduced muscle fatigue and faster recovery in the days following strenuous exercise if they receive whole body cryotherapy during the recovery period. On the other hand, a number of studies have failed to find any relationship between cryotherapy treatments and recovery from exercise.

Exercise-mimicking and weight loss:

These are perhaps the most enticing potential applications for cryotherapy for the average non-athlete. Studies suggest that cryotherapy can affect how the body handles fat, and can also mimic some of the beneficial effects of exercise. In healthy non-athletes, ten sessions of whole body cryotherapy were associated with a decrease in circulating triglycerides (the main fat storage molecule) by over a third, as well as a significant increase in ‘good’ HDL cholesterol.

Cryotherapy also appears to trigger the release of myokines, which are beneficial molecules released by muscle during exercise. This includes irisin, which has attracted interest as a potential ‘anti-obesity’ molecule. Irisin helps keep blood sugar low and encourages the formation of brown fat, a type of tissue that burns fat in order to generate heat. Because of this, researchers have studied whether cryotherapy can be used to aid weight loss and protect against diabetes.

The evidence here is somewhat mixed, and deserves further investigation. One study found that in 19 obese post-menopausal women, twenty 3-minute sessions of whole body cryotherapy were associated with a significant reduction in total body fat (about 0.5 kg). However, another study in with 45 overweight and obese men failed to find any beneficial effects of a similar cryotherapy course applied at the start and at the end of a 6-month exercise intervention. It is possible that the benefits of cryotherapy are dependent on the fitness of the recipient, as one study found that irisin levels increased following cryotherapy in low-fitness individuals, but actually decreased slightly in high-fitness individuals.

The Take Home Message:

Given what we understand about how the body responds to extremes of cold, cryotherapy seems like a promising treatment for improving health and longevity. However, evidence for real health benefits of cryotherapy is mixed. Studies lean in favour of cryotherapy being beneficial for people who exercise regularly, and it might also be helpful in obesity and some inflammatory diseases. It’s less certain whether cryotherapy benefits relatively healthy people.

One of the reasons the evidence is quite mixed could be that there’s no standard way of applying cryotherapy – the precise temperature, exposure time, cooling method, and the number of sessions are all factors that could impact the effectiveness of the treatment. Cryotherapy may affect different people in different ways – people with more fat tissue will retain heat better than a lean athlete.

It’s also worth noting that designing a cryotherapy trial with a proper placebo group (the group that receives a fake treatment) is difficult, and consequently many studies are not placebo-controlled or, worse yet, don’t include a control group at all. What’s more, the potential for a placebo effect is large because recipients are subject to a lot more attention from researchers than in a typical study (because they need to be monitored for safety). Many studies have other problems that could make their results unreliable. While there’s cause to be optimistic about the health benefits of cryotherapy, we need more, higher quality research to be able to say how effective it really is.