The Science of Cold Therapy and the Pros and Cons of Cold Exposure
An increasingly popular trend in the wellness world, cold therapy involves using low temperatures to address various conditions, relieve pain, or boost mental resilience. With potential benefits ranging from increased lifespan and improved muscle recovery to brown fat activation and blood sugar regulation, cold therapy is a modern take on a centuries-old approach to healing.
What Is Cold Therapy?
There are several approaches to using cold temperatures to reduce inflammation, alleviate pain, and promote healing, including ice baths, cold plunges, cryotherapy chambers, cold showers, and even ice packs.
Ice baths, cold showers, and cold plunges utilize the same method—immersing the body or specific body parts in cold water to reduce muscle soreness and inflammation, speed up recovery after exercise, or boost alertness. The temperatures here are typically 45°F to 60°F.
Cryotherapy chambers are a newer kid on the block, with specialized chambers that expose people to extremely cold temperatures (as low as -150°F to -240°F) for just a few minutes.
Ice packs are a well-known way to reduce pain and inflammation in a small area, typically after injury or exercise. The cold packs constrict blood vessels, reduce swelling, and numb the area to alleviate pain.
Lastly, some athletes use cold compression therapy, a device that delivers cold temperatures and pressure to an injured area to reduce swelling and pain.
6 Health Benefits of Cold Exposure
1. Increases Longevity in Animals
Although research has not been done in humans, some studies with worms, flies, rodents, and fish show that cold exposure can increase lifespan.
In research with the short-lived fish Nothobranchius furzeri, lowering their water temperature from 77°F to 71°F increased both the median and maximum lifespan and prevented the typical onset of age-related motor and learning dysfunction.
The increase in longevity from cold exposure could be due to a process called hormesis—when small doses of a stressor trigger beneficial adaptive responses that improve resilience. Cold therapy, exercise, and calorie restriction are all examples of hormetic stressors.
Another theory is that cold exposure increases lifespan by the “rate of living” hypothesis, which suggests that low temperatures slow the rate of metabolic processes, leading to fewer harmful metabolic byproducts like reactive oxygen species that cause oxidative stress. Plus, cold exposure has been shown to activate specific genes and pathways associated with increased lifespan.
2. Increases Brown Fat
Brown fat, also known as brown adipose tissue (BAT), contains energy-producing mitochondria, which give it its copper-brown color. Brown fat cells are comprised of many smaller droplets, and the mitochondria can burn up some droplets to create heat.
The thermogenic properties of brown fat increase energy expenditure, which can support a healthy body weight. While the amount of calorie-burning provided by brown adipose tissue varies from person to person, one study estimated that fully stimulated BAT could lead to an additional 100 calories per day of energy expended. At the same time, other researchers have suggested that increasing brown fat could boost energy expenditure by up to 20%.
Brown fat also reduces inflammation, supports healthy glucose metabolism, and induces post-meal thermogenesis, which helps with satiety and feeling full after we eat.
Exposure to cold temperatures is one of the best ways to activate brown fat (or trigger the transformation from unhealthy white fat to healthy brown adipose tissue). This is due to brown fat’s thermogenic effects, as cold temperatures activate the fatty tissue to burn energy in a process known as non-shivering thermogenesis.
Cold exposure can be performed by turning down the thermostat, taking a walk outside in the winter, taking cold showers or plunges, or using cryotherapy. The temperature range most often studied is not even that low—just 64-66°F. Although the most benefits have been seen with two hours of cold exposure daily, even shorter amounts can be beneficial. Research shows that ten days of a cold acclimation protocol increases brown adipose tissue activity and thermogenesis.
3. Improves Muscle Recovery and Reduces Soreness
Whether you’re a serious athlete or simply sore from a beginner’s gym session, cold therapy can help to improve muscle recovery and reduce post-exercise soreness. Delayed onset muscle soreness (DOMS) is a typical result of post-exercise microtears, and research shows that cold water immersion can mitigate it or speed up recovery time.
Cold exposure can reduce muscle inflammation after exercise by constricting blood vessels and preventing swelling. It also reduces the excessive breakdown of muscle tissue and enhances recovery by promoting the repair of muscle fibers. While all exercise causes microtears in muscles—back to that concept of hormetic stressors—cold exposure can mitigate these microtears and lead to quicker recovery.
In a meta-analysis including 17 small trials, some studies indicated that cold water immersion reduced muscle soreness for up to four days after exercise and improved recovery and fatigue immediately afterward. However, another review of four studies found insufficient evidence that whole-body cryotherapy reduced self-reported muscle soreness or improved recovery after exercise.
4. Strengthens Immunity
Cold therapy may support the immune system by modulating markers of inflammatory pathways. It’s thought that cold temperatures also strengthen immunity by stimulating the circulatory system and increasing blood flow, which may encourage the production of white blood cells.
One older study found that six weeks of cold water immersion (57°F for one hour, three times per week) caused beneficial changes to immune markers, including activation of T and B cells and monocytes.
5. Regulates Blood Sugar
Research has found that acute and repeated exposure to cold temperatures benefits insulin sensitivity and blood sugar regulation—two essential components of metabolic health. It’s thought that cold therapy enhances the body’s response to insulin, meaning that glucose is cleared from the blood faster and utilized by tissues. These metabolic benefits may be due to shivering skeletal muscles, which uptake glucose in significant amounts.
Another potential reason is that cold exposure increases adiponectin levels—a protein that regulates blood glucose. Low adiponectin levels are commonly seen in cases of insulin resistance or other blood sugar regulation disorders.
A small study with healthy men showed that adiponectin levels increased by 70% after cold exposure while drinking a high-carbohydrate beverage, suggesting better glucose control. In animal research, rats exposed to cold temperatures had increased glucose uptake into their tissues (indicating lower glucose in the blood).
6. Boosts Mental Alertness
Although we don’t have research on this one, plenty of anecdotes report that cold plunging or immersion increases alertness, mental clarity, and mood for an acute amount of time. This may be because cold therapy activates the sympathetic nervous system and increases the production of endorphins and the neurotransmitter norepinephrine.
Norepinephrine is a vital component of the body’s fight-or-flight response. While we certainly don’t want this system activated at all times, a short-term increase (like when the body gets shocked from cold exposure) can acutely increase alertness, attention, and concentration abilities.
Downsides of Cold Therapy
While there are plenty of potential benefits of cold therapy, there are also some serious side effects that you should be aware of before jumping into that Arctic-temperature lake.
One serious risk associated with cold exposure is hypothermia—when a person's core body temperature drops below 95°F. If the cold immersion is done in a large body of water (like a cold lake or ocean), the risk of impaired respiration and drowning is high if hypothermia occurs.
Cold therapy can also cause a cold shock response—when someone enters the cold water and has rapid cooling of the skin, a gasp response, and uncontrollable hyperventilation. If unsupervised, a cold shock response can cause drowning.
Another risk is heart issues, as cold water immersion causes instant increases in heart rate and blood pressure. These rapid changes significantly increase the risk of serious cardiovascular events or irregular heartbeats. For these reasons, you should never attempt cold water swimming alone.
Frostbite is another potential complication, which is more likely to occur in long cold exposure or cryotherapy, where the body is exposed to extremely low temperatures.
Lastly, a less severe side effect is that cold therapy may blunt muscle hypertrophy after working out—meaning you won’t be as sore, but you won’t get the same muscle gains from your workout. In a systematic review of eight studies, cold water immersion was found to have a negative effect on resistance training but did not affect the outcomes of aerobic exercise.
Key Takeaways:
Cold immersion therapies have been utilized for centuries, and recent research on the benefits of cold exposure is rapidly growing. Whether through ice baths, cold showers, swimming in a lake, or using a cryotherapy chamber, exposure to cold temperatures has been found to increase brown fat activity, improve metabolic health and blood sugar regulation, improve muscle recovery and soreness, and support immune cell markers.
In animals, cold exposure has shown promise for extending lifespan, and people anecdotally report the mental and cognitive benefits of cold therapy. However, there are some risks to be aware of, and people with heart conditions should consult a healthcare professional before practicing cold water immersion.
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