Diving into the science of cold plunges: Is it worth the icy dip?

Cold plunge videos are making the rounds all over social media now, and the activity seems to be quite the rage. Many find the act of jumping into nearly freezing water to be therapeutic.

When I asked friends and family who regularly cold plunge why they do it, some of the responses I got included “it helps me recenter myself, which usually relieves my anxiety” and “it helps me learn to be comfortable and control my breathing in the uncomfortable cold water.”

As a future osteopathic physician, I am intrigued to learn more about any drug-free practices that may improve our health, so I delved into reading the research on cold plunges.

Many of the reported claims about the health benefits of cold plunges focus on anti-inflammatory properties, boosting immunity and alleviating depression or anxiety. But are these health benefits real, and are there health risks to cold plunges as well? Below, I’ll break down the most commonly asked questions related to cold plunges, and I’ll discuss why they may or may not be the right fit for you.

What happens when your body temperature drops?

Cold plungers have different ideas of what a cold-water temperature is—some will say 60 to 50 degrees Fahrenheit is ideal, whereas others will say between 40 and 50 degrees Fahrenheit is the way to go. Studies have shown that many of the dangerous outcomes from cold water occur between 59 and 50 degrees Fahrenheit; therefore, for the purpose of this piece, we will define cold water as any temperature that is less than 59 degrees.

Hypothermia is a major concern related to plunging into icy waters. Hypothermia is clinically defined as having a core body temperature of less than 95 degrees Fahrenheit. According to the National Center for Cold Water Safety, it takes only 30 minutes for an average-sized adult to develop hypothermia in near-freezing water. However, it’s typically recommended to start plunging for only one minute or less.

Some of the dangers of cold water immersion can include cold shock, which is an autonomic nervous system response in which catecholamine hormones are released. This causes an increase in heart rate and respiratory rate, which in turn can lead plungers to quickly develop respiratory alkalosis (a disruption of your blood’s acid-base balance) from hyperventilation and subsequently lose consciousness.

An added danger to losing consciousness in the cold plunge is the risk of water aspiration and drowning. Drowning may also occur due to a nerve block resulting from nerve temperatures between 41 and 59 degrees Fahrenheit for one to 15 minutes.

This nerve block can cause paralysis, which inhibits people from being able to swim if this plunge is taking place in a large body of water or a pool.

With the autonomic response from cold-water immersion, your body will also try to protect its vital organs by increasing blood supply to the core. To do so, blood vessels to your extremities will constrict, which explains why your hands and feet get unproportionally cold and are the first to discolor. As this is taking place, you may also begin to shiver, which is a way for your body to attempt to generate heat. The amount of shivering positively correlates with dropping body temperature. So, if this is you in your cold plunge, take that as a sign to get out.

“Cold plunges, like other recovery tools, can be helpful when performed appropriately and when one knows the risks and benefits,” said Gene Tekmyster, DO. “For those looking to optimize recovery and performance, a well-balanced multimodal approach is best.”

Do cold plunges actually help with depression and anxiety?

There is a lack of scientific data to support the notion that cold plunges have positive effects on mood. However, according to patient-reported outcomes from questionnaires, there does seem to be a correlation between cold-water immersion and improved moods. According to research published by the journal Lifestyle Medicine, individuals who did cold plunges reported lowered cortisol levels, enhanced mood regulation and increased resilience to stress.

Another case report showed improvement in a patient with major depressive disorder who was unable to control symptoms with various medication trials. The patient was swimming in cold water weekly. Physical activity is often suggested as one route to treat major depressive disorder, so the exercise may have also played a role in this case.

How does the cold plunge modulate immune function?

There are many contrasting results on this topic. Some studies have shown that there are hematologic changes in cold water swimmers such as leukocytosis and increased levels of neutrophils, whereas other studies have shown no differences in these cell counts. One of these studies performed on athletic males who were intermittently immersed in cold water (57 degrees Fahrenheit) for an hour reported that immediately after immersion, there was minimal immune response in accordance to the plasma concentration of specific immune and anti-inflammatory markers. However, after successive immersions throughout the week and then over numerous weeks, there were increases in values such as monocytes and lymphocytes, as well as immune and anti-inflammatory receptors. Yet, levels of immunoglobulins, complement factors, leukocytes and neutrophils were not significantly different.

Another study separated people into groups of fast coolers and slow coolers depending on how quickly their body temperature dropped following immersion. In this experiment, it was found that there was a significant increase in leukocytes and neutrophils in the slow cooler group but not in the fast cooler group.

Overall, these results do suggest that repeated cold-water exposure does cause a noninfectious stress that can activate the immune system to some extent. These factors may be affected by different variables, such as how quickly your body warms and how long, as well as how frequently, you immerse yourself in cold water.

How do cold plunges affect the cardiovascular system?

A study of adapted winter swimmers specifically looked into lipoprotein, cholesterol, homocysteine and thyroid hormones, as well as antioxidant defense markers. The findings suggest a positive correlation between oxidative stress markers and cardioprotective mechanisms in cold-adapted individuals.

On the other hand, other studies have found increases in cardiac markers such as high sensitivity troponin, which may suggest adverse cardiovascular effects. This may be part of the link between strenuous/prolonged exercise and increased troponin elevation. So, whether these scenarios can indicate heart damage is still unclear. Another worry is the possibility of increased blood pressure that over the long term could result in cardiac hypertrophy. One study found that there were increased blood pressures in subjects as they waited undressed in the cold winter air, but neither the cold water immersion nor swimming caused further increases.

In addition, it was found that the pressure returned to the individuals’ baseline just four minutes after exposure.

What are the risks?

This fad does not come without serious risk. The National Center for Cold Water Safety states that sudden immersion into water temperatures between 50 to 60 degrees Fahrenheit can kill you within less than one minute. They explain that this is not necessarily due to hypothermia, but rather the nerve block that results in swimming failure.

In this article posted by the American Heart Association, Jorge Plutzky, MD, the director of preventive cardiology at Brigham and Women’s Hospital in Boston, advises patients with cardiac history to avoid indulging in these types of experiences. He explains that due to the lack of research as well as the varying results, it may be more of a risk to the individual. He also notes that beta blockers can make it more challenging for the body to adapt to cold water.

Knowing all this, would I recommend cold plunging?

I was originally extremely skeptical about the effects of cold plunging myself, which led me to dive into research. After much persuasion, I found myself taking part and surprisingly noticed great personal benefits.

I started by plunging in a small outdoor cylinder tub from one to three minutes about three times per day and then eventually worked up to five-minute plunges five times per day with an average temperature of about 60 degrees Fahrenheit.

Over a couple of weeks, I found some of my most productive days to be after plunging. When I sat down to study, I felt more focused on the tasks at hand and therefore was able to finish assignments or readings in a timelier manner.

I also felt so accomplished after learning to control my breath; it really felt like moments of mind over matter. When I first started cold plunging, the initial shock that led to hyperventilation made me quickly get out of the water. Over time, I was able to practice deep breathing instead of hyperventilating, which allowed me to stay in the water longer and be more comfortable with the discomfort of the extreme cold.

After researching, I do agree that the data can be conflicting and does not count for many of the variables that may affect study outcomes. There is a need for more controlled and updated experiments. Following my own experiences, I can better understand the excitement around cold plunging, as well as the possible positive effects that it can have on mental and physical health.

The research I found showed the best outcomes in those who acclimated slowly and repeatedly exposed themselves to cold water. In addition, due to the potential dangers, I do not think that everyone should be cold plunging, and I strongly believe that you should never do it alone. I would recommend consulting your doctor to make sure this is a safe activity for you, and take it slowly.

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