What happens to your body on Mount Everest

“Human beings aren’t built to function at the cruising altitude of a 747,” the voice in the trailer for the film “Everest” warns. “Our bodies will be literally dying.”

It’s Rob Hall, played by actor Jason Clarke, as he prepares to lead an expedition up the world’s highest peak. The film, also starring Jake Gyllenhaal and Josh Brolin, is based on a 1996 climb, when eight people died during a blizzard. This particular journey is well known: Its horrifying details were chronicled in Jon Krakauer’s bestselling book, “Into Thin Air.”

But is that sensational Hollywood warning about bodies “literally dying” on Everest true? Those who’ve been there say yes.

With its peak at 29,029 feet, the mountain presents an intense challenge of icy temperatures and altitude where oxygen is limited. It’s not a hospitable place for any living thing, and people’s bodies begin to shut down. In 2016, four people have died on Everest in the span of four days, including a Sherpa, while two others have gone missing.

“Everest is a mountain of extremes,” said Jon Kedrowski, a geographer and climber. “At altitude, the body deteriorates on a certain level.”

Kedrowski summited Mount Everest in 2012, another brutal year on the mountain, when overcrowding combined with a dangerous weather pattern to strand climbers in the “death zone” below the summit. Ten people died.

Still, year after year, Everest draws those willing to study and train for the mountain’s rigors – and willing to take the risk.

Preparing for the climb

One of the first steps for anyone considering an Everest trek should be consulting with a physician to evaluate physical health. It’s also a way to discover any pre-existing conditions that might be amplified by high altitude, Kedrowski said.

If Kedrowski is leading a peak expedition, he screens his clients and designs training programs to help them prepare for the journey. When altitude is a consideration, cardio is the emphasis, rather than strength, Kedrowski said.

The elevation at Everest Base Camp is 17,590 feet, an altitude that decreases oxygen by about 50%. Before attempting a May summit, Kedrowski recommends arriving at base camp toward the beginning of April to acclimatize for a few weeks.

Previously, it was suggested that people arrive as early March, but 10 weeks, rather than five or six, can result in a loss of body mass, strength and endurance, Kedrowski said. This can make the climb more dangerous, or even impossible.

Well aware of the dangerous medical conditions and injuries that can happen on Everest, Dr. Luanne Freer founded the Everest Base Camp Medical Clinic in 2003. Physicians with mountaineering medical expertise and volunteers staff the medical tent during each climbing season.

On average, they treat 500 people between April 1 and the end of May for everything from high-altitude cough and acute mountain sickness to frostbite and high-altitude pulmonary or cerebral edema. They also treat multiple sprained or broken ankles due to the rocky terrain.

What can happen on Everest

High-altitude cough and acute mountain sickness are common ailments among Everest climbers. Mountain sickness results in headaches and shortness of breath, but can be managed by ascending no more than 1,000 feet a day, Kedrowski said.

No one is immune to high-altitude cough, Freer said. It may sound innocuous, but the cough results from breathing at an elevated rate in cold air at high altitude, which can dry out the lining of the lungs and cause it to crack. People have been known to break ribs with this cough, Freer said.

Climbers know to expect the shock of excessively cold temperatures and the possibility of frostbite as they ascend Everest, but they might not be prepared for the other extreme: heat. On Everest, the snow and ice act as a giant reflector for the sun’s glare. The potential for sunburn is particularly great in the Khumbu Icefall and the Western Cwm, near base camp, where daytime temperatures can reach 90 degrees Fahrenheit during climbing season, Kedrowski said.

Climbers also risk high-altitude pulmonary edema and high-altitude cerebral edema, known as HAPE and HACE, Freer said. They’re more likely higher up the mountain, in low-oxygen situations, when the body also reacts by creating pressure and excess fluid – in this case, on the lungs or brain.

Climbers can have a range of symptoms, from extreme fatigue and shallow breathing to dizziness and coughing up blood. The lack of oxygen to the brain, called hypoxia, can cause people to make poor, rash and sometimes deadly decisions in the confusing landscape.

The best and quickest treatment is for climbers to descend to a lower altitude, although many can’t do this on their own and must be helped or carried.

Eating to live

Food plays a major role in how someone’s body reacts to being on Everest. Digestion slows as climbers reach higher altitudes until the intestine becomes hypoxic and can’t send nutrients to the muscles, Freer said.

Kedrowski recommends small meals before ascending to different camps. Consuming too much food at once will send all of the blood toward the stomach to aid in digestion, which could redirect it from other imperative functions of the body at altitude.

At higher altitudes, the body begins craving more sugars and it becomes harder to digest protein. Kedrowski and his fellow climbers usually rely on plain noodles, canned vegetables and meats, rice and beans, soups and snacks like trail mix, chocolate, cookies and crackers.

Climbers rely on melting snow for water, which can also come with its own set of problems. As Everest’s popularity has increased, the number of climbers rises each year. This has created an accumulation of trash and human waste on the mountain. As a result, there are bacteria in some of the snow melt used by climbers, which can cause diarrhea.

Coming back to life

Freer and Kedrowski recommend following up with a physician after an Everest trek, especially if a climber encountered a medical issue. Many experience complications after frostbite and edemas can create scar tissue. Should a person choose to climb Everest again or tackle another similar feat, they’re more susceptible to those conditions in the future and could even die, Kedrowski said.

But he understands why people strive for the achievement. When he reached the summit amid nearly impossible conditions in 2012, Kedrowski felt accomplished to stand on top of the world – and relieved that he could descend and go home.

For those still dreaming of the ultimate height, Freer has some advice: “Be prepared for the ultimate stress test.”