I love camping. Being around nature, away from the push and shove of the city is simply thrilling. You cook your own food, you walk a lot every day and you feel like a completely new person. Well in a way, you actually are a different person. A new study has found that just a few hours in the mountains can significantly change your bloodstream, and two weeks can have a long-lasting effect on your blood.

Photo by Jeremyfrimer.

It’s the first time researchers have thoroughly analyzed the blood of mountain hikers, and their findings contradict a century-old assumption. The assumption was that in high-altitude environments, humans start producing new red blood cells that are more capable of supplying oxygen to their muscles and organs than the average human’s blood.

“That’s been the story for 50 years,” Robert Roach, lead investigator and director of the Altitude Research Centre at the University of Colorado, told Richard A. Lovett at Science.

But experience tells us otherwise. While that may be true for populations spending their whole life in high-altitude environments, mountaineers and backpackers have long felt that this is simply not true. Basically, it takes at least a week for the body to start replacing the new blood cells, and people can feel the effects much faster than that – sometimes even overnight. So researchers knew that something wasn’t right.

In order to test their theory, they sent 21 healthy volunteers (12 males and nine females, 19 to 23 years old) to Bolivia, at an altitude of 5,260 metres (17,257 feet). At that altitude, the atmosphere holds 53% as much oxygen as the air at sea level, making it harder to breathe – and to exercise. But the body can adapt.

The volunteers were tasked with a 3.2-km (2-mile) hike, after which they descended to 1,525 metres for a seven day rest period. After this, they were asked to go up again and attempt the same hike. Their blood was monitored for the entire period. The initial results showed that the second time, the hike was much easier. But blood samples showed an intriguing result as well: the body wasn’t producing new blood cells, it was changing the one it already had. The changes were far more complex than they had anticipated.

“We provide for the first time supportive evidence of red blood cell metabolic adaptations that ensue within hours from exposure to high altitude hypoxia,” the team concludes.

This is exciting for several reasons. First of all, it means that even if you’re not born with a high-altitude genetic variation, you can still easily adapt to the environment. Second of all, it means that our bodies are much better prepared in dealing with these situations than we thought. It could also have an unexpected significance, enabling us to better treat some wounds.

“Low oxygen is also a problem when trauma – from car accidents to gunshot wounds – causes blood loss,” says Lovett. “Finding ways to kick the blood’s oxygen-carrying capacity into high gear in such an emergency … could save lives in both the civilian sector and on the battlefield.”

So get that old tent out from the closet and put on your trekking boots – it’s time to hit the mountains!