Sherpa people, an ethnic group of Nepalese Himalayas, demonstrate the ability of living at altitudes so high that normal humans would not be able to bear. How do they do this? New findings, published in Proceedings of the National Academy of Sciences, unveil the mystery.
Sherpas are ‘superhuman’ mountain climbers who can live at extremely high altitudes where oxygen supply is limited. In spite of this harsh environmental condition, the Sherpas can produce energy efficiently. New research conducted by a team of scientists from the University of Cambridge explains the biology behind; these findings also promise to help in the development of treatment methods for patients suffering from hypoxia (lack of oxygen).
High altitudes are characterised by low levels of oxygen—a condition that can be problematic to humans given that we need oxygen to produce energy. Oxygen scarcity causes the body to work harder to take in the essential gas so that an adequate amount reaches the brain and muscles. The human body tackles this problem by making more red blood cells (RBCs) which are known to transport blood (and thus oxygen) all around the body. While this is a marvellous adaptation, it also comes with a price: the blood might thicken with an increased number of RBCs, causing the flow thereof to decrease, creating a state where the risk of having clogged blood vessels is higher.
As such, different individuals show varying responses to high altitudes; the majority of mountain climbers will need an additional supply of oxygen when scaling Mount Everest while a few can go without. The latter include Sherpas—they can live up the highest mountain without apparently suffering from health conditions associated with low oxygen supply. To fully appreciate their superhuman ability, consider this: two Sherpas have successfully reached Everest’s peak 21 times. No big deal, huh.
The researchers, therefore, aimed at finding out the biological differences between Sherpas and people living at lower altitudes (lowlanders). They studied two groups of people climbing up to Everest Base Camp situated at an altitude of 5,300 m. It is to be noted that previous studies have shown clear genetic differences between Sherpas and lowlanders; mitochondrial DNA was different, and this is pertinent information because energy is produced in the cell compartment mitochondria. Other evidence suggests that the former’s ability evolved thousands of years ago: it is believed that the first humans resided on the Tibetan plateau 30,000 years ago, with permanent settlers emerging around 9,000 years back, implying that the superhuman ability might have appeared as a result of living in the extreme environment.
Furthermore, other studies indicate that Sherpas might have fewer RBCs, and more nitric oxide which dilates blood vessels, thereby ensuring a normal flow.
The University of Cambridge researchers conducted mitochondrial studies on the two groups of people. Blood and muscle biopsy samples of lowlanders were taken thrice: before and when they first reached Base Camp, and after two months spent there. This data was then compared with those from a group of Sherpas living in low-altitude regions.
The results show that the mitochondria of the Sherpas use oxygen more efficiently to produce energy. Furthermore, the Sherpas have lower levels of fat oxidation, a trait associated with a greater efficiency at generating energy.
Another interesting finding is that Sherpas display similar measurements for both low and high altitudes. This implies that they might have been born with the differences, and not evolved them through adapting to the higher altitude. On the other hand, lowlanders demonstrate a change after they spent two months at high altitude; this means that their bodies had to adapt to the environmental conditions.
An additional key difference entails the concentration of phosphocreatine which is an energy reserve that aids muscle contraction when ATP (main form of energy) is not available. Lowlanders had a great decrease after the two months while Sherpas had increases.
Lowlanders also had more free radicals which are created from a lack of oxygen, and can damage cells and tissues, while Sherpas have low levels of the molecules.
“Sherpas have spent thousands of years living at high altitudes, so it should be unsurprising that they have adapted to become more efficient at using oxygen and generating energy,” says Dr Andrew Murray from the University of Cambridge. “When those of us from lower-lying countries spend time at high altitude, our bodies adapt to some extent to become more ‘Sherpa-like’, but we are no match for their efficiency.”
These findings might also help people with hypoxia. Co-author Mike Grocott explains that understanding the ability of Sherpas can help researchers understand patients who are at higher risk of dying from lack of oxygen, and mount better treatment strategies.