What Really Happens to our Bodies at High Altitude? By Lauren Berengo

Lauren Berengo

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Whether you’re flying, hiking in the mountains or an avid skier, most of us have experienced some sort of unexplained discomfort at High Altitudes. You may have difficulty sleeping, feel a little more bloated or gassy than usual or experience dry skin and chapped lips – your concerns are not unwarranted as there are many changes our bodies experience when adapting to high altitudes. 

OXYGEN
 
High Altitude (HA) is defined as elevation of 8,000 to 12,000ft, although symptoms associated with HA can be experienced from as little as 1000-2000ft elevation -- especially if the body is accustomed to living and breathing at sea level. For every 1000ft you ascend, there is a 3% loss of oxygen, causing an increase in heart rate, respiratory rate and fluid loss within minutes of ascending. Over a period of time, the body begins to produce more red blood cells and capillaries to transport oxygen more efficiently and help minimize the effects of hypoxia (deficiency in the amount of oxygen reaching the tissues).  
 
Hypoxic conditions can affect cognition and motor skills in a variety of ways:

NUTRITION & DEHYDRATION 
 
Regardless of whether you are incredibly active (skiing/hiking) or just hanging out at HA, there are increased nutritional and hydration requirements. Our bodies are using a lot of energy just to help us breathe and keep us warm, increasing our total energy expenditure quite dramatically and depleting our glycogen stores. This not only calls for an increase in total calorie consumption (it may be double if you are vigorously active), but specifically an increase in carbohydrate consumption. 

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CARBS ARE YOUR BEST FRIEND
 
Carbs are the most efficiently metabolized macronutrient at HA as they require 8 – 10% less oxygen to metabolize than protein or fat. In fact, a study of the most successful Mt. Everest climbers showed that the optimal balance of macronutrients was 58% carbohydrates, 30% fat and 12% protein. These requirements may vary from individual to individual so it is important to consult your doctor or dietician before making any changes to your diet. There are also symptoms associated with low blood glucose levels which include becoming confused and irritable. 

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WHAT ELSE IS GOING ON?
 
It is common to experience headaches and a decrease in appetite as blood flow is redirected away from the digestive system and towards the brain, heart and lungs. Additionally, changes in atmospheric pressure can also cause gas, bloating or other intestinal discomfort. Low oxygen levels also increase the body’s sensitivity to alcohol and caffeine due to dehydration – so it may be best to skip boozing up after hitting the slopes. Keep in mind that our body’s alcohol tolerance is also significantly decreased, so it is best to halve your intake or monitor how you are feeling regularly. Signs of dehydration can sometimes be suppressed or masked by the cold, but it is extremely important to sip water throughout the day (1L every 3hrs) and keep a bottle of water handy at bedtime. (You will most likely be awake throughout the night). 

​SLEEP
 
As previously discussed, hypoxia can have an effect on a range of bodily functions including our sleep. Hypoxia can reduce overall sleep time and efficiency, slow-wave sleep and REM sleep, not to mention it causes our bodies to wake up continuously throughout the night to make sure we are still breathing. 
 
High altitude period breathing is a pattern of breathing we experience during our nights in the mountains and on flights. It is characterized by periods of deep breathing (3-5 breaths) followed by shallow breaths or a complete pause in breathing (apnoea). According to a study performed by the American Academy of Sleep Medicine, supplementing your sleep with melatonin has shown to significantly improve the quality, length and onset of sleep. In turn this increased mean reaction times significantly during activities the following day. 

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​By understanding how your body responds and adapts to high altitude conditions, you are able to better prepare for your next ski trip or long-haul flight. Our bodies have an amazing ability to adapt, so make sure you are loaded up on carbs, hydrated and get as much rest as possible! 
 

References
 Bian, S. Z., Zhang, L., Jin, J., Zhang, J. H., Li, Q. N., Yu, J., … Huang, L. (2019). The onset of sleep disturbances and their associations with anxiety after acute high-altitude exposure at 3700 m. Translational psychiatry, 9(1), 175. doi:10.1038/s41398-019-0510-x
Celmer, L. (2017). Melatonin may improve sleep and cognition at high altitudes. American Academy of Sleep Medicine. 
 Karl, J. P., Cole, R. E., Berryman, C. E., Finlayson, G., Radcliffe, P. N., Kominsky, M. T., … Pasiakos, S. M. (2018). Appetite Suppression and Altered Food Preferences Coincide with Changes in Appetite-Mediating Hormones During Energy Deficit at High Altitude, But Are Not Affected by Protein Intake. High altitude medicine & biology, 19(2), 156–169. doi:10.1089/ham.2017.0155
 Kechikan, D. (2011). Optimizing nutrition for performance at altitude. Journal of Special Operations Medicine, 11, 12-17.
  Windsor, J. S., & Rodway, G. W. (2007). Heights and haematology: the story of haemoglobin at altitude. Postgraduate medical journal, 83(977), 148–151. doi:10.1136/pgmj.2006.049734