What Happens To You When You Fly?

How to Maintain Wellbeing at Thirty Thousand Feet
Untitled-1_0009_13. Jetlag

After more than a year of coronavirus-imposed travel restrictions, many of us are now tentatively considering the prospect of hopping back onboard the good-old metal flying machines and catapulting ourselves into the ether with the aim of landing somewhere hot and sunny, with great food, no one we recognise, and the hope that we get stranded there indefinitely. However, aeroplanes have had some pretty bad press since the start of the covid saga, gaining a strong reputation as highly reliable disease incubators, methodically circulating everybody’s germs firmly throughout all the lungs existing within the capsule. But are aeroplanes really the super spreaders we now know them to be? What other ways can flying affect our health? And, most importantly, what can we do about it?

On average, commercial passenger planes cruise at between 30,000 and 42,000 feet, which is a mighty 5 to 7 miles up in the air. For reference, the tip of Mount Everest sits at 29,029 feet. There are many reasons why planes fly so high, from avoiding turbulence and collisions with birds to reducing air resistance and fuel consumption. However, with this height comes changes in temperature, pressure, oxygen and humidity, which can have some pretty bizarre effects on the human body.

Here are 8 ways that flying can impact our wellbeing and what to do about it:

1) Germs

Aeroplanes aren’t as bad for spreading disease as you might first imagine. For example, it has been found that the risk of contracting COVID-19 during air travel is lower than contracting it from an office, classroom, supermarket or train(1). The air provided to passengers in the cabin is a mixture of air from outside the aircraft and recirculated air that is passed through HEPA filters. HEPA filters are designed to remove contagious and harmful particles from the air. Using air from outside the plane means that the air in the cabin changes completely every two to three minutes. The airflow enters from the ceiling and flows down to outlets at the floor level. This airflow is designed to flow from side to side rather than forwards and backwards to reduce any spreading of air-borne particles between rows. However, not all aircraft use HEPA filters and many other factors can also affect airflow within the plane. An example of where airflow design was not sufficient to reduce the spread of disease was seen in the SARS outbreak on Air China flight 112, which was only 3 hours long, and involved the infection of people as far as seven rows away from the infectious person(2).

There are several things that air passengers can do to reduce their chances of catching or spreading infections. These include wearing a mask, not travelling if unwell, and limiting carry-on baggage to reduce congestion when boarding and disembarking the flight. With regards to the overhead air nozzle, you should consider pointing it straight at your head and keeping it on full. Wash or sanitize hands frequently and avoid touching your face.

2) Cosmic radiation

Cosmic rays are poorly understood atom fragments that plummet through the earth’s atmosphere from outside the solar system. When us humans are flying up high in the thinner air, there are less gas molecules to deflect the cosmic rays and so we are more exposed to them than down on earth where the air is “thicker.” It is estimated that a return transatlantic flight would expose a human to 0.1 millisieverts(3) (mSv) of radiation, which, for comparison, is equivalent to 5 chest X-rays (0.02 mSV each), but is far less than the average amount of background radiation a person is exposed to on the ground each year (2.2 mSv), especially here in Cornwall where we are perched on a bed of radioactive underground rocks. Many people associate these sources of high energy or ionising radiation with cancer, but scientists consider that 100 mSv is the minimum amount of exposure a person would need to experience per year to have an increased risk of cancer. A one-off dose of 1000 mSV (1 SV)(4) would also likely have severely detrimental effects on a person’s health.

There isn’t really anything we can do to reduce our cosmic radiation exposure when flying, but considering the benefits we are most likely gaining from flying abroad in term of our wellness, it is easy to see that this additional exposure to radiation is quite insignificant.

3) Jet lag

There are many aspects to flying that mess with our sleep. Trips involving flights often require nauseously early starts and lengthy stopovers in uncomfortable airport lounges. What’s more, there’s also the added complication of jet lag, which generally occurs when you cross multiple time zones, and is characterised by sleep disturbance and daytime fatigue(5). Jet lag is caused by the disruption of the body clock which tunes your sleep-wake cycles to the light and dark phases of the day. Jet lag is thought to be worse as the number of time zones crossed increases, and is worse on eastward flights than westward flights, although the reasons for this are not totally clear.

There are many suggestions for how to reduce the detrimental effects of jet lag before, during and after your flight. For example, before your flight, you can ensure that you’ve stayed well hydrated(6) and rested, so that you do not already have a sleep debt before flying, or you can even start shifting your sleep patterns in the run up to your flight, forward or backwards, in line with your destination. When you get on the flight itself, you should start eating and sleeping as if you were in the time zone of your destination, and again maintain that all-important hydration, avoiding caffeine and alcohol. On arrival, try sticking to the new time zone, avoid napping and consider using caffeine or light therapy (exposure to bright light in the morning of your destination) to shift you into the new routine.

Try our Lights Out #07 formula to help you rest well before and after your flight.

4) Ear pops and hearing loss

We know that when we fly, the pressure of the cabin is carefully controlled because large pressure changes can be catastrophic for the human body. But why is it then that our ears still “pop” during a flight(7)? At sea-level, the pressure is 14.7 psi, while at 36,000 ft, a height at which many aircraft fly, the pressure is 3.3 psi. Within the pressurized aircraft cabin however, the pressure is not maintained at the sea-level pressure we humans are used to (14.7 psi), but is reduced to around 11.3 psi, which is roughly the pressure you would experience at 7000 ft with no pressurization. This reduction in cabin pressure is enforced to prevent any damage to the plane (or need for thicker and stronger aircraft walls) that can be caused by too big a difference in pressure between the inside and outside of the aircraft(8).

So, when the cabin pressure is reduced from 14.7 psi to 11 or 12 psi when we ascend, the pressure in our inner ear becomes much higher than the pressure outside, and the reverse occurs during descent. This difference in pressure affects and stretches the ear drum (tympanic membrane), which can then lead to eardrum pain and perforation, vertigo and hearing loss. Approximately 10% of adults and 22% of children are thought to experience changes to their eardrum after a flight, but perforation is rare, and symptoms usually go away on their own(9).

There are, however, several methods that flyers can employ to combat ear pain. The first is to repeatedly swallow and yawn. To help with this you should stay hydrated, chew gum and suck sweets to help produce enough saliva for swallowing. Swallowing helps to push air into the Eustachian tube, which feeds air into the middle ear, helping to equalize the ear pressure. Another, more forceful method is known as the Valsalva manoeuvre. Take a breath before shutting your mouth and pinching your nose shut. Then, gently try to force the air out until your ears pop. This manoeuvre also helps to open the Eustachian tubes. An alternative method, which is preferable if you are experiencing congestion, is the Toynbee manoeuvre, which also involves closing the nose and mouse but instead of pushing the air, swallow repeatedly.

5) Taste buds

It’s not just our imagination, food really does taste different at 35,000 ft, which helps to explain some of those more unusual menu options you can find when travelling the skies. Many airlines employ special recipes to try to compensate for the fact that our ability to taste saltiness and sweetness (the two most important tastes, of course!) is reduced by around 30% when flying. A study(10) performed in Fraunhofer Institute in Germany, found that more salt, sugar and herbs were needed during flight to make meals taste similar to ground conditions. Meanwhile, sour ingredients had to be reduced. Light, fresh flavours decreased during simulated flight while intense flavours persisted. Furthermore, the umami taste, which is characterised by foods like mushroom, seaweed and tomato, is thought to be enhanced during flight.

There are several reasons why our tastes change during flight. These include the low temperature, lack of humidity, the lower blood oxygen levels (caused by the lower pressure), high stress levels and even the noise of the flight(11).

There’s not a lot we can do as mere passengers to avoid the change of taste we will experience. We simply have to hope that the airline provides us with food with intense flavours and some extra salt and sugar. If you are taking snacks with you, consider good quality protein snacks such as unsalted nuts, olives and easily digestible cheese, which should sustain us and provide flavour onboard. An extra precaution would be to ensure that you never board a flight hungry, but don’t eat right before your flight or might be at risk of…

6) Bloating and constipation

On the note of food, some of us may not feel particularly hungry as we coast above the clouds. In the same way that the reduction in pressure we experience as we ascend affects the air trapped in our ears, it also affects the gases trapped in our bellies. As pressure decreases, gases expand, and so you may often find that you experience the phenomenon of “jet belly,” feeling particularly and uncomfortably bloated during, and even after your flight.
Another side effect of flying, and other types of travel, is constipation. Sitting still for long periods of time and changes to your diet that naturally occur from your change in schedule mean that your digestive system just will not work as it usually does.

The best ways to fight jet belly and other bowel issues are to eat regular healthy snacks on board, make sure you get up and move around during the flight, and keep hydrated. One of the best snacks for preventing constipation without generating tonnes of bloat-worthy gas, is kiwifruit(12).

7) Skin dryness

The lack of humidity on board aircraft is responsible for a plethora of negativity with regards to our wellbeing during flight. This lack of humidity in airplane cabins is really quite staggering, at often below 20%(13), which is less than the Sahara Desert (average humidity of 25%) and far less than the Environmental Protection Agency (EPA) recommends for houses (30% to 50%). This low humidity can make your nose, throat and skin feel particularly dry.

The best way to combat this dryness is to stay hydrated, use carrier oils, moisturiser and even use eye drops if you feel the need.

8) DVT and swollen feet

One of the most famous health issues related to flying is deep vein thrombosis or DVT, with relatives often advising you to take morbidly unfashionable compression stockings with you on your next long-haul flight. DVT is a blood clot that forms in a vein, usually in the leg, that is mainly caused when the blood flow in the leg is restricted in some way. Such blood clots can be incredibly dangerous and even fatal if they make their way to the lungs (pulmonary embolism).

However, there has been some debate around the connection between DVT and flying. There is evidence that passengers on long haul flights are three times more likely to develop DVT than the general population, with flights longer than 8 hours being most risky(14). There is a similar risk for people staying in hospital after surgery. However, this DVT risk is not unique to flying-based transport; anyone travelling for more than 4 hours, whether by car or train or plane, has a risk of DVT.

DVT and the less dangerous swelling of the feet and lower legs that may occur during flight, happen due to the lack of movement and position of the legs over long periods of time. Besides wearing beastly tight compression stockings, the best ways to reduce your risk of DVT are to move around the plane regularly (e.g., once an hour), drink plenty of water (to maintain blood volume), avoid crossing your legs and wear loose clothes(15).

Overall, we can see that many of the health issues that we are likely to face during a flight can be addressed by drinking plenty of water. So, when you next hop on that plane to get that ultimate feeling of landing on the runway of a new destination, remember to prioritise your wellness and pack your reusable water bottle!

  1. Risk of COVID-19 During Air Travel | Patient Information | JAMA | JAMA Network
  2. Infectious Risks of Air Travel | Microbiology Spectrum (asm.org)
  3. Radiation exposure from medical scans | Nuffield Health
  4. Factbox: How much radiation is dangerous? | Reuters
  5. Jet lag. – Abstract – Europe PMC
  6. Air Travel: Effects of Sleep Deprivation and Jet Lag – ScienceDirect
  7. The Effect of Flying and Low Humidity on the Admittance of the Tympanic Membrane and Middle Ear System (nih.gov)
  8. Aircraft Pressurization Beginner’s Guide – AeroSavvy
  9. Middle-ear pain and trauma during air travel (nih.gov)
  10. Odor and taste perception at normal and low atmospheric pressure in a simulated aircraft cabin | SpringerLink
  11. Airplane noise and the taste of umami | Flavour | Full Text (biomedcentral.com)
  12. Increasing dietary fiber intake in terms of kiwifruit improves constipation in Chinese patients (nih.gov)
  13. Air travel advice (who.int)
  14. Deep vein thrombosis and air travel: risk management in 2015 – Servier – PhlebolymphologyServier – Phlebolymphology
  15. Blood Clots and Travel: What You Need to Know | CDC
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