The effects of flying on your body


Sleeping on a plane

Most people will be aware of the effects of jet lag, and might know that with alcohol, one in the air is three on the ground. Deep vein thrombosis has received a lot of press recently. There are however some other medical topics that are less well known. This article seeks to educate the reader to allow them to take informed decisions about flying, the risk and how to take preventative measures.

Factors to look out for

UV light

Pilots and flight crews are twice as likely as the general population to develop skin cancer. (Melanoma)

Although plane windows are designed to resist UV-B radiation, an average of 54% UV-A radiation was found to come through. In the cockpit during a two-hour morning flight, intensities of UV-A reached almost 10 times the recommended exposure limit. People who fly regularly are advised to close the window blinds as much as possible, or to wear sunscreen with UV-A protection and get regular health checks by a dermatologist and/or health screening. Eating cooked tomatoes will provide your recommended dose of lycopene, an antioxidant that helps to protect the skin from UV rays.

Dried air

Dried air contributes to increased incidence of upper respiratory infection. The natural human defense system against colds consists of a layer of thin mucus that traps viruses and bacteria and moves them from the nose and throat to destruction by acids in the stomach. When the air is dry, the mucus becomes too thick to be effectively moved from the nose and throat to the stomach. This leaves more viruses and bacteria to cause upper respiratory tract infections.

Cold transmission

The risk of catching a cold increases between 15 and 113 times the normal level on the ground, with the variation mainly due to the time of year and the population studied. The increase in cold risk has been attributed to lower perfusion of outside air in the aircraft as well as high proximity to other passengers. Aircraft with full passenger loads provide the lowest volume of air per person of any public space. Drier air in aircraft can also increase the incidence of respiratory tract infections.


The effect of alcohol at altitude is heightened due to the pressure in the cabin being less than the atmospheric pressure on the ground. Alcohol dehydrates you. Always drink double the quantity of water to alcoholic drinks consumed.


Caffeine dehydrates you. Drink twice the volume of water as compared to any caffeinated drinks to counter this.

Fizzy drinks

Fizzy drinks are acidic and de-hydrate you. Avoid on flights and if you do drink them, drink twice the volume of water to compensate.


Water is the key of life. Water transports nutrients and oxygen into cells, assists with metabolism, detoxifies, protects vital organs and helps them to absorb nutrients, regulates body temperature, protects and moisturizes joints, to mention but a few of its many benefits. Lack of water compromises

every vital function of the body. A mere 2% drop in body water can trigger short-term memory issues, trouble with basic brain functions and difficulty in focusing. This is particularly important in a fatiguing drying environment such as on a plane.

  • How much & when 1.5 to 2 litres per day
  • How and when to take it? Sipped throughout the day
  • How long for? Ongoing

Foods to choose / foods to avoid

A healthy body strives for balance and the right pH in the blood is essential for its vital functions. All foods and drinks are either alkaline-forming or acid-forming after they are digested. Consuming too much of one and not enough of the other, will eventually throw your body out of balance.

Be aware of the acid and alkalising quality of foods in the body and try to combine them in ways that will benefit your overall health. A general guiding rule is that the more natural the state of the food, the higher the alkaline content.

The following list provides a general guideline of foods classified according to their effect on the pH of the body:

Highly Acidic

Wheat, gluten-flour bread, gluten-flour pasta, breakfast cereals, chickpeas, dried peas, animal protein, dairy (eggs, cheese, milk, butter, yoghurt, ghee, peanut butter), alcohol, beer, black tea, coffee, cola drinks, sweetened fruit juice, soda water, sugar, artificial sweeteners, jam, jelly, mustard.

Mildly acidic

Wholemeal bread, wholemeal pasta, amaranth, brown rice, buckwheat, hemp protein, lentils, oats, quinoa, rice, rye, spelt, wild rice, freshwater wild fish, ocean fish, oysters, liver, organ meats, borage oil, evening primrose oil, flax seed oil, marine lipids, sunflower oil, grapeseed oil, avocado oil, flax oil/ udo’s oil, nuts, seeds, fresh natural juice, ketchup, mayonnaise.


The vast majority of vegetables, barley, millet, beans and legumes, lima bean, soya beans/tofu, butter beans, white haricot beans, mung beans, distilled water, almond milk, rice milk, goat’s milk, soya milk, fresh coconut water, apple cider vinegar, soy lecithin, most herbs and spices.

Highly Alkaline

The vast majority of fruit, sprouts (alfalfa, chia seed, etc.), grasses (alfalfa, wheatgrass, etc.), almonds, coconut oil, olive oil, alkaline water (pH 9.5), fresh vegetable drinks, lemon water, fresh herbs, raw honey, Himalayan salts, cayenne pepper.


Sitting immobile for long periods on long haul flights can increase the risk blood clots and deep vein thrombosis (DVT). Flying at altitude exacerbates the risk as compared to sitting for long periods on the ground. This may be caused by lower oxygen at higher altitudes while flying. In addition to this, dried air in the cabin and lower cabin pressure at high altitudes contribute to dehydration and concentrating of the blood. Increased blood viscosity can contribute to blood clots. This effect is worsened by the dehydrating effects of alcohol and inadequate consumption of fluids. Frequent flyers have been found to be 3.65 times more likely to develop DVT. The risk of developing a clot was found to be 1 in 5,944 flights. If more than one flight was taken within a four-week window, the risk of clotting was slightly increased. Hydration and mobility are key to preventing thrombosis, in addition supplements such as milk thistle can help to thin the blood and prevent clots along side pharmaceuticals such as aspirin.

Lack of oxygen at altitude

At altitude the amount of oxygen available for you to breathe is reduced. This can affect oxygen distribution to the heart, brain and other tissues where it is needed for adequate function. You may be at risk of suboptimal organ function if you suffer from heart, lung or circulation problems.


As aircraft pressure decreases upon take off the air in the lungs needs to escape. If this cannot occur due to an acute asthma attack that closes the airway between the mouth/nose and the lungs, the air has nowhere to go and can cause a bubble which in extreme cases can puncture the lung. Asthmatics are advised to ensure they are free of symptoms before flying and use their medications more freely before travel.

Illness or ear infections

As aircraft pressure decreases upon take off the air in the middle ear needs to escape, this occurs through the Eustachian tube that connects your ear to your sinuses. Air travels more easily out through this tube than back in and when landing air needs to get back into the middle ear and this often requires the Valsalva maneuver (breathing out while holding the nose and closing the mouth to ‘pop the ears’). When suffering from a cold the eustatian tube may be blocked and pressure equalisation may be difficult, it is therefore not advisable to fly with a sinus or inner ear infection.

Jet Lag Prevention and Treatment

Symptoms of jet lag include disturbed sleep, increased fatigue, loss of concentration, and increased irritability during the new daytime, and yet difficulties in initiating and maintaining sleep at night. Generally, the intensity of symptoms varies in relation to the number of time zones crossed and the direction of travel. (Travelling east is worse than west). Jet lag is caused by the de-synchronisation between various body rhythms and environmental rhythms. It takes several days for the external factors to shift the phase of the body clock from the original time zone to your destination time zone. Behavioural changes to your regime in the few days before your flight and the few days after arrival can help alleviate jet lag. The most important cue is light:

  • For a westward flight, to stay awake while it is daylight at the destination and to try to sleep when it gets dark at the destination.
  • For an eastward flight, at your destination it is advisable to be awake but avoid bright light in the morning, and to be outdoors as much as possible in the afternoon
  • Taking melatonin is another option, this is a hormone that stimulates the body’s sleep cycle and can help to adjust your body clock faster, 2-5 mg melatonin taken at bedtime after arrival is effective at reducing jet lag and may be worth repeating for the next two to four days.
  • Flying itself can be very tiring, if you are prone to tiredness or fatigue the effects of jet lag can be more pronounced. General exercise in the weeks up to a flight can help reduce fatigue.


  • You should remain hydrated while flying by taking in bottled water and electrolytes, it is also advisable that you forgo drinking alcohol and caffeinated drinks (coffee, tea, fizzy drinks) when flying as these can dehydrate you as well.
  • Adopt the time-zone of your destination as soon as you board your flight. Make sure you get sunlight in the afternoon and avoid bright lights in the morning.
  • Drink water, and avoid alcohol, caffeine and fizzy drinks, including diet drinks.
  • If you have a cold try to avoid passing it to others, sufferers from asthma or other medical conditions should remember to take medication before and during a flight.
  • Select a flight on a Boeing 787 if you can. Oxygen levels are higher, the ‘altitude’ of the cabin is lower, and the electrochromic tinted windows can block a higher proportion of UVA and UVB light. These improvements should provide a healthier inflight environment.
  • Move around the aircraft as much as you can during flight.
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