Mineral water after a flight and a long evening

In short: humidity in an aircraft cabin sits at around 10 to 20%, and a long flight costs you a noticeable amount of fluid. Alcohol works as a diuretic, so sodium, potassium and magnesium leave along with the water. What to do: drink little and often, add mineral water and something salty. This is not a treatment, and if you feel really bad, see a doctor.

Why does a flight leave you dry?

Cabin humidity stays around 10 to 20%, drier than a desert. Moisture leaves through your breath and skin for every hour of the flight, and people usually forget to drink in their seat. Hence the dry mouth, the heavy head and the sluggishness after landing. A simple guide is a glass of water for every hour in the air. Coffee and alcohol on board add their own effect, and in the tropics, when you step out of the airport into the heat, dehydration catches up with you a second time.

• Dry cabin air pulls moisture out through your breath and skin
• A guide: a glass of water for every hour of the flight
• Coffee and alcohol on board dry you out even more
• After landing in the tropics, dehydration catches up with you again

Why alcohol leaves you dry

Alcohol suppresses the hormone that keeps fluid in the body, hence the frequent trips to the toilet and the dryness in the morning. Salts leave with the fluid, so water alone brings you back more slowly than you would like. A litre downed in one go in the morning works worse than a glass at a time over a couple of hours together with ordinary food. Do not overdo the salty food either: the WHO advises adults to stay under 2 g of sodium a day.

• Alcohol suppresses the hormone that retains fluid, hence the frequent trips to the toilet
• Salts leave along with the fluid, not just water
• A litre downed in one go in the morning works worse than a glass at a time over a couple of hours

Which water is easier on you

Mineral water of moderate mineralisation brings back both fluid and some of the salts: Narzan's label gives 50 to 450 mg/L of sodium plus potassium and 50 to 180 mg/L of magnesium. Essentuki No. 4 is saltier, at 2000 to 3000 mg/L of sodium plus potassium, which is why it is drunk by the glass rather than by the litre. Some people find fizz easier, others find it harder: if your stomach is unsettled, let the bottle stand open. Cool water goes down more easily than ice-cold, and sweet fizzy drinks and energy drinks will not help here.

• Mineral water of moderate mineralisation brings back both fluid and salts
• Some people find fizz easier, others harder, so go by how you feel
• Cool rather than ice-cold water goes down more easily
• Sweet fizzy drinks and energy drinks will not help

What water will not do

Mineral water does not cure a hangover and does not flush anything out of the body: that is the liver's job, and a glass of water will not speed it up. It returns fluid and some salts, nothing more. With kidney or heart conditions, high blood pressure or a prescribed salt restriction, discuss how much mineral water to drink with your doctor. Everything above is general information, standards and manufacturers' data, not medical advice.

• Mineral water does not cure a hangover and does not "flush out toxins"
• With kidney or heart conditions, or a salt restriction, discuss the routine with your doctor
• Everything above is general information and manufacturers' data

Sources

• WHO: sodium reduction (no more than 2 g a day)
• EFSA: water intake reference values, 2 L a day for women and 2.5 L for men (2010)
• GOST R 54316-2020: composition of Narzan and Essentuki No. 4 (table A.1)