Key Tips on Hydration Hydration for different climatic situations http://www.europeanhydrationinstitute.org/

1.
Key Tips on Hydration (Volume 3)
Hydration needs for different climatic situations
Index
• Key Tips on Hydration for holidays.
• Key Tips on Hydration for winter.
• Key Tips on Hydration for hot weather.
• Key Tips on Hydration for variety.

2. SUMMER HOLIDAYS
KEY TIPS
ON HYDRATION
Don’t forget to
consider your
hydration needs.
In a temperate climate about 2-3 L of water
is lost from our bodies each day, mainly as
urine but also as sweat, expired breath, and
faeces.
The total amount of water lost will depend on several factors, such as gender, body size, the level of
physical activity and the amount and type of clothing worn. Environmentalconditionsoftemperature
and humidity will also have an impact on water loss.
Sweating or perspiring is a skin-cooling mechanism that uses a great deal of water. Water diffusion
through the skin accounts for about 0.45 L per day. However, environmental temperature and humidity,
the presence of air currents, the amount of clothing worn and the level of physical activity are all
factors that will influence the actual amount of water lost1
.
For Heathcare Professional
distribution only
Are you about
to go away
on holiday?
Sweat losses will be higher when exposed to high temperatures, such as in
the summer or in any other hot environment, and these must be replaced.
Hydration requirements need to be considered both, duringtravelling and in the holidaydestination.
When taking a plane
The body tends to dehydrate while travelling on aeroplanes because air in the cabin is dryer (10-20%
humidity) than a typical, comfortable indoor environment (30-60% humidity) and this is due to the air
conditioning. Under these conditions skin dehydration symptoms can be observed (parched lips, dry
eyes, itchy eyes, etc.) and increased amounts of water are lost through the breath. Mild dehydration
occurring during long flights is one of the causes of an increased blood viscosity, which in turn may
increase the risk of deep vein thrombosis2
.
When travelling by plane, hydration levels can be maintained by drinking an additional 250 mL of
water per hour over your regular hydration needs.

3. KEY TIPS ON HYDRATION
You can find information about how to recognize signs and symptoms of mild dehydration, and
practical advice about hydration during hot weather in our series of educational materials:
Key Tips on Hydration: recognizing signs and symptoms of mild dehydration.
www.europeanhydrationinstitute.org/files/EHI_Key_Tips_on_Hydration_Signs_and_symptoms_of_mild_dehydration.pdf
Key Tips on Hydration: hot weather
http://www.europeanhydrationinstitute.org/files/EHI_Key_Tips_on_Hydration_Hot_Weather.pdf
1. EFSA Panel on Dietetic Products, Nutrition, and Allergies (NDA); Scientific Opinion on Dietary reference values for water. EFSA Journal 2010;
8(3):1459. Available online: www.efsa.europa.eu/en/efsajournal/pub/1459.htm 2. Hamada K, Doi T, Sakura M, Matsumoto K, Yanagisawa K, Suzuki
T, et al. Effects of Hydration on Fluid Balance and Lower-Extremity Blood Viscosity During Long Airplane Flights. JAMA 2002; 287: 844-5. 3. Manz F,
Johner SA, Wentz A, Boeing H, Remer T. Water balance throughout the adult lifespan in a German population. Br J Nutr 2012; 107(11):1673-81.
70-80%
from beverages (all types,
not just plain water)1,3
20-30%
typically comes from food and
It is calculated that of
the total water needed…
However, this may vary greatly
depending of the diet that an
individual chooses.1,3
If you travel by car
Driving in a hot car can lead to sweating with large losses of water and electrolytes. Even in an
air conditioned car, water losses can be high on a long drive. Maintaining adequate hydration
while driving is of great importance, because even with mild dehydration (loss of about1% of
body weight) reductions in physical and cognitive performance and in thermoregulation and
cardiovascular function can occur. With fluid deficits of 4%, more severe performance decrements
are observed as well as difficulties in concentration, headaches, irritability and sleepiness1
.
Frequent drinks of non-alcoholic beverages during a long automobile trip may help to reduce road
fatigue. The dryness caused by an air conditioning unit can be avoided by increasing the air’s moisture
levels and by hydrating the skin.
Have you checked the weather forecast at your destination?
It is important to keep an eye on the weather forecast, temperature and humidity in the city or region
you are visiting in order to adjust hydration levels accordingly.
SOME PRACTICAL ADVICE:
• Get to know your usual hydration needs and adjust them to the place you are visiting and the level
of activity you are planning.
• The hotter and more humid the weather is, and the higher the level of activity, the more water will
be needed. You can meet your hydration needs with a whole range of beverages and with food rich
in water. Take into account that:

4. Hydration in winter
KEY TIPS
ON HYDRATION For HeaLthcare Professional
distribution only
In cold climates, body fluid losses can be as high as those in hot climates because of high rates of
energy expenditure, use of heavy clothing and increased losses in urine1,2
.
Under normal conditions, urine and sweat are the main methods of water loss, but we also lose
water via the lungs and faeces. These losses vary widely depending on fluid intake, diet, activity level,
temperature and clothing2,3
.
Respiratory losses
Daily respiratory water loss is normally about 250 to 350 mL/day for sedentary people, but can
increase to 500-600 mL/day for active people4
. The actual amount lost is influenced greatly by
environmental conditions (air temperature, humidity and wind speed) and the level of physical activity3
.
Winter activities such as skiing, snowboarding and ice-skating can therefore greatly increase
water loss, as can working or playing outdoors in the winter:
Breathing cold, dry air can increase respiratory water loss by approximately 5 mL/hour1
, so this
effect in itself is generally rather small for short exposures, but becomes meaningful when
living in very cold climates and exposed to these conditions for 24 hours per day.
Stressful physical exercise in cold weather can increase this loss to approximately 15 to 45
mL/hour1
because of the increased rate and depth of breathing.
Urine losses
As the body gets colder, water loss as urine increases due to a higher urination rate, a physiological
response known as cold-induced diuresis, which produces urine of low specific gravity* 2,3
.
* Specific gravity of urine is a measure of the concentration of solutes excreted.
INTAKE OUTPUT
Metabolism
400 mL
Food
500 mL
Drinking
1500 mL
Breathing
400 mL
Skin
400 mL
Urine
1500 mL
Faeces
100 mL
Example of normal water balance
In cold weather conditions,
additional water losses occur as
a result of increased urine and
respiratory water losses. Some
water is also lost through the
skin as a result of heavy clothing
and because sweat evaporates
quickly in cold, dry air.

5. KEY TIPS ON HYDRATION
70-80%from beverages
(all types, not just plain water)2,7
20-30% typically comes
from food
and about
However, this may vary greatly
depending of the diet that an
individual chooses.2,7
Practical tips to stay hydrated during the winter
Drink plenty of fluids, especially when exercising or working outdoors.
Drink regularly even when not thirsty as the sensation of thirst is reduced in cold
weather, and this can lead to dehydration5
.
Meals play an important role in helping to stimulate the thirst response causing the
intake of additional fluids and restoration of fluid balance6
.
Meals also provide water; it is calculated that of the total water needed:
Avoid excessive amounts of heavy clothing as it can cause significant sweating and
water and mineral salt loss.
Although urine colour is generally a useful index of hydration status*, this may not
be true in the cold when the cold stress may lead to an increased rate of production
of diluted urine.
The skin should also be cared for, as cold, dry air outdoors and indoor heating
contribute to the removal of water from the skin, causing dry, cracked skin9
.
* See our educational material about how to measure hydration status at:
www.europeanhydrationinstitute.org/educational_materials.html
1. Freund BJ, Young AJ. 1996. In: Buskirk ER, Puhl SM, eds. Body Fluid Balance: Exercise and Sport. Boca Raton, FL: CRC Press. Pp. 159–181. 2. EFSA
Panel on Dietetic Products, Nutrition, and Allergies (NDA). EFSA Journal 2010; 8(3):1459. Available at: www.efsa.europa.eu/en/efsajournal/pub/1459.
htm 3. Panel on Dietary Reference Intakes for Electrolytes and Water (2005) Dietary reference intakes for water, potassium, sodium, chloride, and
sulphate. National Academy Press: Washington DC. 4. Hoyt RW, Honig A. 1996. In: Buskirk ER, Puhl SM, eds. Body Fluid Balance: Exercise and Sport.
Boca Raton, FL: CRC Press. Pp. 183-196. 5. National Research Council. Nutritional Needs in Cold and High-Altitude Environments: Applications for
Military Personnel in Field Operations. Washington, DC: The National Academies Press, 1996. p. 170. 6. Maughan RJ, Leiper JB, Shirreffs SM. Eur
J Appl Physiol Occup Physiol 1996;73(3–4):317-325. 7. Manz F, Johner SA, Wentz A, et al. Br J Nutr 2012; 107(11):1673-81. 8. Kolasa KM, Lackey CJ,
Grandjean AC. Nutrition Today 2009;44:190-201. 9. Weber TM, Kausch M, Rippke F, et al. J Clin Aesthet Dermatol. 2012;5(8):29-39.

6. IN HOT WEATHER
KEY TIPS
ON HYDRATION
Symptoms of
dehydration
• MILD (around 1% of body weight).
Symptoms may include: thirst, headache,
weakness, dizziness, feeling tired and
lethargic.
• MODERATE (around 4% of body weight).
Symptoms may include: Dry mouth, little or
no urine, sluggishness, rapid heartbeat, lack
of skin elasticity.
• SEVERE (10% or more of body weight).
Symptoms may include: Extreme thirst, no
urine, rapid breathing, altered mental state,
cold, clammy skin.
Severe dehydration is a life-threatening
medical emergency and can be fatal.
For HeaLthcare Professional
distribution only
Hot weather conditionscan increase the body temperature resulting in serious stresses
for the body, placing it in greater danger of injury (heat cramps, heat exhaustion or heat stroke) or
in extreme conditions, death.
Sweating or perspiration is one of the mechanisms used by the body to cool itself in
conditions of heat. This water loss is often accompanied by disturbances in the body’s mineral salt
or electrolyte balance – especially disturbances in the concentrations of sodium and potassium.
That’s why, besides usual water losses (2-3 L/day), water (and salt) lost as additional sweat must
also be replaced when we are exposed to high temperatures.
As environmental temperature rises, the risk of dehydration increases.
Dehydration symptoms should be carefully monitored, especially in those people particularly
susceptible to heat reactions:
- elderly people,
- young children,
- chronic invalids and those taking certain medications which increase the risk of dehydration, such
as diuretics,
- people with weight or alcohol problems.

7. KEY TIPS ON HYDRATION
To know more about the sources of water, please visit us at:
http://www.europeanhydrationinstitute.org/nutrition_and_beverages.html
1. Manz F, Johner SA, Wentz A, Boeing H, Remer T. Water balance throughout the adult lifespan in a German population. Br J Nutr 2011; 1-9 [Epub
ahead of print] 2. EFSA Panel on Dietetic Products, Nutrition, and Allergies (NDA); Scientific Opinion on Dietary reference values for water. EFSA
Journal 2010; 8(3):1459. Available online: http://www.efsa.europa.eu/en/efsajournal/pub/1459.htm
The Panel on Dietetic Products, Nutrition and Allergies from the European Food Safety Authority (EFSA)2
issued reference
intakes for water in 2010. These are defined as total water intake, which is water from beverages (including drinking water)
and from food moisture. It is normally assumed that the contribution of food to total dietary water intake is 20 to 30%, while 70
to 80% is provided by beverages. This relationship is not fixed and depends on the type of beverage and on the choice of foods.
70-80%
from beverages (all types,
not just plain water)1,2
20-30%
typically comes from food and
It is calculated that of
the total water consumed…
However, this may vary greatly
depending of the diet that an
individual chooses.1,2
Some tips to ensure proper hydration of the body in hot weather.
Reduce water loss:
• In Summer, avoid going out in the hottest temperatures (11 to 16 h in Europe).
• If outside during these times, wear a hat, and light clothes.
• Reduce intensity and duration of exercise.
• Avoid badly ventilated places, close the shutters during the day and do not open the windows
before the outside temperature has dropped (at night).
• Ask for advice about any medications you are taking, especially if they increase the risk of
dehydration.
• Monitor your weight. In the short term (1-2 days), any weight that is gained or lost is probably
water.
Learn to recognise signs of dehydration and heat stroke:
• These are neither specific nor sensitive, but monitor headaches, fatigue, thirst.
Increase fluid intake:
• Ensure adequate water intake during the whole day, and pay special attention to the needs of
the most susceptible people.
• Drink regularly even when you are not thirsty.
• Eat food which is rich in water and avoid excess alcohol.

8. HOW VARIETY CAN HELP HYDRATION
KEY TIPS
ON HYDRATION For HeaLthcare Professional
distribution only
Given the particular importance of beverages in ensuring
our hydration, it is important to know that:
• Plain water is a significant source of liquid intake for most people, but many beverages
like juices, milk, soft drinks, coffee and tea are more than 85% water and are therefore an
important source of water.
• In addition to thirst, habit is very important in determining what and when we drink.
• Having available a variety of beverages may result in people drinking up to 50% more liquids
than if only water was available, as shown in a study of fluid intake of runners on a treadmill.3
• The pleasant taste of beverages is the reason why many people choose to drink beverages
like soft drinks, tea, milk, etc. instead of plain water.
• All non-alcoholic beverages and some weak alcoholic beverages hydrate and contribute to
an adequate hydration, including those containing caffeine such as coffee, tea and some soft
drinks.
• The role of variety in hydration has been recognised by International organisations such
as the International Life Sciences Institute (ILSI)4
and the European Food Safety Authority
(EFSA)2
and it is particularly important for population groups that may be vulnerable to
dehydration including children and elderly people.
• EFSA adequate intake advice for water relates to water from all sources in the diet (including
plain water, food and beverages).2
Please see our website to know more about the contents of water of different foods and drinks:
www.europeanhydrationinstitute.org/hydration_and_nutrition.html
70-80%from beverages
(all types, not just plain water)1,2
20 -30%typically comes from food
and about
It is calculated that of the total water consumed, about
However, this may vary greatly
depending of the diet that an individual
chooses.1,2

9. KEY TIPS ON HYDRATION
Including different beverages in the diet can also provide other benefits:
For example:
• Many beverages provide important nutrients such as vitamins, antioxidants and electrolytes
that contributes to our daily needs.
• Fruit juices can contribute to the five portions of fruit and vegetables that we are recommended
to consume each day.
• Sport drinks contain small amounts of sugar and electrolytes that help to reduce water, mineral
and energy imbalance due to physical exertion.
• Caffeinated drinks such as coffee can provide a stimulus when tired.
Although a variety of beverages contributes to hydration, it is important to take into account that
unlike plain water, beverages often contain calories and therefore they contribute to the daily energy
intake. The wide variety of low-calorie and no-calorie drinks available nowadays helps to reduce
this contribution. Guideline Daily Amounts (GDAs) are available in most countries to help people to
make informed choices about the products they buy.
A variety of sources,
colours and tastes is
important towards
achieving the
necessary liquid
intake for optimal
hydration and to
meeting nutritional
needs.
1. Manz F, Johner SA, Wentz A, Boeing H, Remer T. Water balance throughout the adult lifespan in a German population. Br J Nutr 2011;
1-9 [Epub ahead of print] 2. EFSA Panel on Dietetic Products, Nutrition, and Allergies (NDA); Scientific Opinion on Dietary reference
values for water. EFSA Journal 2010; 8(3):1459. Available online: http://www.efsa.europa.eu/en/efsajournal/pub/1459.htm 3. López-
Román J, Martínez Gonzálvez A, Luque A,Villegas García JA. Estudio comparativo de diferentes procedimientos de hidratación durante
un ejercicio de larga duración. Archivos de Medicina del Deporte 2008; 25(123): 435-441. 4. ILSI Scientific Consensus Statement
regarding the Importance of Hydration and Total Water Intake for Health and Disease. J.Am Coll Nutr 2007; 26(S): 529-623.

10.
http://www.europeanhydrationinstitute.org/