ehi key tips on hydration volume 2

Key Tips on Hydration (Volume 2)

Hydration needs for different activities

Index

• Key Tips on Hydration for studying.

• Key Tips on Hydration for physical activity

• Key Tips on Hydration for travelling.

• Key Tips on Hydration for sport.

• Key Tips on Hydration for the workplace.

Hydration wHile studying

KEY TIPSON HYDRATION For HeaLtHcare ProFessionaL

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Dehydration can adversely influence cognitive function1,2, and this is important when considering tasks such as studying.

It has been observed that when mild dehydration occurs (i.e. when 2-4% of body water is lost).

In situations where less severe dehydration occurs (such as when refraining from drinking for a relatively short period of time – up to a few hours), studies have generally failed to find evidence of cognitive impairment2.

Studies finding a relationship between dehydration and cognitive performance have to be interpreted with caution to determine the effects of dehydration independently of the effects of other stressors (e.g. thermal and physical stress, fatigue, etc.)3.

Nevertheless, on the basis of the known physiological effects of dehydration in the brain, the stress associated with dehydration itself could be considered a unique stressor with unique effects that may or may not be similar to those of other stressors. This supports the notion that adequate hydration status is of importance when facing cognitive tasks. The extent and duration of dehydration leading to cognitive impairment, and the cognitive functions most affected remain to be investigated4.

adequate hydrationis important for optimal functioning of the brain. when an individual is well hydrated, brain cells are better supplied with fresh, oxygen-laden blood, and the brain remains alert.

Short-term memory,

can be impaired1attention, and

arithmetic efficacy

Greater tiredness,

have also been reported2reduced alertness, and

lower levels of concentration

KEY TIPS ON HYDRATION

PRACTICAL TIPS TO STAY HYDRATED WHILE STUDYING

Before going to school, high-school or university, it is important to ensure that hydration status is adequate: breakfast should include enough liquid to achieve this. two studies have demonstrated that children commonly start the day at school partially dehydrated5,6.

water should be available throughout the day and drinks should be taken regularly especially if the environment is warm.

teachers may need to make sure that there are opportunities for drinking during the school, high-school or university day and that students are reminded to make use of these opportunities. Families should also be aware of this.

special attention should be given to meal times because:

eating helps to stimulate the thirst response causing the intake of additional fluids and restoration of fluid balance7.

Meals provide an important part of the water consumed during the day and it should be remembered that of the water intake in the diet:

educating pupils to assess their own hydration status can also be valuable* and urine colour provides a useful estimate of the hydration status during everyday activities10.

70-80%from beverages(all types, not just plain water)2,9

20-30% typically comes from food and about

However, this may vary greatly depending of the diet that an individual chooses.2,9

* see our educational material about how to measure hydration status at:www.europeanhydrationinstitute.org/educational_materials.html

1. Gopinathan PM, Pichan G, Sharma VM. Arch Environ Health 1988;43:15-7. 2. Szinnai G, Schachinger H, Arnaud MJ, et al. Am J Physiol Regul Integr Comp Physiol 2005;289:R275–R280. 3. Institute of Medicine: Dietary reference intakes for water, potassium, sodium, chloride, and sulfate. Washington, DC: The National Academies Press, 2005. 4. Lieberman HR. J Am Coll Nutr. 2007;26(5 Suppl):555S-561S. 5. Bonnet F, Lepicard EM, Cathrin L, et al. Ann Nutr Metab. 2012; 60(4):257-63. 6. Assael BM, Cipolli M, Meneghelli I, et al. J Nutr Disorders Ther 2012;2:3. 7. Maughan RJ, Leiper JB, Shirreffs SM. Eur J Appl Physiol Occup Physiol 1996;73(3–4):317-25. 8. 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 9. Manz F, Johner SA, Wentz A, et al. Br J Nutr 2012; 107(11):1673-81. 10. Kolasa KM, Lackey CJ, Grandjean AC. Nutrition Today 2009;44:190-201.

HYDRATION AND PHYSICAL ACTIVITY

KEY TIPSON HYDRATION

Physical work performance is usually decreased when dehydration exceeds about 1-2% of body weight2:

•Prolongedexercise intheheatwithdehydrationcorresponding to a loss of only 1% of body weight increases body temperature, which is a consequence of both reduced sweating and reduced skin blood flow induced by dehydration2.

•Abodywaterlossequivalenttomorethanabout2% of body mass induced by exercise in the heat has been shown to impair performance in a widevarietyoftestsofbothphysicalandmentalperformance3.

For HeaLtHcare ProFessionaL distribution onLy

In general, it is necessary to drink during exercise only when sweat losses are high enough to affect performance or when exercise has begun in a dehydrated state. During exercise, drinking should occur regularly, but the frequency of drinking and the amount consumed will depend on many factors, including:

•intensityanddurationofexercise•weatherconditions•physicalcharacteristicsoftheindividual:body

weight and sweating characteristics. Fluids consumed during exercise can play a number of roles, including making one feel more comfortable, replacing a body fluid deficit, and providingameanstoconsumeotheringredients.

Replenishingliquids

SweATLUNGSURINe

FAeCeS

Duringprolongedphysicalactivity,bodywaterlossesareprimarilycausedbysweat,althoughurineandrespiratoryfluidlossesalsohaveanimportantcontribution1.


70-80%from beverages(all types, not just plain water)4,5

20-30%typically comes from food and about

When it is helpful to dRink duRing exeRcise•Itisseldomnecessarytodrinkduringexercise that lasts less than about 40 minutes or when intensityislow,providedthatthehydrationstatuswasoptimalatthestart.Plainwateroranynon-alcoholicbeverageisperfectlyadequateinthesesituationsifsomethingisneeded.

•When the exercise lasts longer than about 30-40 minutes, sports drinks may be better than water2. One key benefit is that they can reduce the sensation of effort, making exercise seem easier.Therefore,theindividualwillbemorelikelytoenjoytheexerciseprogramandmorelikely to stick with it.

However, this may vary greatly depending on the diet that an individual chooses4,5

1.CasaDJ,ClarksonPM,RobertsWO.AmericanCollegeofSportsMedicineRoundtableonHydrationandPhysicalActivity:ConsensusStatementsCurrent Sports Medicine Reports 2005, 4:115–127.

2.FujiN,HondaY,HayashiK,KondoN,NishiyasuT.Effectofhypohydrationonhypertermichyperpneaandcutaneousvasodilationduringexerciseinmen. J Appl Physiol 2008;105(5):1509-18.

3.CheuvrontSN,CarterR,SawkaM.Fluidbalanceandenduranceexerciseperformance.CurrSportsMedRep2003;2:202-8.4.EFSAPanelonDieteticProducts,Nutrition,andAllergies (NDA);ScientificOpiniononDietary referencevalues forwater.EFSAJournal2010;8(3):1459.Availableonline:www.efsa.europa.eu/en/efsajournal/pub/1459.htm.

5. 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].

In order to ensure an appropriate amount of water, it is important to take into account that of the total water consumed, about:

SUMMER HOLIDAYS

KEY TIPSON 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. Environmental conditions of temperature 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 aboutto go aWayon 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, during travelling and in the holiday destination.

When taking a planethe 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.


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.pdfKey Tips on Hydration: hot weatherhttp://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 ofthe 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:

Hydration for SportSperformance: practical guidance


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1. Sport sessions should be started well hydrated. The aim is to develop fluid practices over the day that keep pace with regular fluid needs as well as the additional losses from exercise or hot environments. As losses change, so should drinking practices. Fluid intake should be spread over the day.

2. A targeted drinking plan for training and competition should be developed. This should be based on several pieces of information including individual sweat losses*, the opportunities to drink, and feedback from individual feelings of comfort and thirst. Sweat losses and the success of the drinking plan during training sessions in different situations should be monitored (see overleaf).

3. Watch out for “salty sweaters”, they may need drinks with more salt and may need more salt in food when sweat losses are high. To check whether someone is a salty sweater, ask him/her to wear a black T-shirt in training and look for salt stains (white powder) under the arms and on the chest.

High salt losses may be a contributing factor in some cases of muscle cramp. Sports drinks with higher salt (sodium) levels (e.g. 300-500 mg sodium per 500 mL liquid) may help reduce the risk of cramps for some athletes.

Severe dehydration impairs performance and increases the risk of heat illness, but drinking too much can also be harmful or uncomfortable. Every athlete is different because they have different sweat losses and different opportunities to drink fluid during their workouts and events.

Every athlete needs a personal hydration plan and they have to play a role in developing this.

The following are three simple steps that may help to guide hydration practices:

* please consult www.europeanhydrationinstitute.org to find out how to estimate sweat losses and sweat rates.


* this should generally not exceed about 1-2% of body mass. if you lost more than this, you probably did not drink enough, and you should drink more next time. if you lost less, you might have drunk too much. drinking so much that you gain weight during competition is seldom likely to be a good idea. the only time you might need to do this is when you have been dehydrated at the start of the event.

please consult www.europeanhydrationinstitute.org for more information about hydration in sports performance.

How To moniTor SwEAT LoSSES And THE SuccESS oF THE drinking pLAn during TrAining SESSionS in diFFErEnT SiTuATionS.Ask the people you are advising to consider the following questions every time they practice sports in different situations in order to adjust water intake according to the answers:

•Howdidyoufeel?

•Howdidyouperform?

•wHatwasyourweigHtlossovertHesession?*

•diditmakeyoufeeluncomfortable?

•didyoutaketimeouttodrinktHatwasunnecessary?

Hydration in tHe work place


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Water needs depend on gender and age but are also influenced by a variety of lifestyle factors; these include the level of physical activity and environmental factors such as temperature, relative humidity and air movement1. Such variables can differ greatly from one working environment to another and as many people spend a considerable percentage of their week at work, ensuring adequate hydration in the workplace is an important consideration.

Working in a warm environment can result in substantial water losses from the body, mainly in the form of sweat. The magnitude of such losses is dependent primarily on work intensity and duration, although sweat rates can differ between various work activities and between individuals2. Dehydration may occur if water lost exceeds water consumption.

Hydration in the work place is a specific concern because dehydration can affect productivity, safety, cost, and morale3.

conseQuences oF deHydration• Dehydrationresultsinanincrease in core temperature of about 0.1–0.2°C with

each 1% of dehydration4.

• Dehydrationcanalsoincrease the heart rate, which is typically accompanied by an increase in an individual’s subjective rating of perceived exertion to perform an exercise task3.

• Whendehydrationexceedsabout2%ofbodyweight,physical work capacity is diminished5.

• Dehydrationhasalsobeenshowntoadversely influence decision-making and cognitive performance, which may contribute to a decline in productivity and could be associated with an increased risk of work-related accidents3.


PRACTICAL ADVICE TO STAY HYDRATED IN THE WORK PLACE

preventing dehydration in the work place could involve a combination of strategies that might include the following3:

•Assessing hydration status*: urine colour provides a quick and useful estimate of hydration state during everyday activities6.

• Inclusion of practices that encourage fluid intake. provision of water fountains and vending machines may encourage workers to drink more often. improving access to bathroom facilities may also enhance liquid consumption, especially among women.

•Education: informing individuals (especially those who work in hot environments) about hydration assessment, signs and risks of dehydration, and strategies to maintain hydration while working, can reduce dehydration in the workplace3.

as well as encouraging fluid intake an education and hydration program at work should stress the importance of consuming meals which include food rich in water, because:

- Meals play an important role in helping to stimulate the thirst response causing the intake of additional fluids and restoration of fluid balance7.

- it is calculated that of the total water consumed:

80%from beverages(all types, not just plain water)1,8.

20%typically comes from foodand about

However, this may vary greatly depending of the diet that an individual choices1,8

* See our educational material about how to measure hydration status at:www.europeanhydrationinstitute.org/educational_materials.html

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. Sawka MN, Wenger CB, Pandolf KB. In Fregly MJ and Blatteis CM (eds): Handbook of Physiology, New York: Oxford University Press, pp. 157–185, 1996. 3. Kenefick RW, Sawka M. J Am Coll Nutr 2007;26:597S-603S. 4. Sawka MN, Francesconi RP, Young AJ, Pandolf KB. JAMA 1984;252:1165-9. 5. Institute of Medicine: Dietary reference intakes for water, potassium, sodium, chloride, and sulfate. Washington, DC: The National Academies Press, 2005. 6. Kolasa KM, Lackey CJ, Grandjean AC. Nutrition Today 2009;44:190-201. 7. Maughan RJ, Leiper JB, Shirreffs SM. Eur J Appl Physiol Occup Physiol 1996;73(3–4):317-25. 8. Manz F, Johner SA, Wentz A, Boeing H, Remer T. Br J Nutr 2012; 107(11):1673-81.

http://www.europeanhydrationinstitute.org/

ehi key tips on hydration volume 2

Health & Medicine