Key Tips on Hydration (Volume 2)Hydration needs for different activitiesIndex• 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 studyingKEY TIPSON HYDRATION For HeaLthcare Professionaldistribution onlyDehydration can adversely influence cognitive function1,2, and this is important when consideringtasks 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 arelatively short period of time – up to a few hours), studies have generally failed to find evidence ofcognitive impairment2.Studies finding a relationship between dehydration and cognitive performance have to be interpretedwith 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 stressassociated with dehydration itself could be considered a unique stressor with unique effects that mayor may not be similar to those of other stressors. This supports the notion that adequate hydrationstatus is of importance when facing cognitive tasks. The extent and duration of dehydration leadingto cognitive impairment, and the cognitive functions most affected remain to be investigated4.Adequate hydrationis important for optimalfunctioning of the brain.When an individual is wellhydrated, brain cells arebetter supplied with fresh,oxygen-laden blood, andthe brain remains alert.Short-term memory,can be impaired1attention, andarithmetic efficacyGreater tiredness,have also been reported2reduced alertness, andlower levelsof concentration
KEY TIPS ON HYDRATIONPRACTICAL TIPS TO STAY HYDRATED WHILE STUDYING Before going to school, high-school or university, it is important to ensure thathydration status is adequate: breakfast should include enough liquid to achievethis. Two studies have demonstrated that children commonly start the day at schoolpartially dehydrated5,6. Water should be available throughout the day and drinks should be taken regularlyespecially if the environment is warm. Teachers may need to make sure that there are opportunities for drinking duringthe school, high-school or university day and that students are reminded to makeuse 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 additionalfluids and restoration of fluid balance7. Meals provide an important part of the water consumed during the day and itshould be remembered that of the water intake in the diet: Educating pupils to assess their own hydration status can also be valuable* and urinecolour provides a useful estimate of the hydration status during everyday activities10.70-80%from beverages(all types, not just plain water)2,920-30% typically comes fromfood and aboutHowever, this may vary greatlydepending of the diet that anindividual chooses.2,9* See our educational material about how to measure hydration status at:www.europeanhydrationinstitute.org/educational_materials.html1. 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 IntegrComp 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. AnnNutr 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 Dietaryreference 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 ACTIVITYKEY TIPSON HYDRATIONPhysical work performance is usually decreasedwhen dehydration exceeds about 1-2% of bodyweight2:• Prolonged exercise in the heat with dehydrationcorresponding to a loss of only 1% of bodyweight increases body temperature, which isa consequence of both reduced sweating andreduced skin blood flow induced by dehydration2.• A body water loss equivalent to more than about2% of body mass induced by exercise in the heathas been shown to impair performance in awide variety of tests of both physical and mentalperformance3.For HeaLthcare Professionaldistribution onlyIn general, it is necessary to drink during exerciseonly when sweat losses are high enough to affectperformance or when exercise has begun ina dehydrated state. During exercise, drinkingshould occur regularly, but the frequency ofdrinking and the amount consumed will dependon many factors, including:• intensity and duration of exercise• weather conditions• physical characteristics of the individual: bodyweight and sweating characteristics.Fluids consumed during exercise can play anumber of roles, including making one feel morecomfortable, replacing a body fluid deficit, andproviding a means to consume other ingredients.ReplenishingliquidssweatLUNGSURINEFAECESDuring prolonged physical activity, body water losses are primarily caused by sweat, although urineand respiratory fluid losses also have an important contribution1.
KEY TIPS ON HYDRATION70-80%from beverages(all types, not just plain water)4,520-30%typically comes from food and aboutWhen it is helpful to drink duringexercise• It is seldom necessary to drink during exercise that lasts less than about 40 minutes or whenintensity is low, provided that the hydration status was optimal at the start. Plain water or anynon-alcoholic beverage is perfectly adequate in these situations if something is needed.• When the exercise lasts longer than about 30-40 minutes, sports drinks may be better thanwater2. One key benefit is that they can reduce the sensation of effort, making exercise seemeasier. Therefore, the individual will be more likely to enjoy the exercise program and morelikely to stick with it.However, this may vary greatly depending on the diet that an individual chooses4,51. Casa DJ, Clarkson PM, Roberts WO. American College of Sports Medicine Roundtable on Hydration and Physical Activity: Consensus StatementsCurrent Sports Medicine Reports 2005, 4:115–127.2. Fuji N, Honda Y, Hayashi K, Kondo N, Nishiyasu T. Effect of hypohydration on hypertermic hyperpnea and cutaneous vasodilation during exercise inmen. J Appl Physiol 2008;105(5):1509-18.3. Cheuvront SN, Carter R, Sawka M. Fluid balance and endurance exercise performance. Curr Sports Med Rep 2003;2:202-8.4. 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.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 [Epubahead of print].In order to ensure an appropriate amount of water, it is important to take intoaccount that of the total water consumed, about:
SUMMER HOLIDAYSKEY TIPSON HYDRATIONDon’t forget toconsider yourhydration needs.In a temperate climate about 2-3 L of wateris lost from our bodies each day, mainly asurine but also as sweat, expired breath, andfaeces.The total amount of water lost will depend on several factors, such as gender, body size, the level ofphysical activity and the amount and type of clothing worn. Environmentalconditionsoftemperatureand 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 diffusionthrough 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 allfactors that will influence the actual amount of water lost1.For Heathcare Professionaldistribution onlyAre you aboutto go awayon holiday?Sweat losses will be higher when exposed to high temperatures, such as inthe 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 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 airconditioning. Under these conditions skin dehydration symptoms can be observed (parched lips, dryeyes, itchy eyes, etc.) and increased amounts of water are lost through the breath. Mild dehydrationoccurring during long flights is one of the causes of an increased blood viscosity, which in turn mayincrease the risk of deep vein thrombosis2.When travelling by plane, hydration levels can be maintained by drinking an additional 250 mL ofwater per hour over your regular hydration needs.
KEY TIPS ON HYDRATIONYou can find information about how to recognize signs and symptoms of mild dehydration, andpractical 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.pdf1. 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, SuzukiT, 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)1,320-30%typically comes from food andIt is calculated that ofthe total water needed…However, this may vary greatlydepending of the diet that anindividual chooses.1,3If you travel by carDriving in a hot car can lead to sweating with large losses of water and electrolytes. Even in anair conditioned car, water losses can be high on a long drive. Maintaining adequate hydrationwhile driving is of great importance, because even with mild dehydration (loss of about1% ofbody weight) reductions in physical and cognitive performance and in thermoregulation andcardiovascular function can occur. With fluid deficits of 4%, more severe performance decrementsare 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 roadfatigue. The dryness caused by an air conditioning unit can be avoided by increasing the air’s moisturelevels 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 regionyou 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 levelof activity you are planning.• The hotter and more humid the weather is, and the higher the level of activity, the more water willbe needed. You can meet your hydration needs with a whole range of beverages and with food richin water. Take into account that:
Hydration for SportsPerformance: practical guidanceKEY TIPSON HYDRATION For HeaLthcare Professionaldistribution only1. Sport sessions should be started well hydrated. The aim is to develop fluidpractices over the day that keep pace with regular fluid needs as well as theadditional losses from exercise or hot environments. As losses change, so shoulddrinking practices. Fluid intake should be spread over the day.2. A targeted drinking plan for training and competition should be developed. Thisshould be based on several pieces of information including individual sweat losses*,the opportunities to drink, and feedback from individual feelingsof comfort and thirst. Sweat losses and the success ofthe drinking plan during training sessions in differentsituations should be monitored (see overleaf).3. Watch out for “salty sweaters”, they may need drinkswith more salt and may need more salt in food whensweat losses are high. To check whether someone isa salty sweater, ask him/her to wear a black T-shirt intraining and look for salt stains (white powder) under thearms and on the chest.High salt losses may be a contributing factor in somecases of muscle cramp. Sports drinks with higher salt(sodium) levels (e.g. 300-500 mg sodium per 500 mLliquid) may help reduce the risk of cramps for someathletes.Severe dehydration impairs performance and increases the risk of heat illness, but drinkingtoo much can also be harmful or uncomfortable. Every athlete is different because they havedifferent 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 arole 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.
KEY TIPS ON HYDRATION* This should generally not exceed about 1-2% of body mass. If you lost more than this, youprobably did not drink enough, and you should drink more next time. If you lost less, you mighthave drunk too much. Drinking so much that you gain weight during competition is seldom likelyto be a good idea. The only time you might need to do this is when you have been dehydrated atthe start of the event.Please consult www.europeanhydrationinstitute.org for more information about hydration insports performance.How to monitor sweat loSsesand the success of the drinkingplan during training sessions indifferent situations.Ask the people you are advising to consider the following questions every time they practicesports in different situations in order to adjust water intake according to the answers:• How did you feel?• How did you perform?• What was your weightloss over the session?*• Did it make you feeluncomfortable?• Did you take time outto drink that wasunnecessary?
Hydration in the work placeKEY TIPSON HYDRATION For HeaLthcare Professionaldistribution onlyWater needs depend on gender and age but are also influenced by a variety of lifestyle factors; theseinclude the level of physical activity and environmental factors such as temperature, relative humidityand air movement1. Such variables can differ greatly from one working environment to another andas many people spend a considerable percentage of their week at work, ensuring adequate hydrationin the workplace is an important consideration.Working in a warm environment can result in substantial water losses from the body, mainly in theform 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. Dehydrationmay 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• Dehydration results in an increase in core temperature of about 0.1–0.2°C witheach 1% of dehydration4.• Dehydration can also increase the heart rate, which is typically accompanied byan increase in an individual’s subjective rating of perceived exertion to performan exercise task3.• When dehydration exceeds about 2% of body weight, physical work capacity isdiminished5.• Dehydration has also been shown to adversely influence decision-making andcognitive performance, which may contribute to a decline in productivity andcould be associated with an increased risk of work-related accidents3.
KEY TIPS ON HYDRATIONPRACTICAL ADVICE TO STAY HYDRATED IN THE WORK PLACEPreventing dehydration in the work place could involve a combination of strategies thatmight include the following3:• Assessing hydration status*: urine colour provides a quick and useful estimate ofhydration state during everyday activities6.• Inclusion of practices that encourage fluid intake. Provision of water fountains andvending machines may encourage workers to drink more often. Improving access tobathroom 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 maintainhydration while working, can reduce dehydration in the workplace3. As well as encouraging fluid intake an education and hydration program at work shouldstress 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 comesfrom foodand aboutHowever, this may vary greatlydepending of the diet that anindividual choices1,8* See our educational material about how to measure hydration status at:www.europeanhydrationinstitute.org/educational_materials.html1. 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 Today2009;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.