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The role of hydration in the maintenance of health is increasingly recognized. Studies in healthy adults show that even mild dehydration impairs a number of important aspects of cognitive function such as concentration, alertness, and short-term memory. However, due to the lack of suitable tools for assessment of hydration status, the effects of hydration on other aspects of day-to-day health and well being remain to be demonstrated.1

There is increasing evidence that mild dehydration plays a role in the development of various morbidities. Positive effects of maintenance of good hydration are shown for urolithiasis, ( a formation of stony concretions in the bladder or urinary tract ) constipation, exercise asthma, hypertonic dehydration in the infant, and hyperglycemia in diabetic ketoacidosis, urinary tract infections, hypertension, fatal coronary heart disease, venous thromboembolism, and cerebral infarct, and bronchopulmonary disorders. For bladder and colon cancer, the evidence is inconsistent.2

Weather is also an important factor in dehydration. Frostbite and hypothermia are not the only health hazards associated with frigidly cold temperatures. Cold weather studies at the University of New Hampshire show increased risk for dehydration, a condition more commonly associated with hot weather. “People just don’t feel as thirsty when the weather is cold,” says Robert Kenefick, UNH associate professor of kinesiology. “When they don’t feel thirsty, they don’t drink as much, and this can cause dehydration.” The body is about two-thirds water, and when the total water level drops by only a few percent, we can become dehydrated. Kenefick says fluid deficits of 3 to 8 percent of body mass have been reported in individuals working in cold environments, and dehydration is a major problem with exercise in the cold.3

Hot weather can cause dehydration and you should be very careful to drink enough fluids. Whether you are mowing/trimming grass, working on a farm or in construction, exercising or even working in your yard or garden, you should be aware of how important it is to stay hydrated during the summer. Water could be looked at as the most essential ingredient to a healthy life. Water has many important functions in the body including: transportation of nutrients and elimination of waste, lubricating joints and tissues, temperature regulation through sweating and several other vital functions.4

Water is an essential nutrient for all persons; thus, maintaining a chronic state of optimal hydration is recognized to provide health benefits. Voluntary drinking is also a behavior influenced by numerous social and psychological cues. Therefore, whether "thirst-guided" drinking maintains optimal hydration status is a multifactorial issue. Thirst perception is typically assessed by subjective ratings using either categorical or visual analog scales; however, which instrument yields greater sensitivity to change in hydration status has not been examined. Ratings of thirst perception do not always yield predictable patterns of voluntary drinking following dehydration; therefore, perceived thirst and ad libitum drinking are not equivalent measures of human thirst. The recommendation "drink to thirst" is frequently given to healthy individuals during daily life. However, factors and conditions (e.g., age, disease) that influence thirst should be recognized and probed further.5

One way to determine if you are dehydrated is by taking the skin Turgor Test. To determine skin turgor, the health care provider grasps the skin on the back of the hand, lower arm, or abdomen between two fingers so that it is tented up. The skin is held for a few seconds then released.Skin with normal turgor snaps rapidly back to its normal position. Skin with decreased turgor remains elevated and returns slowly to its normal position.6

Under normal environmental conditions, fluid intake through changes in thirst sensations and regulation of loss by the kidneys. The average fluid requirement for adults is estimated to be 2 to 2.7 quarts per day. This is the volume needed to replace urine loss, insensible loss from skin and lungs, and loss in feces.7

Some athletes may need to increase intake of foods high in sodium chloride (salt), Some examples are pizza, ham, potato chips, or add salt to foods. Athletes who sweat profusely for a period of days, and are low in sodium intakes can experience heat cramps from sodium depletion.8

The best fluids are those that leave the stomach fast, contain little sodium, and less than 8% sugar (water). Avoid coffee and tea because they contain caffeine which increases water loss through urination. Alcoholic beverages also dehydrate by increasing urination. Pop and fruit juices contain more sugar than needed so they aren't absorbed as easily or quickly as water or commercial sports drinks. Commercial sports drinks contain about 5 to 8 percent sugar. These can be useful if you are participating in vigorous physical activity for longer than 1 to 4 hours.9

The role of water and hydration in physical activity, particularly in athletes and in the military, has been of considerable interest and is well-described in the scientific literature.10-11 During challenging athletic events, it is not uncommon for athletes to lose 6–10% of body weight in sweat loss, thus leading to dehydration if fluids have not been replenished. However, decrements in physical performance in athletes have been observed under much lower levels of dehydration, as little as 2%.12 Under relatively mild levels of dehydration, individuals engaging in rigorous physical activity will experience decrements in performance related to reduced endurance, increased fatigue, altered thermoregulatory capability, reduced motivation, and increased perceived effort.13-14 Rehydration can reverse these deficits, and also reduce oxidative stress induced by exercise and dehydration.15

How much fluid is enough? Flued needs are linked to energy expenditure. The more energy an athlete expends, the greater are his fluid needs. Why? Heat is a byproduct of energy production, and excess heat must be transferred from the body to the environment to maintain normal body temperature. Evaporation of sweat from the athlete’s body is the primary way of dissipating excess heat. Sweat loss varies among athletes and can exceed 1.5 liters per hour. To maintain adequate hydration, sweat loss must be replaced. Consuming 1.0 to 1.5 ml of fluid for each kilocalorie that is expended is optimal. Thus, an athlete who expends 5,000 calories a day needs 5,000 to 7,500 ml of fluid intake a day to maintain fluid balance. Fluid consumption includes all liquids plus water in foods. 16

References:

  1. Ritz P1, Berrut G. The importance of good hydration for day-to-day health. Nutr Rev. 2005 Jun;63

2.Manz F1Wentz ANutr Rev.

3.Contact Keeler, Sharon UNH Media Relations Cold Weather Increases Risk Of Dehydration www.ces.ncsu.edu

  4. NC Cooperative Extension Stay Hydrated in hot weather. www.ces.ncsu.edu

  5. Millard-Stafford M, Wendland DM, O’Dea NK, Norman TL. Thirst and hydration status in everyday life. Nutr Rev. 2012 Nov;70 Suppl 2:S147-51

  6. US National Library of Medicine Skin Turgor. www.nlm.nih.gov

  7. Baechle R. Thomas Earle W. Roger Essentials of Strength Training and Conditioning, Second Edition www.HumanKinetics.com

  8. Baechle R. Thomas Earle W. Roger Essentials of Strength Training and Conditioning, Second Edition www.Human Kinetics.com

  9. Rindels, Sherry Department of Horticulture ISU Entomology Horticulture and Home Pest News/Heat Safety June 20, 1997 issue, pp. 95-97

 10. Maughan RJ, Shirreffs SM, Watson P. Exercise, heat, hydration and the brain. J Am Coll Nutr. 2007;26:604S–612S. [PubMed]

 11. Sawka MN, Noakes TD. Does dehydration impair exercise performance? Med Sci Sports Exerc. 2007;39:1209–1217. [PubMed]

 12. Murray B. Hydration and physical performance. J Am Coll Nutr. 2007;26:542S–548S. [PubMed]

 13. Montain SJ, Coyle EF. Influence of graded dehydration on hyperthermia and cardiovascular drift during exercise. J Appl Physiol. 1992;73:1340–1350. [PubMed]

 14. Cheuvront SN, Carter R, 3rd, Sawka MN. Fluid balance and endurance exercise performance. Curr Sports Med Rep. 2003;2:202–208. [PubMed]

 15. Paik IY, Jeong MH, Jin HE, et al. Fluid replacement following dehydration stress during recovery reduces oxidative. Biochem Biophys Res Commun. 2009;383:103–107. [PubMed]

 16. btc.montana.edu/Olympics/nutrition/eat02.html Fluid Balance.

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