Selected Reading
BOOKS
- Hydration Throughout Life. Ed: MJ Arnaud. John Libbey Eurotext, London
- Hydration and Aging. Ed: MJ Arnaud et al. Springer, New York. 1998
- Sports Drinks: Basic Science and Practical Aspects. Ed: RJ Maughan and R Murray. CRC Press, Boca Raton. 2001
- Thirst and Sodium Appetite: Physiological Basis. Ed: SP Grossman. Academic Press, San Diego. 1990
- Body Fluid Balance. Ed: ER Buskirk, SM Puhl. CRC Press, Boca Raton. 1996
- Water Science for Food Health. Ed: Z Berk et al. CRC Press, Boca Raton. 2001
- Thirst. Ed: BJ Rolls and ET Rolls. Cambridge University Press, Cambridge. 1982
ARTICLES
Water, hydration, and health
Popkin BM, D’Anci KE, Rosenberg IH. Water, hydration, and health. Nutr Rev 2010; 68(8): 439-58.
This review examines the current knowledge of water intake as it pertains to human health, including overall patterns of intake and some factors linked with intake, the complex mechanisms behind water homeostasis, and the effects of variation in water intake on health and energy intake, weight, and human performance and functioning. Water represents a critical nutrient, the absence of which will be lethal within days. Water’s importance for the prevention of nutrition-related noncommunicable diseases has received more attention recently because of the shift toward consumption of large proportions of fluids as caloric beverages. Despite this focus, there are major gaps in knowledge related to the measurement of total fluid intake and hydration status at the population level; there are also few longer-term systematic interventions and no Con formato: Numeración y viñetas Con formato: Numeración y viñetas published randomized, controlled longer-term trials. This review provides suggestions for ways to examine water requirements and encourages more dialogue on this important topic.
Water as an essential nutrient: the physiological basis of hydration
Jéquier E, Constant F. Water as an essential nutrient: the physiological basis of hydration. Eur J Clin Nutr 2010; 64(2): 115-23
How much water we really need depends on water functions and the mechanisms of daily water balance regulation. The aim of this review is to describe the physiology of water balance and consequently to highlight the new recommendations with regard to water requirements. Water has numerous roles in the human body. It acts as a building material; as a solvent, reaction medium and reactant; as a carrier for nutrients and waste products; in thermoregulation; and as a lubricant and shock absorber. The regulation of water balance is very precise, as a loss of 1% of body water is usually compensated within 24 h. Both water intake and water losses are controlled to reach water balance. Minute changes in plasma osmolarity are the main factors that trigger these homeostatic mechanisms. Healthy adults regulate water balance with precision, but young infants and elderly people are at greater risk of dehydration. Dehydration can affect consciousness and can induce speech incoherence, extremity weakness, hypotonia of ocular globes, orthostatic hypotension and tachycardia. Human water requirements are not based on a minimal intake because it might lead to a water deficit due to numerous factors that modify water needs (climate, physical activity, diet and so on). Water needs are based on experimentally derived intake levels that are expected to meet the nutritional adequacy of a healthy population. The regulation of water balance is essential for the maintenance of health and life. On an average, a sedentary adult should drink 1.5 l of water per day, as water is the only liquid nutrient that is really essential for body hydration.
Hydration in children
Manz F. Hydration in children. J Am Coll Nutr. 2007; 26(5 Suppl): 562S-569S.
Water supply is a basic public problem. In modern science, three periods with different approaches to define recommended water intake in adults can be distinguished. Pediatricians agree that hydration in children may be optimal only in breastfed infants. More data are required on the health effects of different hydration states and varying water intakes in particular age and gender groups to define optimal ranges of water intake. The fetus grows in an exceptionally well-hydrated environment. Water metabolism shows several peculiarities in preterm and term infants. Infant diarrhea remains a major topic of basic and clinical research. Water intoxication in infants, toddlers, and children is rare and can only be found in exceptional circumstances. Hydration status characterized by hyponatremia may play a role in the pathogenesis of febrile convulsions in toddlers. There is increasing indirect evidence that spontaneous drinking behavior of a population may be fixed and anchored in the age range of toddlers. Sex differences in hydration status are common, but not obligatory. What causes theses differences? What is behind the various circadian rhythms of urine osmolality in children? At what age and in what quantities can alcohol and caffeine consumption be tolerated? How can individual susceptibility be defined? Reflecting on the modern epidemic of obesity in children and adolescents, a public consensus concerning use and misuse of sweetened drinks seems mandatory. Dietary reference intakes of water refer to 24-hour intake. In nutritional counselling, food and mealbased dietary advice is primarily given. Young parents are confronted with a flood of advice of varying quality. Recommendations on fluid consumption should be collated and revised.
Hydration and health: a review
Benelam B, Wyness L. Hydration and health: a review. British Nutrition Foundation Nutrition Bulletin 2010; 35: 3-25
Water is essential for life and maintaining optimal levels of hydration is important for humans to function well.Water makes up a large proportion of our body weight (60% on average), distributed between the intracellular (inside cells) and extracellular (water in the blood and in between cells) compartments. Water is the major component of body fluids, such as blood, synovial fluid (fluid in the joints), saliva and urine, which perform vital functions in the body. The concentration of solutes (osmolality) in body fluids is closely controlled, and even very small changes in osmolality trigger a physiological response; either to increase body water by reducing urinary output and stimulating thirst; or to excrete excess water as urine. Generally, body water is maintained within narrow limits. However, if water losses are not sufficiently replaced, dehydration occurs. Extreme dehydration is very serious and can be fatal. More mild dehydration (about 2% loss of body weight) can result in headaches, fatigue and reduced physical and mental performance. It is also possible to consume too much water and in rare cases this can result in hyponatraemia (low levels of sodium in the blood). We can get water from almost all drinks and from some foods in the diet. Food provides about 20% on average and this could vary widely depending on the types of food chosen. We also get water from all the drinks we consume, with the exception of stronger alcoholic drinks like wines and spirits. All these can contribute to dietary water, but also have other effects on health both positive and negative. The major concerns with regards to beverages are their energy content and their effect on dental health. With obesity levels continuing to increase it is important for many in the population to control their energy intake, and drinks as well as foods must be considered for their energy content.With regards to dental health, there are two concerns; dental caries and dental erosion. Dental caries are caused by a reduction in pH due to bacterial fermentation of carbohydrates, and so the frequency of consumption of drinks containing sugars is a concern for risk of caries. Dental erosion occurs at a lower pH and is caused by the consumption of acidic foods and drinks, in particular, citrus juices and soft drinks containing acids. Individual water needs vary widely depending on many factors including body size and composition, the environment and levels of physical activity. Thus it is very difficult to make generic recommendations about the amount of water to consume. The FSA currently recommends drinking about 1.2 litres per day (about 6–8 glasses).
Free article available online
http://onlinelibrary.wiley.com/doi/10.1111/j.1467-3010.2009.01795.x/abstract
Water Physiology: Essentiality, Metabolism, and Health Implications
Kavouras SA, Anastasiou CS. Water Physiology: Essentiality, Metabolism, and Health Implications. Nutr Today. 2010; 45(6S): S27-S32
Water is the most abundant molecule in the human body that undergoes continuous recycling. Numerous functions have been recognized for body water, including its function as a solvent, as a means to remove metabolic heat, and as a regulator of cell volume and overall function. Tight control mechanisms have evolved for precise control of fluid balance, indicative of its biological importance. However, water is frequently overlooked as a nutrient. This article reviews the basic elements of water physiology in relation to health, placing emphasis on the assessment of water requirements and fluid balance. Current recommendations are also discussed.
Free article available online
Hydration educational materials
Hydration: Fluids for Life
Written by Ann Grandjean EdD, FACN, CNS and Sheila M. Campbell, PhD, RD. This monograph from the North America branch of the International Life Sciences Institute (ILSI-NA). provides readers with an overview of current knowledge related to the functions of water, methods of determining hydration status, sources of water in the diet, and specific considerations for infants, children, physically active individuals, and the elderly. Recommended intakes, as specified in the 2004 Dietary Reference Intakes for water, are also covered. Posted with permission.
The two following publications were produced by The Beverage Institute for Health and Wellness and they provide information about hydration and the importance of staying adequately hydrated. Posted with permission.
Nutrition for Athletics: A Practical Guide to Eating and Drinking for Health and Performance in Track and Field
Written by Professors Louise Burke (Australia) and Ron Maughan (UK). This booklet is based on the conclusions of the International Association of Athletics Federations (IAAF) Consensus Conference on Nutrition for Athletes held in Monaco in April 2007. It was supported through The Coca-Cola Company’s partnership with the IAAF via the POWERADE brand. Posted with permission.
Nutrition for Athletes: A Practical Guide to Eating for Health and Performance
Revised and Updated in March 2008. This booklet was developed by the Nutrition Working Group of the IOC in close collaboration with the IOC Athletes’ Commission and is based on an International Consensus Conference held at the International Olympic Committee (IOC) in Lausanne in June 2003. The Coca-Cola Company, via the POWERADE brand, partnered with the IOC’s Medical Commission to update this publication to help to spread the information in a worldwide campaign to athletes at all levels. Posted with permission.
Nutrition for Football
Prepared for the FIFA Sports Medical Committee by Professor Ron Maughan (UK) Professor Louise Burke (Australia) and Dr. Donald T. Kirkendall, (USA). Based on an International Consensus Conference held at FIFA House in Zurich September 2005. This booklet was created through a partnership between The Coca-Cola Company, via the POWERADE brand, FIFA and the FIFA Medical Assessment and Research Centre (F-MARC) to provide athletes with practical information in advance of the 2006 FIFA World CupTM;. Posted with permission.
Continuing Medical Education
Hydration and Health Promotion
Kolasa K, Lackey C. J., Grandjean AC. Hydration and Health Promotion. Nutrition Today 2009; 44(5): 190-201
While the relation between hydration status and physical activity (military operations, sports performance) has been an area of extensive research, more recently, researchers have begun examining the relation between hydration status and health, acute and chronic diseases, and cognitive performance. On November 29 and 30, 2006, the International Life Sciences Institute North America Technical Committee on Hydration organized a conference on hydration and health promotion. This article is an overview of that conference.