Water and Hydration

Water is accounting for 50% - 60% of the body mass. Water contains no calories and has several electrolytes including calcium, chloride, fluoride, magnesium, potassium and sodium. Water is intricately involved in numerous functions of the body:
1. Regulate body temperature
2. Carries oxygen and nutrients to cells
3. Lubricates joints and protects spinal cord
4. Cushions organs and tissues
5. Promotes digestion and helps prevent constipation
6. Flushes out waste products through kidneys and liver
7. Serves as the medium for all energy reactions in the body
8. Transports mineral throughout cells of body

Water is stored in the intracellular fluid (ICF – 65% of body water) and extracellular fluid (ECF is make up of blood plasma and lymph – 35% of body water). Chloride, potassium and sodium participate in maintenance of ICF and ECF levels. Hypothalamus in the brain regulates the fluid levels in the body.

Daily Water Intake

An average amount of water expenses in a day:
· Lost from breathing, perspiring and bowel movement – about 1 litre
· Average urine outputs a day for adult – 1.5 litres
The Institute of Medicine (IOM) published its Dietary Reference Intake for water in February 2004 (Above Table). Note that the 8 glasses a day is equivalent to 1,893mL Myth has no scientific evidence.

Hydration and Health

Kidney stones
To prevent kidney stone, moderation intake of calcium oxalate (beverages such as beer, chocolate milk, teas and fruit juices), protein, sodium and alcohol, while increasing the intake of water and fiber (Hughes & Norman, 1992).

Cancer of the Bladder and Lower Urinary Tract
Decreased in water consumption is associated with bladder and lower urinary tract cancer which results in a greater concentration of carcinogens in the urine and prolonged contact with bladder mucous membranes (Altieri, La Vecchia, & Negri, 2003; Michaud et al., 2007). In some countries, the amount of carcinogens in the tap water is a concern.(Villanueva et al., 2006).

Colorectal Cancer
Low intake of water may risk the risk of colonrectal cancer by lengthening bowel transit time, thus increasing the contact of carcinogens within mucous membrances in the colon and rectum (Altieri, La Vecchia, & Negri, 2003).

Mental and Physical Performance
When there is water depletion exceeding 2% of body weight can reduce the mental (Grandjean & Grandjean, 2007) and physical (Murray, 2007) performance.

Mental Performance
· Reduce in visuomotor (visual perception by the brain)
· Psychomotor
· Cognitive performance

Physical Performance
· Motivation and effort
· Cardiovascular function (↓Cardiac o/p, ↓ plasma volume, ↓ heart filling, ↓ in skin blood flow, ↓ blood volume, ↓ blood plasma osmolality, ↓stroke volume, ↑heart rate, ↑blood viscosity)
· Metabolic reactions
· Thermoregulatory control mechanism.

Fluid Replacement and Endurance

Sweat is approximately 99% water and the rest consists of electrolyte sodium and chloride plus tiny amount of calcium, potassium, magnesium, iron, zinc copper and some water-soluble vitamins (Williams, 2005). The 3 heat syndromes related to dehydration are heat cramps, exhaustion and stroke and the effective treatment for dehydration is to replace lost fluids with cool water, and sports drinks containing electrolytes and a CHO solution scientifically proven helpful. The Table is the approximate guides (Cardwell, 2006; McArdle, Katch, & Katch, 2005). As a general rule, urine colour is a good “marker of water intake. Normal urine should be clear to amber (light yellow) and more yellow when takin vitamins and some medications. Dark yellow urine or a lower output than usual can indicate dehydration.

References

1. Altieri, A., La Vecchia, C., & Negri, E. (2003). Fluid intake and risk of bladder and other cancers. Eur J Clin Nutr, 57 Suppl 2, S59-68.
2. Cardwell, G. (2006). Gold Medal Nutrition (4th ed.): Human Kinetics.
3. Grandjean, A. C., & Grandjean, N. R. (2007). Dehydration and cognitive performance. J Am Coll Nutr, 26(5 Suppl), 549S-554S.
4. Hughes, J., & Norman, R. W. (1992). Diet and calcium stones. Cmaj, 146(2), 137-143.
5. Kravitz, L. (2008). The science of nature's most important Nutrient. IDEA Fitness Journal
6. McArdle, W. D., Katch, F. I., & Katch, V. L. (2005). Sports & Exercise Nutrition (2nd ed.). Baltimore: Lippincott Williams & Wilkin.
7. Michaud, D. S., Kogevinas, M., Cantor, K. P., Villanueva, C. M., Garcia-Closas, M., Rothman, N., et al. (2007). Total fluid and water consumption and the joint effect of exposure to disinfection by-products on risk of bladder cancer. Environ Health Perspect, 115(11), 1569-1572.
8. Murray, B. (2007). Hydration and physical performance. J Am Coll Nutr, 26(5 Suppl), 542S-548S.
9. Villanueva, C. M., Cantor, K. P., King, W. D., Jaakkola, J. J., Cordier, S., Lynch, C. F., et al. (2006). Total and specific fluid consumption as determinants of bladder cancer risk. Int J Cancer, 118(8), 2040-2047.
10. Williams, M. H. (2005). Nutrition for health, fitness, & sport (7th ed.): McGraw Hill.