What is dehydration?
Definition of dehydration
A lack of water in the body resulting from inadequate intake of fluids or excessive loss through sweating, vomiting, or diarrhoea (ref: Encarta Dictionary).
If you are dehydrated it means your body does not contain as much water as it requires. This is quantified as a 1% or greater loss of body weight as a result of fluid lossKleiner SM. Water: An essential but overlooked nutrient. J Am Diet Assoc 1999:99:201-7.
Even without perspiration, the normal daily turnover of water is approximately 4% of the total body weight in adults and 15% of total body weight in infants.
- In a 70kg adult, this is equivalent to 2.0-3.0 litres/day
- In a 7kg infant, this is equivalent to 1.0 litre/dayKleiner SM. Water: An essential but overlooked nutrient. J Am Diet Assoc 1999:99:201-7
Dehydration can result from losing too much fluid, for example through insufficient consumption of water, sweating, vomiting or diarrhoea.
Dehydration is classified as mild, moderate or severe – based on how much fluid is lost or not replenished.
Detrimental effects on cognitive and physical performance are known to be proportional to the degree of dehydration and is highly significant at 2% dehydration for all mental functions e.g. short-term memory, arithmetic efficiency, and visuomotor tracking; motor speed and attentionGopinathan et al. Role of Dehydration in Heat Stress-Induced Variations in Mental Performance. Arch Envir. Health 1988:Vol.43:No.1.
Urine is used as an index of fluid balance in the body. In an attempt to simplify urine analysis Dr Lawerence Armstrong published the first validated urine colour chart in 1994. This 8-colour scale includes colours from pale yellow, the colour of straw, (number 1) to brownish green colour (number 8). The chart is an easy way to monitor your hydration status – if your urine colour matches numbers 1-3 on the chart you are well hydrated, if your urine colour matches number 7 or darker you need to drink fluids. An example of the urine colour chart can be found in the publication “Performing in Extreme Environments” by Lawerence Armstrong PhDArmstrong, LE. Performing in Extreme Environments. Human Kinetcis.2000.
Find out more about how much water you should be drinking.