Health authorities have historically suggested at
least eight glasses, eight fluid ounces each (240 ml),
of water per day (64 fluid ounces, or 1.89 litres),
and the British Dietetic Association recommends 1.8
The amount of water varies with the
individual, as it depends on the condition of the
subject, the amount of physical exercise, and on the
environmental temperature and humidity.
In the US, the
reference daily intake (RDI) for water is 3.7 litres
per day (l/day) for human males older than 18, and 2.7
l/day for human females older than 18 including water
contained in food, beverages, and drinking water.
common misconception that everyone should drink two litres (68 ounces, or about eight 8-oz glasses) of
water per day is not supported by scientific research.
Various reviews of all the scientific literature on
the topic performed in 2002 and 2008 could not find
any solid scientific evidence that recommended
drinking eight glasses of water per day.
people in hotter climates will require greater water
intake than those in cooler climates. An individual's
thirst provides a better guide for how much water they
require rather than a specific, fixed number. A more
flexible guideline is that a normal person should
urinate 4 times per day, and the urine should be a
light yellow color.
In terms of mineral nutrients
intake, it is unclear what the drinking water
contribution is. However, inorganic minerals generally
enter surface water and ground water via storm water
runoff or through the Earth's crust.
processes also lead to the presence of some minerals.
Examples include calcium, zinc, manganese, phosphate,
fluoride and sodium compounds. Water generated from
the biochemical metabolism of nutrients provides a
significant proportion of the daily water requirements
for some arthropods and desert animals, but provides
only a small fraction of a human's necessary intake.
There are a variety of trace elements present in
virtually all potable water, some of which play a role
For example sodium, potassium and
chloride are common chemicals found in small
quantities in most waters, and these elements play a
role (not necessarily major) in body metabolism. Other
elements such as fluoride, while beneficial in low
concentrations, can cause dental problems and other
issues when present at high levels. Water is essential
for the growth and maintenance of our bodies, as it is
involved in a number of biological processes.
Profuse sweating can increase the need for electrolyte
(salt) replacement. Water intoxication (which results
in hyponatremia), the process of consuming too much
water too quickly, can be fatal.
The human kidneys
will normally adjust to varying levels of water
intake. The kidneys will require time to adjust to the
new water intake level. This can cause someone who
drinks a lot of water to become dehydrated more easily
than someone who routinely drinks less.