While it is clear that humans cannot survive for longer than
several days without water, very little research has assessed
how average individuals' health is affected by drinking extra
fluids. Experts have claimed that ingesting water is helpful
for everything from clearing toxins and keeping organs healthy
to warding off weight gain and improving skin tone.
To investigate the true benefits of drinking water, Dan Negoianu,
MD, and Stanley Goldfarb, MD, of the Renal, Electrolyte, and
Hypertension Division at the University of Pennsylvania, in
Philadelphia, PA, reviewed the published clinical studies on
the topic. They found solid evidence that individuals in hot,
dry climates, as well as athletes, have an increased need for
water. In addition, people with certain diseases benefit from
increased fluid intake. But no such data exist for average,
healthy individuals. In addition, no single study indicates
that people need to drink the recommended "8x8" amount of water
each day. Indeed, it is unclear where this recommendation came
This scan of the literature included a look at studies related
to the notion that increased water intake improves kidney function
and helps to clear toxins. A variety of studies reveal that
drinking water does have an impact on clearance of various substances
by the kidney, including sodium and urea. However, these studies
do not indicate any sort of clinical benefit that might result.
Other studies have tested water's effects on the functioning
of organs. They indicate that water retention in the body is
variable and depends on the speed with which water is ingested-if
it is gulped quickly, water is more likely to be excreted, while
if it is sipped slowly, it is retained in the body. However,
no studies have documented any sort of benefit to organs based
on increased water intake, regardless of speed.
Drs. Negoianu and Goldfarb also investigated the theory that
drinking more water will make people feel full and curb their
appetite. Proponents say this may help people maintain their
weight and even help fight obesity. But studies remain inconclusive.
No carefully designed clinical trials have measured the effects
of water intake on weight maintenance.
Headaches also are often attributed to water deprivation, but
there are few data to back this up. Only one small trial has
addressed the question, and while trial participants who increased
their water intake experienced fewer headaches than those who
did not, the results were not statistically significant.
In addition, water has been touted as an elixir for improved
skin tone. While dehydration can decrease skin turgor, no studies
have shown any clinical benefit to skin tone as a result of
increased water intake.
The literature review by Drs. Negoianu and Goldfarb reveals
that there is no clear evidence of benefit to increasing water
intake. On the other hand, no clear evidence exists of a lack
of benefit. "There is simply a lack of evidence in general,"