LISTENING PART 4
You will hear a biology student talking about water and how much people
need to drink each day.
Now listen carefully and answer questions 31 to 40.
Student:
Hi everyone. My presentation today is looking at drinking water.
Now, we know that water is a vital nutrient for human life. But exactly
how much of it do we need to drink? Well, today I’m going to review
some of the research.
So, for example, there’s a common idea that we should drink 8 glasses
of water every day. But researchers say that the 8-glasses-a-day rule is a
myth. Some people might need more than 8 glasses, some a lot less. The
only group for whom the rule is useful seems to be the elderly, because
they don’t
always feel thirsty, even when their bodies are actually short
of water. So for them 8 glasses a day might be a good rough guide.
OK, let’s look next at what effects water has on the body. One issue of
interest is weight loss. And there are lots of theories about this. It’s been
claimed that dieters should drink more at night time, or drink when they
first wake up, but there’s no research to back this up. But actually, there
is some evidence from studies to show that
subjects who drank a lot of
water, and then had their meals, lost more weight. But that may only be
because the water filled them up and reduced their appetites.
I also read some of the research done by Dr Amaldi, who’s looked in
depth at this whole issue of drinking water. And one of his studies
does support the common claim that water is good for the stomach. In
particular, it seems to increase the rate at which digestion takes place,
which overall has a number of health benefits.
Another interesting study I read about took place in the US. And this
one was investigating the effects of dehydration – that is, not having
enough water in the body. And what the
US study indicated was that
when a subject was low on water, their body’s ability to regulate its
own temperature was compromised, compared to a properly hydrated
subject.
Now there’s another frequent claim about water that I was interested
in looking into. But in my reading anyway I could find no evidence at all
to support the idea that hydration improves
or enhances the skin in any
specific way. So that claim may be a bit of a myth as well.
Another interesting aspect of this concerns the brain. And I read about
a couple of research studies investigating how water intake may affect
brain function. In the first study, the research subjects were female. And
the less hydrated group were affected more frequently by headaches
compared to those who drank more water.
In the second study, the research subjects were all male. And this time,
a lack of water in the body was associated with a number of findings.
In particular, the subjects in this group reported
increased feelings of
anxiety when dehydrated.
So, in summary we can see that, yes, there are some health benefits from
drinking plenty of water. But in many of these studies, the benefit was
quite small. And it’s probably true that in general, on the internet and so
on, the benefits of drinking lots of water are overstated.
But what about the opposite – can you drink too much water? Well, it’s
possible, but it’s not a common problem. Actually,
the human body kind
of prevents us drinking too much. Australian researchers discovered
that when subjects were fully hydrated, they actually found swallowing
problematic – their bodies just wouldn’t allow it so easily. So that’s an
interesting finding.
It is true that people do occasionally become sick from drinking too
much water, although it is rare. So, I mean, there are recorded instances
of illness among athletes who have been encouraged to drink a lot, for
example.
According
to doctors, people who have drunk too much water, too
quickly, have become what’s called ‘hyponatremic’. Basically, this means
that the make-up of their blood has changed and it now contains such a
high proportion of salt that they suffer an adverse effect. But it’s very rare
for this sort of hyponatremia to be a dangerous condition.
So, based on the reading I’ve done, the best advice is to trust your body.
Drink water when you’re thirsty, but you probably don’t need to drink
more often than that.
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