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Role Of Water in High Blood Pressure
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while when reading advice for reducing blood pressure,
sometimes drinking water(H2O) is recommended. However, authority websites including the National
Heart, Lung and Blood Institute and the Mayo Clinic do not mention drinking water(H2O) to decrease
blood pressure, when discussing treatments and social lifestyle changes.
Then Why should some articles say that drinking water(H2O)
lowers blood pressure?
Role of water in High blood
pressure.
The basic idea that drinking water(H2O) will lower blood
pressure seems to come from the idea that when water(H2O) is taken in large quantity, that
sodium(Na) which is responsible for retaining water(H2O) inside the body, will be flushed out of
the body and as a result pressure will drop.
After all, several classes of diuretics are very effective at
reducing blood pressure like thiazide diuretics. These diuretics function by increasing the loss
of sodium(Na) from the body and an increased volume of urine. Both the loss of sodium(Na) from
the blood and decreasing the blood volume result in decreased high blood pressure. So, if
medicine, that effectively lower blood pressure in most people, work by increasing the volume of
urine and the amount of sodium(Na) in the urine, then drinking more water(H2O) should do the
same thing?
Unfortunately, there is a problem with this idea. To
understand why, it is necessary to understand that the body very tightly controls the levels of
fluid and ions such as sodium(Na) and calcium. For optimal functioning, the body has evolved a
wide range of control processes that are involved in keeping many ions and fluid levels within a
narrow range.
Diuretics act on parts of the nephron system in kidney that
control sodium(Na). For instance thiazide diuretics bind to, and inhibit, a protein called the
Na/Cl symporter (Na=sodium(Na), Cl=chloride) that controls the amount of sodium(Na) that is
reabsorbed back into the blood from the urine that is being formed. The result is that the body
recovers less sodium(Na) from the urine as it is being formed, and so more sodium(Na) is lost
along with more water(H2O) in urine. So diuretics affect the regulatory system and change a part
of this.
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water(H2O) has no impact on the sodium(Na) or fluid control system
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so it will not change the total amount of sodium(Na) in the
urine, or change the blood volume. Drinking more water(H2O) will increase the volume of urine as
the body regulates fluid levels, to keep the blood volume stable. Additionally, the same amount
of sodium(Na) (and other ions etc.) in a bigger volume will increase volume of urine.
Think about the color of urine. If not much fluid has been
consumed, or there has been a lot of sweating, there will a small quantity of urine with a
strong turbid yellow color (from urobilin). If a person is well hydrated, there is more urine
with a pale or white color. Same thing with sodium(Na), In a healthy individual, the greater the
volume of urine due to increased fluid intake, the lower the concentration of
sodium(Na).
So the bottom line is that, generally, increasing the amount
of water(H2O) that is consumed will not increase the amount of sodium(Na) lost by the blood, so
blood pressure will not be decreased.
In fact, drinking water(H2O) can actually cause a very short
term increase in blood pressure in some people, particularly those with some types of very low
blood pressure. This is only temporary and has no long term impact on blood pressure. This is
very similar to a pipe, and we close its one end, and add more and more water from other side of
pipe, then pressure inside the pipe will be increased. Similar is the case with blood pressure
vessels.
So the idea is, Keeping hydrated is good for health, but
overhydration has no benefit for lowering your blood pressure (Hypertension).
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