High blood pressure, and high cholesterol are adaptations by the body to the problem of insufficient water. A shortage of water in the body is first handled by closing off some capillaries. When this happens the areas served by those capillaries can then become unhealthy or diseased in some way. When these capillary networks are closed down, they provide an obstacle to the movement of blood and the blood pressure must go higher to push through the area. When the water shortage is greater than can be accommodated by a shut-off of some of the capillaries, then the shortage of water is made up from the liquid in the arteries. About 65% of the water shortage is taken from water inside the cells. These cells become dehydrated. Dehydrated cells become diseased much more easily than cells hydrated with the proper amount of water.
About 25% of the water shortage is taken from the water outside the cells. This reduction in water means that the blood becomes thicker. Thicker blood needs to be pushed harder to move it along - high blood pressure.
heart disease and blood pressure
About 10% of the water shortage is taken from the volume of liquid moving through the arteries. When there is a smaller volume of blood in the arteries, the arteries MUST get smaller to avoid air pockets from being formed. Smaller tubes require a higher blood pressure to push the supply of blood needed by the body.

So, 2 of the areas where the body takes water during a shortage will cause an increase in blood pressure.

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