Fluids are needed within each cell to keep them juicy and round so they can function properly. Our organs can be considered water balloons sloshing around in the sea of water that is our abdominal cavity.
Water is the major ingredient in ALL the fluids necessary for our survival. Water also conducts electricity, which is important in many functions of the body, most famously, that of the heart. Electrocardiograms are used to measure the electrical charge in the heart, and pace-makers are given to regulate the charge in the heart. It is unlikely that any of that would be possible without water.
Remember that 75% of our bodies are made up of water, and 85% of our brains are made up of water. Basically, as we age we tend to dry out.
Because water is so critical to the function of EVERYTHING, and we get rid of water daily through urine, sweat and breathing, our bodies have very elaborate methods of preserving and prioritizing water when not enough is consumed.
One top priority is the blood, and the body does what it can to maintain a proper viscosity and composition of blood elements. So, if the person is dehydrated, water will be selectively taken from areas that are less important for survival, such as the joints (ouch!) and the lumbar disks, particularly L5, the bottom-most disk (double ouch!)
The disks use their water volume as hydraulic support for weight of the upper body. Less hydrated disks are more prone to flatten or degenerate, causing the ligaments that interconnect the vertebrae to slacken, possibly resulting in instability and low-back pain. But at least the blood is in good shape.
If there isn’t enough water for adequate blood volume, some capillary beds (tiniest blood vessels) may close so that the blood doesn’t have to go as far. Closed capillaries cause resistance in the arterial system, so more pressure is needed to pump the blood throughout the body.
Exercise helps reduce blood pressure because it keeps capillary beds open. One can ask if diuretics (water pills) are really a good idea for treating high blood pressure! Getting rid of more water is most likely to make the problem worse over time as the body adjusts to a further dehydration.
Usually initially one’s blood pressure is reduced on diuretics, but eventually most wind up on a different form of blood pressure medication such as beta blockers or ace inhibitors when the diuretics “stop working”, due to further constriction of the arterial system to cope with chronic worsening dehydration.
Perhaps the initial treatment should be to drink adequate water so that the capillary beds can re-open and blood pressure can return to normal. According to Dr. Batmanghelidj in his book Your Body’s Many Cries For Water, if there are heart failure issues, water intake should be increased gradually over time to allow the body to slowly reduce its drive for sodium retention, and increase its ability to produce urine.
Most of us can increase the amount of water we drink more quickly. Drink half your bodyweight in pounds, in ounces of pure water each day (0.033kg in litres.) Measure it so you know you are getting enough.
Caffeinated beverages, and alcohol do not count as they are diuretics and will cause you to lose water, so drink an extra cup of water for each cup of those beverages you consume. Drink up and feel better!