Sadly, the majority of us are chronically dehydrated, without even realising it.
By the time you feel thirsty your body is already dehydrated; ironically, our thirst mechanism lags behind our actual level of hydration. Humans frequently may lose up to 2% of their body weight as water before the thirst mechanism is activated. In addition, a lot of people not only ignore thirst instinct instinct, but suppress it throughout the day. Once we ignore that feeling of thirst, our body's thirst signal, we are telling our bodies that water isn't available. The body responds by diminishing that thirst signal to conserve energy, and then holds on to the limited reserves of water already in our body. We should all definitely try to learn to be more aware of thirst signals and what they're telling us. But, I guess simply expecting thirst to guide us 100% of the time in our busy life is a little bit idealistic.
What’s really happening to the body, when we are dehydrated ?
The water that leaves the body, as exhaled air, sweat, or urine, is ultimately extracted from blood plasma. As the blood becomes more concentrated, the hypothalamus releases antidiuretic hormone, which signals the kidneys to limit the amount of water lost in the urine, effectively diluting the blood plasma. Once the urine flow is decreased, the kidneys are unable to eliminate all the waste product substances. They remain trapped in the body, and their accumulation in the blood rises. Chronic dehydration can also contribute to the formation of kidney stones and urinary tract infections, both of which can lead to kidney damage if not treated.
There are two important additional effects resulting from water loss.
First, decreased blood volume triggers a decrease in blood pressure. It can lead to fainting or dizziness, when you stand up quickly. But human complex body mechanisms are designed to compensate and recover from such homeostasis deviations, at least in the short term. So how does the cardiovascular system respond to maintain the blood pressure? It will accelerate the pulse rate. A signal will ultimately travel to the heart to increase its rate and/or strength of contractions. For some people, it may even cause palpitations and irregular heartbeats.
Second, as a response to decreased blood volume, dehydration may also increase the blood pressure through vasoconstriction, especially in peripheral extremities, such as fingers and toes. Again, it’s a natural mechanism to protect vital organs.
The flow of blood to the extremities will be reduced and thereby the blood supply will increase just to the core of the body.
Less water also restrains the body’s attempts at regulating temperature, in some situations which can cause hyperthermia (a body temperature greatly above normal).
When you're dehydrated, you don't have enough water inside to sweat any out, which means your built-in cooling mechanism will not function as well. It’s especially relevant for those exercising or exposed to hot conditions. The heat stays trapped in your body, and your core temperature continues to rise, which may result in heat stress.
At a cellular level, 'shrinkage' occurs as water is effectively borrowed from cells to maintain other stores, such as the blood. The plasma volume is maintained more or less constant at the expense of the tissue fluids.
And don’t forget, the dehydration will cause electrolyte disbalance within the body. For example, when the loss of the water is disproportionately greater than loss of electrolytes, water will flow from cells to extracellular fluid (blood) to increase its volume to normal. Electrolytes including sodium, potassium and other ions transmit the electrical impulses that control body actions, especially in the heart and brain. That’s why dehydration is dangerous for these two vital organs.
Increased plasma viscosity is actually a recognised risk factor for myocardial infarction and has been shown to increase with dehydration.
Research shows that as little as 1 percent dehydration negatively affects your mood, attention, memory and motor coordination. Data in humans is lacking, but it appears that brain tissue fluid decreases with dehydration, thus reducing brain volume and temporarily affecting cell function. Dehydration has been linked to headache and cognitive impairment.
By the way, a chronic decrease in blood supply to the skin will result in dry and wrinkled skin.
On the other hand, overhydration is also real, but much less common. Drinking too much water rarely causes overhydration if the pituitary gland, kidneys, liver, and heart are functioning normally, making excess water easily excreted. But in some circumstances it might be a problem. For example, athletes, who drink excessive water to avoid dehydration can develop overhydration. The result is too much water and not enough sodium. Drinking water in excess without replacing electrolytes can be harmful, occasionally even in healthy people. Certain drugs, such as some antidepressants, can also cause overhydration in susceptible people.
While you are probably about to pour yourself a glass of water now, remember, hydration is not just about the amount of liquids you consume, but also how well your body tissues absorb it.
Movement is absolutely essential for improving hydration. The optimum delivery of water to our cells is enhanced through regular movement. Of course, blood and lymph transport liquids through our body. But you might be surprised to hear that it’s the body’s connective tissue called fascia, a web-like network covering everything inside the body, also moves water and conducts electricity throughout our body. When our fascia is tight, hard and stagnant, hydration has a hard time moving through the body.
So, stay hydrated and move your body :)