We all need water to survive. Water accounts for 50 to 70% of our whole body weight and it is important for most bodily functions. Any deficit in normal body water, like through sickness, heat stress, dehydration or exercise, can make you feel rotten. First, we feel thirsty and fatigued and we may develop a mild headache. This immediately gives way to mental and physical decline as well as grumpiness.
We continually lose water through our urine, breath, skin, and feces. Most healthy people regulate the water level of their body remarkably well through drinking and eating and they are guided by thirst and appetite. But this is more difficult for sick people, the elderly, infants, athletes and those with strenuous physical occupations, especially when they are under the heat of the sun.
What happens when you dehydrate?
By the time you feel thirsty, your body is already dehydrated. Our thirst mechanism lags behind our actual level of hydration. A study showed that as little as 1% of dehydration can negatively affect your attention, mood, memory and even your motor coordination. The data in humans are lacking and is contradictory, but it appears that brain tissue fluid decreases with dehydration, and this reduces the brain volume and it temporarily affects cell function.
As you lose the water in your body without replacing it, your blood becomes more concentrated and this can trigger your kidneys to retain water. The result is you urinate less, and this will eventually lead to kidney problems.
The thicker and more concentrated your blood becomes, the harder it is for your cardiovascular system to compensate by increasing your heart rate in order to maintain your blood pressure. When your dehydrated body is pushed, like when you exercise or you are faced with heat stress, the risk of exhaustion or collapse increases. This can cause you to faint when you stand up too quickly.
Less water can also hamper your body's attempts at regulating temperature, which can cause hyperthermia. Hyperthermia is a body temperature that is greatly above the normal body temperature.
At a cellular level, the shrinkage happens as water is effectively borrowed to mainta in other stores, like the blood. The brain senses this and it triggers an increased sensation of thirst.
How much water should you drink?
Your water needs change due to different factors like metabolism, diet, body composition, climate and even clothing. The first official recommendation about water intake was made as recently as 2004. The adequate water intake for adult men and women is 3.7 and 2.7 liters of water per day, respectively. This is according to the Institute of Medicine.
Around 80% of total daily water should be obtained from any beverage like caffeinated drinks, water and alcohol, and the remaining 20% from food. But of course, this is just a rough guide, there are other tips on how you can stay hydrated.
The most important thing that you need to do is to track your body weight and stay within 1% of your normal baseline. You can work out your baseline by averaging your weight on three consecutive mornings.
You also need to monitor your urine. You should be urinating regularly, around three to four times per day, and it should be a pale straw or light yellow color without a strong odor. If you urinate less frequently, and it comes out in a darker color and it is too pungent, then you must drink more water.
Read also: Thirst: How the Body Regulates It
