Did you know that…
Water is virtually everywhere, from soil, moisture, and ice caps to the cells inside our own bodies. Still, freshwater accounts for only 2.5% of Earth’s water and only 1% of the world’s freshwater is within reach. This is because much of it is locked away: almost two thirds of it lies frozen around the poles. However, any living organism, whether animal or plant, depends upon it as it collects, transports and distributes a life-giving ingredient: oxygen. Human adults, depending on factors like location, fat index, age or sex, are between 55 to 60% water, and at birth, human babies are 75% water.
What roles does water play in our bodies?
Among their most important functions, water molecules in our body cushion and lubricate our joints, regulate our temperature and also nourish our brain and spinal cord. Besides, whereas most of the water we contain sits in our cells and flows in our blood, other organs are also surprisingly liquid. An adult’s brain and heart are almost three quarters water, sharing the amount of moisture of a banana. Lungs are more similar to apples, as they consist of around 80% water and even seemingly dry human bones are 31% water.
Why do we still need to drink water?
Despite being essentially made of, and surrounded by water, the human body is not designed to store it. Each day, we lose between 1 to 3 liters through our sweat, urine, bowel movements and even just from breathing. This explains why we still need to drink to compensate for this fluid loss and avoid dehydration, but we also need to keep our water uptake in check to avoid overhydration as both conditions can have devastating effects on our health.
What does dehydration feel like?
At first detection of low water levels, sensory receptors in the brain’s hypothalamus signal the release of an antidiuretic hormone (ADH). When it reaches the kidneys, it creates some very special channels known as “aquaporins” that enable blood to absorb and retain more water, giving rise to concentrated dark urine. Persistent dehydration can cause notable drops in energy, mood, skin moisture and blood pressure, as well as signs of cognitive impairments: a dehydrated brain tires very rapidly and may eventually shrink owing to its lack of water.
Why are people dehydrated?
The most common cause of dehydration in people is the insufficient uptake of water, due to sanitary reasons or lifestyle. Even so, it is also possible to experience dehydration because of an adrenal dysfunction. We indeed possess two adrenal glands, located on the top of each kidney, hence their other name: suprarenal glands. Among other very important stress or sexual hormones, the adrenals are responsible for secreting aldosterone that in turn is in charge of regulating the uptake of water in the kidneys. A lowered adrenal function will disturb the electrolyte balance of the body and eventually cause dehydration by not retaining enough water and eliminating too much of it. Likewise, low-sodium (or low-salt) diets can also result in dehydration, since sodium is essential in maintaining water balance, determining plasma and blood volume for example.
What does overhydration feel like?
On the other hand, overconsuming water can result in a rarer, yet very concerning condition called hyponatremia. Because they often absorb substantial quantities of water in short amounts of time, athletes present a higher risk of overhydration. Contrary to the dehydrated brain, the over-hydrated brain slows down and even stops releasing antidiuretic hormone into the blood, and sodium electrolytes in the body become diluted, causing cells to swell. Hyponatremia can provoke headache, vomiting, and in the most extreme cases, can even lead to seizures and death.
So, how much water do we actually need to drink to stay healthy?
The traditional estimate of 8 glasses a day has been fine-tuned and nowadays, we are aware that the amount of water we need to imbibe largely depends on our weight and environment. Therefore, the recommended daily intake varies from between 2.5 to 3.7 liters for men and from 2 to 2.7 liters for women according to our health status, physical activity, or age. Eliminating clear and colorless urine is also an excellent sign of correct water intake.
Also have in mind that water within food makes up about a fifth of our daily water intake. For instance, strawberries, cucumber and broccoli are over 90% water and can replenish our fluids while providing valuable nutrients and fiber.
What water should I drink?
One out of ten people in the world cannot actually be sure that their water is clean and safe to drink due to inadequate sanitation, poor protection of drinking water sources and improper hygiene. And when water goes through its sanitation and disinfection processes it can become contaminated by chemicals like chlorine, often held responsible for pipe erosion and the subsequent release of iron, copper and lead into drinking water. Such byproducts have been linked to long-term health effects like cardiovascular and neurological diseases, cancer and miscarriage. Although point-of-use processes involve ionization, absorption and filtration, reverse osmosis (RO) systems are more efficient at purifying tap water, especially from heavy metals.
Fresh drinkable water is a scarce yet essential resource to fulfill one of the most basic of our human needs. It should be protected, saved and fairly shared. The delicate balance of water absorption and excretion is a key to optimal health. Make sure you drink enough of clean water, and that your body swimmingly manages it!