Did you know that a person is mostly made up of water? About 60% of the average adult’s total weight is pure water (1, 4). Most significantly, the heart is composed of 73% water, and the brain and lungs are more than 80% water (1).
And water plays a fundamental role in keeping every part of your body healthy. In particular, the demands of the brain are most significant because the neurons of which it is built are more sensitive to oxygen deprivation and level of toxins than other kinds of cells. (2). Brain activity generates much more heat than other parts of the body, making the flow of blood around the brain an essential mechanism for cooling. Brain tissue that’s overheating or deprived of oxygen and glucose as a result of inadequate blood supply, can quickly change in functionality and physical characteristics, bringing with it reduced performance and even mistakes in judgement (12).
On the other hand, recent studies have shown (13) that children who regularly drink an adequate amount of water will have higher levels of academic performance and cognitive ability.
While it’s important to understand that the brain is extremely sensitive to the level of water in blood, there are many other physical and metabolic processes in the body that are also highly affected by the level, and purity, of water intake (20). Weight control, kidney function in detoxification, regulating digestion, muscle functions, skin vitality and almost every body function is affected by water levels to some degree. And so in order for the body to stay in good shape, and the brain not to be “cooked”, it needs an adequate supply of clean, fresh water every day.
How much fluid should I drink per day?
The National Academies of Sciences, Engineering, and Medicine determined (5) that an adequate daily fluid intake is about 15.5 cups (0.97 gallons) of fluids for men and about 11.5 cups (0.71 gallons) of fluids a day for women. These recommendations cover fluids from water, other beverages and food. (About 20 percent of daily fluid intake usually comes from food and the rest from drinks.)
Some other scientists suggest a formula according to which for every kilogram of your total weight, you need to drink 33 ml. water each day (15). However, the question is still undecided because factors like body weight, ambient temperature, level of activity and many others will determine how much fluid a person needs, and also what kind of fluid. It is not enough just to start drinking liquid — you need to do it at the right time, and very importantly, with the right liquid.
The first and most important rule is to maintain the body’s water balance throughout the day — it is important to drink water all day long, starting from immediately on waking up, and about 30 minutes before each meal rather than with the food (14). With the onset of summer heat, people are recommended to drink around one-and-a-half times the recommended minimum to compensate for liquid lost through perspiration, preferably cool plain water, rather than hot drinks (18).
In the beginning, this can be difficult for many, since most people are used to drinking only when the feeling of thirst becomes noticeable. However, it would be more correct to distribute the volume evenly and not “get drunk”.
Other studies have found that starting with a glass of water in the morning has a good effect on general health (6). This helps to improve vitality and regulate weight. Lemon and other citrus fruit can also be added to water. This approach will not only bring flavoring diversity, but also make the water more beneficial (7).
Experts have found that water intake should be cool or at least not above room temperature, but ice-cold liquid negatively affects the metabolism and can cause obesity. In one study (8) researchers found that changing the water temperature affected the sweating response of the participants after exercise and how much water they drank. The optimal water temperature in the study was 16°C (60.8°F), which is the temperature of cool tap water.
It is important to remember: you need to drink not only when you are thirsty. Get used to drinking not because you feel a need to, but because your body needs you to.
Children are a separate subject. They are at greater risk of dehydration than adults (13, 16), and also tend to forget to drink. The daily amount of water that a child needs depends on factors such as age, weight and sex. According to recommendations (9), both boys and girls 4 to 8 years old should drink around 7 cups (0.26 gallons) per day. Girls 9 to 13 years old should drink 9 cups (around 0.34 gallons) and boys 10 cups (0.4 gallons) — same goes for adolescent girls. Adolescent boys should be drinking 14 cups, or half a gallon. Boys need to drink more than girls because of their greater muscle mass. Physical activity and hot, humid weather increase the need for drinking. Watch out for the sweating of children: a child who sweats a lot, needs more water (17).
What kind of water should I drink?
Experts recommend drinking purified water, enriched with minerals (19) and preferably not from plastic bottles. Plastic drinking bottles contain many chemicals (10), that can leach into the bottled water, especially when exposed to heat or when the bottle is old. Different types of plastic can release chemicals that can pose a threat to the human body. The composition of plastic includes carcinogenic and other substances such as bisphenol-A and phthalates, some of which interfere with hormones in the body, as well as compounds the dangers of which are still poorly understood.
To always have clean water in your house, the optimal solution is to only drink purified fresh cool water. For any other source it is best to install cleaning filters.
Bodily health, most importantly of the brain, is highly dependent on maintaining a steady and adequate intake of water. The purity of the water is another important aspect, both in taking-in essential minerals and in keeping-out toxic substances that can seep in to the source, such as when stored in plastic bottles or transported in deteriorating pipes. The temperature of the water when being drunk is also important, with clear benefits for cool, pure water. And as important as this is for adults, it is even more vital for children!