Many people would have probably heard that everyone should drink at least eight glasses of water a day. But, experts, say that water needs vary tremendously in individuals, and are dependent on numerous factors such as activity level, geographic location and temperature.
How much water should you drink each day? It’s a simple question with no easy answer. Studies have produced varying recommendations over the years. But knowing the quantity of water to drink can be a challenge, particularly with the myriad of opinions on how much water we should be drinking every day.
In 2010, a report from The European Food Safety Authority suggested that the minimum level of water consumption should be two litres for men and 1.6 litres for women, or between eight and 10 glasses.
Even the UK’s National Health Service (NHS), through its NHS Choices website, once gave the recommendation to drink up to eight glasses of fluid a day – although it has since changed its recommendation to “plenty of water” for “quenching your thirst at any time.”
The one-size-fits-all mantras of daily water intake do seem to be retreating a little, however, or are at least now include the idea that individual’s water need varies depending on many factors like activity level, type of diet, body weight and environmental conditions.
“Water intake is a matter of balance of many things. A major factor that determines how much water we should be drinking every day is how much water is taken in and expended through breath, perspiration, urine and bowel movements,” said Professor Segun Fatunsi, a public health physician at the College of Health Sciences, Obafemi Awolowo University, Ile-Ife, Osun State.
According to him, individual differences such as level of sweating can also determine people’s daily need for water. Some people sweat more than the others. Water need is also increased during breastfeeding, as well as several disease states like vomiting and diarrhoea.
Basic minimum water requirement
The reality is that most people actually consume plenty of water each day, just not in the form of pure water. Many drinks, fruits and foods are rich in water. These foods when consumed contribute also significantly to daily total water intake.
Nevertheless, Professor Fatunsi said there is a minimum amount of water the human body needs to function well, adding that being thirsty is the body’s way of saying it needs water and how much to drink.
The thirst instinct is similar to things like breathing that nobody consciously thinks about. As with most things, the thirst mechanism in the brain is very reliable and so for majority of people, there is probably no need to worry about water intake at all.
Basically, Professor Fatunsi said, when thirsty, “your mouth will be dry; this dryness will be associated with a desire for liquids. Usually once water is depleted, there may be feeling of weakness or dizziness.”
But adequate water intake, he said may be a problem in people with a disease that prevents them recognising their need for water or deranged system that make water adjustment difficult.
But, are there health benefits to drinking at least two litres of water each day or sipping water constantly throughout the day, even when not thirsty?
Overall, drinking plenty of water is always a good regime for health, especially when combined with a healthy diet. It can prevent dehydration, a condition that can cause unclear thinking, result in mood change, cause the body to overheat, constipation, and kidney stones.
But, Professor Fatunsi said this regime is over stretched, adding “People say they do what they call water therapy and that it works for many health problems. But this could be risky, for instance in someone with water retention problems.
“That is why people need to take into consideration their health situation and needs before taking to such a therapy,” he declared.
Adequate water intake essential for live
Maintaining water balance is essential for survival and so drinking at least three litres of water, especially now in this hot season will be necessary that people sweat a lot, said Dr Bamidele Betiku a family physician at the Federal Medical Centre(FMC), Owo, Ondo State.
Dr Betiku declared that sometimes the colour of one’s urine may help guide if one is taking enough water.
He declared; “The urine should be colourless as it were. If colourless, it means you are taking enough water. If slightly yellowish and there is no case of malaria, we encourage intake of more water.”
Dr Betiku said this minimum amount of water also holds for both sick and healthy persons given that over 70 per cent of the cells of the body consists water.
“At any point in time when you are not having enough, you are starving the cells, tissue and organs in the body. So it is something that is very key.” he added.
However, water requirement of children is less than that of adults. According to him, their required water daily intake is determined by factors like body weight, age, socioeconomic status, and behavioural characteristics.
Thirst determines water need
Previously, a 2002 study published in the American Journal of Physiology also questioned the old recommendation of drinking eight glasses of water a day. After a thorough review, the researcher concluded there was inadequate evidence that healthy adults — living in temperate climates and not engaged in rigorous activities — need large amounts of water.
Following this, in February 2004, the Institute of Medicine (IOM) issued another recommendation that say healthy adults may use thirst to determine their fluid needs.
Exceptions to this rule include anyone with a medical condition requiring fluid control; athletes; and people taking part in prolonged physical activities or whose living conditions are extreme.
Fluid intake mechanism
Also, a multi-institute study led by Monash University, which revealed the mechanism that regulates fluid intake in the human body and stops us from over-drinking also challenges the popular idea of drinking eight glasses of water a day for health.
The 2016 study showed that a ‘swallowing inhibition’ is activated by the brain after excess liquid is consumed, helping maintain tightly calibrated volumes of water in the body.
Associate Professor Michael Farrell from the Monash Biomedicine Discovery Institute oversaw the work by University of Melbourne PhD student Pascal Saker as part of collaboration with several Melbourne institutes.
“If we just do what our body demands us to, we’ll probably get it right – just drink according to thirst rather than an elaborate schedule,” Farrell said.
The researchers asked participants to rate the amount of effort required to gulp water under two conditions; following exercise when they were thirsty and later after they were persuaded to drink an excess amount of water. In fact, they found a three-fold increase in effort after over-drinking.
According to Associate Professor Farrell: “for the first time we found effort-full swallowing after drinking excess water which meant they were having to overcome some sort of resistance.”
The study, ‘Over drinking results in the emergence of swallowing inhibition: an fMRI study,’ is published online in the Proceedings of the National Academy of Sciences.