Our body is composed of up to two-thirds water. The human brain is composed of 95 per cent water. Water, also helps regulate metabolism and body temperature. Dehydration can have a variety of effects on individuals including fatigue, short-term memory loss, trouble focusing on fine print, and even basic math abilities. Water plays a key role in maintaining normal body functions and in preventing disease.
Considering that water is essential in so many bodily functions, constant rehydration is crucial. For a fortunate few – most of us reading this included – water is always readily available. In fact, for these lucky few, the abundance of water around them can be disillusioning. Many misconceptions arise: the idea that we have plenty of water to spare, the thought that some forms of water are not drinkable, and the general feeling that this crucial source of life can be taken for granted. Two common water myths will be examined: the claim that we should all drink eight glasses of water a day, and the stigma of tap water.
Eight glasses a day?
You’ve heard it before: we all need to drink eight cups of water a day. If a standard glass is eight ounces, this recommendation works out to be almost two litres a day. But where does this claim actually come from? Do we really need to drink eight cups of water a day? As it turns out, the answer is no.
There is yet to be a paper that recommends eight glasses a day on the basis of sound scientific evidence. The nearest link appears to be from the book of renowned nutritionist, Fredrick Stare, which states: “How much water each day? This is usually well regulated by various physiological mechanisms, but for the average adult, somewhere around six to eight glasses per 24 hours, and this can be in the form of coffee, tea, milk, soft drinks, beer, et cetera. Fruits and vegetables are also a good source of water.”
Somehow, this afterthought has caught on, and transformed into a solid and seemingly reputable medical suggestion. The rationale of thinking that, because so much of our body is composed of water, we must drink large amounts of water, is illogical and akin to thinking that, because cars require gas to run, you need to refuel your tank every day.
So how can you tell how much water you need to drink? Some of us believe that by the time we are feeling thirsty, it is already too late – our brains have shrivelled up like raisins and lest we quickly quench our parched throats, terrible things will happen.
Nothing can be farther from the truth. While thirst can set in when plasma osmolality (concentration of non-water substances per kilogram of water) is above 294 mosmol/kgH2O, one is not dehydrated until plasma osmolality rises above 302 mosmol/kgH2O.
In addition to this, there is a notion that dark-coloured urine is an indicator of dehydration. Average urine osmolality is approximately 600 mosmol/mosmol/kgH2O; urine with this concentration is usually a moderate yellow colour. At this level of urine osmolality, plasma osmolality is much lower than the 302 mosmol/kgH2O threshold of dehydration. In conclusion, being thirsty and having yellow pee are not signs of dehydration.
But are there potential benefits to drinking more water than what the body requires to function? There are claims that water can reduce the risk of cancer, heart disease, constipation, and help one lose weight. One study done by the Department of Nutrition at Harvard University looked at the relation between the total fluid intake and risk of bladder cancer of almost 48,000 participants over a period of ten years. These fluids were not just restricted to water, and included a wide range of 22 different drinks. Researchers calculated an approximate 7 per cent decrease for every extra glass of fluid. There was a significant decrease in risk for men who drank approximately six glasses, which is still below the eight glass recommendation.
Another study from the University of Texas Medical School followed 15 healthy participants with no prior history of constipation or diarrhoea found that, although increasing fluid intake increased urination significantly, there was no discernable effect on stool. There is a plethora of scientific literature on the subject of water and its effects on human health, but overall, the claim that everyone should drink eight glasses of water a day cannot be said to have been indisputably validated, scientifically.
The question now arises: if drinking more water can be good for you, why not? When we drink water, it gets removed from our body through urine and sweat. Water also regulates the level of salt in our blood. If one drinks too much water in a relatively short period of time, the kidney will not be able to remove it quickly enough and the blood will be too diluted, and thus will contain an insufficient concentration of salt. In severe instances this can result in death. Typically, these instances are extremely rare and only often seen in elderly people with impaired kidney functions or in people who take drugs such as ecstasy that result in increased thirst and difficulty to excreting water.
In conclusion, while there is evidence that suggests there are positive benefits to drinking more water, which can come from a variety of drinks – and even from food – there is no conclusive scientific evidence that suggests we must all drink at least eight glasses of water a day.
Tapped in or bottled up?
Tap water usually carries the stigma of being a health risk and of containing harmful chemicals. However, it is debatable whether tap water really is worse than bottled water. Tap water is controlled by more rigorous standards than bottled water is, but bottled water is subjected to more advanced treatment, leading to a lower risk of contamination during the process. Test results are inconclusive and the safety of water simply depends on each specific case. The quality of tap water can vary from region to region. Rural areas and some First Nation communities are still exposed to unsafe tap water, and a filtering or boiling process of the water is necessary. Furthermore, tap water in some countries is prone to more pollution than the tap water here in Montreal. In fact, according to CBC news online, regular Canadian tap water is extremely safe to drink – except for in the regions mentioned above.
Although the tap water in Canadian cities is perfectly safe to drink, the bottled water industry is prospering and growing fast. Bottled water not only appeals to more people because of health concerns; distaste of tap water organoleptics (the characteristics that affect taste, sight, and smell) has also contributed to a predominant public preference to bottled water over tap water, thus the surge in the water bottle industry. Nevertheless, a four-year review of the water bottle industry by the Natural Resources Defense Council’s (NRDC), an estimated 25 per cent of bottled water actually contains tap water.
Sometimes this water is further treated – but other times, it is not. While most bottled water is safe to drink, in about 22 percent of the water bottles tested by NRDC, at least one sample had chemical contaminants above state health limits. Furthermore, although we spend money to buy bottled water because we think it is “healthier,” phthalates – chemicals found in the plastic – are known to mimic and disrupt healthy hormonal functions, such as testosterone. Over time, these have been shown to leech into bottled water. Water in plastic bottles containing phthalates has been suggested by studies to be exposed to chemicals seeping from the plastic cap or liner. Unfortunately, there currently exists no legal limit for phthalates in bottled water; the bottle water industry has even managed to shut down the Food and Drug Administration proposal to set a limit on these potentially harmful chemicals. Furthermore, the immense environmental impact of water bottles is just another reason to consider reaching for a glass and turning to the tap, instead of buying a bottle.