Like many people, I tend to carry a water bottle around with me most of the time. Unlike a lot of those other people, however, I actually enjoy drinking the contents. I love water, and drinking it continually throughout the day is not a chore for me. Even more than tea and coffee (and occasionally wine and beer – I am a grad student), water is my main go-to liquid. If you’re a guest in my home (and weren’t able to think of an excuse to get out of it) there’s a very good chance that the only beverage I’ll have to offer you is cold water (filtered or tap). You will also not be able to locate any water “enhancements” such as Crystal Light or Kool-Aid to appease your palate. If you’re lucky I may have ice cubes.
I know that many people do not share my love of plain, ordinary water. And yet they continue to dutifully chug back bottle after seemingly awful (judging on facial expressions) bottle. Why? Well, it probably has something to do with the idea that as humans we are supposed to consume at least 8-8oz glasses of H2O per day to maintain a healthy lifestyle. This adage has been around for a while and chances are you’ve heard it from popular media sources, parents, dietitians, and possibly even a doctor or two. It’s one of those things – you just know you’re supposed to do it. So people are regularly trying to consume 1 893ml (2qt, ½ gal(US), 4 pints, 1.9leters or 1892cm3) of water each and every day.
And it has to be water. Caffeinated beverages don’t count because they act as diuretics. Same goes for alcohol. Water used and found in food doesn’t really count either. In addition to keeping you hydrated, drinking 8 glasses of water is purported to aid in all kinds of ailments. Adequate water intake has been indicated in the prevention of kidney stones, headaches, coronary diseases, urogenital cancers (bladder, ureter, kidney, renal pelvis, prostate, testicular), colon and breast cancer. It will help you lose weight, improve your skin tone, and boost your cognitive performance. In short, water is a wonder drug!
The best part of all this? It’s a myth. An untruth. Medical propaganda, or whatever. There is no actual tested scientific proof that you need to consume at least 2L of water a day to be healthy. So where exactly did it come from?
Valtin (2002) conducted an extensive review of the available literature and found a 1974 passage that might be the origin (or one of them). The quote states that the average adult should consume 6 to 8 glasses of liquid per 24 hours. It also states, however, that this can be from coffee, tea, milk, soft drinks, etc., and points out that fruit and vegetables are also good sources of water. There is also the possibility that the “8×8” rule originated much earlier in a 1945 report from the Food and Nutrition Board of the National Research Council. They suggested that most adults require about 2.5L of water daily, but that the majority of this will be contained in food. Apparently the latter part of this recommendation got lost…
Peer reviewed studies have indeed shown that caffeinated drinks, and to a lesser extent mild alcoholic ones, can and should count towards a daily fluid intake amount. Given the amount of these beverages consumed by the “average” healthy adult, plus the amount of water contained in solid foods, it is unlikely that most people need to observe the 8×8 rule. It seems more probable that if you consume 2-4 glasses of water a day, in addition to other liquids, you are probably adequately hydrated.
But what about all those alleged benefits of drinking copious amounts of water? Some research has shown that individuals who drink larger quantities of water may reduce their risk of certain types of urogential cancers and heart disease. These results, however, display clear gender biases and could only represent correlations and not true causal relationships between the disease and water intake alone. The fact that increased water intake is often associated with changes towards a healthier lifestyle in general should be taken into account.
So how much water should you be drinking? Well it really depends on your lifestyle. If you aren’t out running marathons every day and you eat a well balanced diet that includes fruits and vegetables, you should probably aim to drink 2-4 glasses of water a day, in addition to other beverages. The more active you are, the more you should drink. If you’re thirsty, also drink. If you hate water, try low sugar fruit drinks or increase solid fruit and veg in your diet. But don’t feel like you have to balance all that Coke-zero with equal amounts of H2O.