I may be showing my age but I remember the days before you could buy drinking water in convenient sized bottles in the local supermarkets, convenience stores or roadside stops. In fact, there was no such thing as bottled water, except in large dispensers in office buildings. How did we survive? I'll tell you how we survived - we drank tap water to meet our thirst. We had a glass of water that was poured directly from the tap or from a storage container in the refrigerator that was originally also filled from the kitchen tap. When we sat down to eat we had a glass of water with our meal - not soft drink, fruit juice or some other commercially sold and bottled beverage - just plain old tap water. And if we were out and about shopping or running errands what did we do? We waited until we got home and THEN had a drink of tap water.
Did anyone die back in those good old days from dehydration because they couldn't have access to water in convenient bottles every minute of the day - of course not! Did anyone die back in those good old days from dehydration because they couldn't have access to water in convenient bottles every minute of the day - of course not! No! It was accepted that you drank when you felt thirsty - if you lived in a hot climate then you felt thirstier than someone who lived in a cold climate and therefore drank more - if you exercised then you felt thirstier than someone who didn't exercise so you naturally drank more - if you ate salty foods then you felt thirstier and therefore drank more. All of these situations were controlled by a bodily function that is as scientifically controlled and precise as the most complex of physics laws... THIRST. The remarkable achievement of the sports drink and bottled water industries has been to convince recent generations that this control mechanism does not exist or is totally unreliable.
Testament to this is the fact that the global bottled water sales, according to a report in Wikipedia, have increased dramatically over the past several decades, reaching a valuation of around $60 billion and a volume of more than 115,000,000 cubic metres (3.0×1010 US gal) in 2006. U.S. sales reached around 30 billion bottles of water in 2008, a slight drop from 2007 levels. The global rate of consumption more than quadrupled between 1990 and 2005.
Spring water and purified tap water are currently the leading global sellers. By one estimate, approximately 50 billion bottles of water are consumed per annum in the U.S. and around 200 billion bottles globally. And all of this consumption is from a population that, until about the 1990's, were predominantly drinking water solely from their kitchen tap - when they felt thirsty!
The drinking guidelines provided by government and sporting bodies for both active and non-active people are finally being questioned by reputable sports medicine scientists who recognize the alarming increase in cases of exercise-associated Hyponatremia (EAH) amongst sporting event competitors. For instance, researchers found that 13% of the athletes who finished the 2002 Boston Marathon were in a clinically hyponatremic condition.
Hyponatremia is an electrolyte disturbance in which the sodium concentration in the blood is lower than normal. Normal blood sodium levels are between 135 and 145 mmol/L. Hyponatremia is defined as a serum level of less than 135 mmol/L and is considered severe when the serum level is below 125 mmol/L. If the blood sodium level is allowed to get this low there is the high likelihood the person will suffer from hyponatremic encephalopathy which is a brain dysfunction caused by the accumulation of fluid in the brain consequent to a reduced blood sodium concentration. When this condition occurs in an exercising athlete it is referred to as Exercise-Associated Hyponatremic Encephalopathy (EAHE).
Once the blood sodium concentration falls below about 128 mmol/L, affected athletes present with varying degrees of altered levels of consciousness, from mild confusion to frank coma (complete loss of consciousness), frequently associated with epileptic seizures. Other complications include noncardiogenic pulmonary edema with respiratory failure. The primary abnormality is excessive fluid accumulation in all the fluid compartments of the body-in the cells, around the cells, and in the bloodstream. But brain cells, encased as they are in a rigid skull, cannot increase their volume without causing a steep rise in the pressure inside the brain. The progressive increase in pressure inside the waterlogged brain cells interferes with their function, leading ultimately to death with the cessation of certain vital functions, in particular those of the heart and lungs.
EAHE is due to abnormal fluid retention in those who voluntarily overdrink during prolonged exercise usually lasting at least 4 hours. Abnormal sodium losses either in sweat, urine, or diarrheal fluid do not cause this condition and in fact do not contribute in any way to the seriousness of the condition.
Knowing these facts about Hyponatremia, I start hearing alarm bells when I read comments like the one below that I recently read on a Facebook post:
"Just been reminded on how important hydration is!!! Most of us are dehydrated & quite often when we think we are hungry it is really dehydration!! Me, I know I am still not drinking enough water for the amount of activity I am doing so quite often I feel tired, less able to cope, light headed & suffer from headaches, scratchy, & lacking in concentration! Plus my skin is dry, I have dark circles under my eyes, & my performance decreases!! So what is the recommended amount of water?? Read an article in a fitness magazine that suggests you should drink one litre of water per 25kgs of body weight!! So for a 65kg person that is 2.6 litres this doesn't allow for climate or activity! I am currently drinking about 2.5-3 litres a day & judging by how I feel that still isn't enough!!
If someone is experiencing all those health problems and they are drinking an amazing 2.5-3 litres of water - on top of all the water they would be consuming through their solid foods as well - then it seems more likely that rather than being dehydrated they are in fact "waterlogged" and have seriously affected the body's natural solute concentration homeostasis. Hunger can never be misinterpreted as being dehydrated - "thirst" is the unique and precise indicator that your body uses to let you know if you need to drink more water - no other physiological reflex will do that. There is no denying the fact that drinking water will take the edge off your appetite but only consuming liquids (either in the form of water itself or in foods that contain water - which is practically all foods!) will alleviate the feeling of thirst. It's probably a good idea to point out that a lot of the 'solid' foods you eat contain appreciable amounts of water also.
Vegetables and fruits are around 90 per cent water, as is milk, fruit juice and soft drinks. Cooked meats and fish are over 50 per cent water, and breads are about one-third water.
When people hear that you need to consume so many litres of water a day they forget that your body is already consuming an incredible amount of water through the foods you eat and the non-water beverages you drink. No one seems to take this into account when they are doing the calculations nor do the 'experts' who write the published articles that the public read ever refer it to.
The only symptom of dehydration is thirst, which is simply a self-correcting biological signal that ensures that healthy humans do not develop a fluid deficit sufficient to cause illness. Often it is an overwhelming sense and this thirst mechanism will ensure that all modern athletes competing in long-distance running, cycling, and triathlon events in which they have free access to all the fluid they could possibly desire cannot develop life-threatening dehydration unless they so choose. If at any time a healthy athlete does not sense thirst, the athlete is not dehydrated.
What Happens When We Get The Hydration Equation Wrong?
With the ever-increasing numbers of participants in endurance events around the world there has been intense focus on the hydration needs of these athletes.
It's interesting to note that the focus on hydration requirements has come about since the invention of commercially produced sports drinks and it's probably no coincidence that these companies provide sponsorship to the world's major sporting events. Before Gatorade was invented in 1965 the only source of fluid replacement was water and there were no guidelines on how much should be consumed. Quite to the contrary, athletes - including marathon runners - considered it was a sign of weakness if you stopped for a drink during an event.
Over the years the recommendations on how much fluid you should be consuming before, during and after an event steadily increased to the stage where sporting bodies such as the American College of Sports Medicine, the National Association of Athletic Trainers and other sports medicine groups were advising endurance athletes to drink 600 to 1200 ml/hour (20 to 40 ounces).
These figures came about through recommendations from Gatorade-sponsored studies that showed this amount of fluid replacement was necessary to maintain fluid balance in the body while exercising. Subsequent studies that were done by independent researchers were not accepted by the broader sports medicine world until decades later when the increase in Hyponatremia amongst endurance athletes became too serious to ignore.
These outdated hydration recommendations (remember "Conventional Wisdom" is quite often proven wrong!) continued to be used by ill-informed athletes and as a result there was an alarming rise in the number of people suffering from Hyponatremia in many endurance events around the world. This came to a head in the early part of this century when in 2002 it was estimated that 13% of the participants in the Boston Marathon may have suffered from Hyponatremia and there was a Hyponatremia death in both the Boston and Marine Corps Marathons.
As with the sporting community, the Military also adopted guidelines for programmed drinking to maintain performance and minimize the risk of heat casualties because they recognized that personnel, especially those in the training environment, were subjected to arduous physical activity in sometimes extreme climatic conditions.
Conclusion
Although sporting bodies and the military are now recognizing the dangerous effects over-hydrating can have on the body and are revising the fluid intake recommendations down from what used to be advised, the general non-sporting community is taking longer to get the message that the safest way to hydrate your body is to rely on the body's age old sense of thirst. DRINK TO THIRST - it can't be any simpler than that! If it's a hot day you'll feel thirstier than on a cold day so you'll drink more... if you're exercising you'll feel thirstier than if you're not, so will drink more... it's not rocket science so why are people still calculating how many ounces per kg of body weight over a period of time depending on the amount of calories you are burning and what part of the world you live in at certain seasons of the year?
The "conventional wisdom" saying of "IF YOU ARE THIRSTY THEN YOU ARE ALREADY DEHYDRATED" is the most over-used and under-researched saying of the past generation. Thirst isn't an indication that you are dehydrated but the body's way of alerting you to the fact that if you continue to do what you are doing without rehydrating then you WILL EVENTUALLY become dehydrated. Our body is smart enough to give us fair warning before any deficiencies become life threatening. Except for an extreme few people who have the rarest of genetic disorders that stop the sense of thirst from working, EVERY other person in the world gets, and recognizes, the sensation of thirst.
Every process within the body is precise and has been evolved over hundreds of thousands of years to adapt to the environment it has to live in. Maintaining homeostasis within the body's cells is a subconscious process that is so critical that it has been designed to take the conscious thought process out of it. We don't have to decide how much water to drink - our body does that for us.
Have the efforts to protect athletes from dehydration actually undone the natural protections offered by our bodies, causing hundreds of athletes to overdrink, leading not to good health and performance but to dangerous medical conditions? If this practice of overhydrating, especially in the non-active population, continued over several years, if not decades, could a biological modification eventually occur that could present the person with serious health problems due to possibly an irreversible shift in body fluid homeostasis?
This is yet another case where putting blind faith in "conventional wisdom" of the day could prove not only detrimental to peoples current health but could have serious consequences for the autonomic processes that the body relies on for good health.
