Understanding Hydration


Understanding Hydration

Your body is made up of between 65 to 75 percent water so a ten stone (140 pound/64 kilogram) person’s body contains around 42 to 48 litres of water! It’s no wonder then that virtually every nutritional expert places a high value on hydration, rehydration and avoiding dehydration.

Water is a number of functions in your body including:

  • Temperature regulation through sweating
  • Movement of chemicals around your body
  • Medium for chemical reactions
  • Lubrication of digestive tract
  • Elimination of waste materials and toxins
  • Integral part of all muscles
  • Provides a carrier medium for blood cells – known as plasma

Water is the most essential part of your diet. You can live for quite a long time without food as even the leanest person has a significant supply of body fat but, as we cannot store much water and it is essential for virtually every reaction that occurs in your body, you won’t live more than a few days without water to drink.

Staying Hydrated
As it is water your body needs, it is water you should drink but there are numerous opinions about how much water you need. The most common hydration recommendation is six to eight tall glasses of water a day; the equivalent of around two litres. Interestingly, this figure has absolutely no scientific basis and is not the result of any studies, medical journals or statistical research. It’s simply a figure that was proposed back in 1945 by the American Nutrition and Food Board that was adopted by just about everyone thereafter. That is not to say that these figures are wrong but only that two litres is an arbitrary number based on one organization’s opinion as opposed to scientific fact.

Rather than focus on the amount that your body MAY need, it is better to focus on what your body actually DOES need. The best determinant of your water needs are your thirst and your urine colour and output.

Thirst should be  our best hydration indicator. Our caveman ancestors’ probably only used thirst to govern their water drinking habits. If you were thirsty, you needed to drink. Simple! The problem now is that,  because modern man often slakes his thirst with sweetened, calorie dense beverages, thirst and hunger signals can become confused. In other words, you might feel hungry but, in reality, you are actually thirsty but your brain gets the signals all turned around! This was not a problem for our non-sugary drinking ancestors. Subsequently, thirst has become a less accurate indicator of hydration. Because of this lack of thirst sensitivity, it is better to drink enough water to avoid thirst in the first place.

Urine Colour and Output
Other than your first urination of the day, most experts agree that your urine should be relatively clear, fairly copious and also odourless. Dark, smelly and infrequent urination can be a sign of dehydration and the less than rosy odour suggests a build up of undiluted toxins and waste-products.

By avoiding thirst and making sure most of your urinations are a light straw-like colour and neutral smelling, you can be confident that your body as all the water it needs to maintain healthy metabolic and thermoregulatory functions.

Mild dehydration is common. A hard workout, too much coffee or alcohol, too little water or hot weather can all result in less than optimal water levels in your body. This is not a serious problem if this is a short term or infrequent occurrence but regular and/or long term dehydration can cause numerous performance and medical related problems.

Signs of Dehydration – in approximate order of onset and severity

  • Dry mouth (sometimes referred to as “cotton mouth”)
  • Reduced urine output
  • Dark, odious urine
  • Headache
  • Muscle cramps
  • Fatigue
  • Cessation of sweating
  • Hot, dry skin
  • Elevated heart rate
  • Confusion
  • Elevated core temperature
  • Heart palpitations
  • Unconsciousness
  • Kidney failure
  • Coma
  • Death

Too Much of a Good Thing?
While water is essential for life, too much water can actually be harmful to your health. Although very rare, some people have suffered from a condition called hyponatraemia, also known as water intoxication. This condition can manifest if you drink very large volumes of water, for example during a long distance running event where you consume significantly more water than you are losing by over taking on water at each and every feed station. This results in a dangerous dilution of essential minerals, collectively called electrolytes; specifically sodium. Sodium is essential for muscle contractions, regulating inter and extracellular fluid levels and pressure as well as controlling heart rate and rhythm. A significant enough sodium dilution can even prove to be fatal. Needless to say, this is a very rare occurrence and is usually the result of an underlying medical condition combined with an extreme excess in water or sports drink consumption.

Sports Drinks
No discussion of hydration would be complete without mentioning sports drinks. With so many on the market and so much advertorial information telling you what drink you should consume when, it can be very hard to choose a sports drink that is ideally suited to your needs.

The first question to ask yourself is, however,  do you really need a sports drink? If you are exercising for 60 minutes or less, are exercising for weight loss and have eaten properly in the hours leading up to your workout, I would suggest that plain water is more suited to your purposes. If, on the other hand, you are not eaten properly before training, are going to be working for 60 minutes or more and are not trying to burn fat during your workout, a sports drink is an acceptable way to stay hydrated. There are three main types of sports drinks:

  • Hypotonic
    With a very low amount of carbohydrate, a hypotonic drink is mostly about hydration and offers very little in the way of fuel. That being said, ingesting carbohydrates can suppress fat burning so water is the better choice if that is your exercise goal
  • Isotonic
    Containing around 6 grams of carbohydrate per 100 millilitres of water, isotonic drinks are the most common sports drinks. Usually engineered to provide a mix of slow, medium and fast acting sugars for energy plus essential electrolytes, an isotonic drink provides fuel and hydrating fluids in equal measure. Isotonic drinks are ideal for long workouts where a drop in blood glucose or muscle glycogen levels would result in decreased performance. However, the carbohydrate content and extra calories in these types of products would negate most of the benefits of a fat-burning workout.
  • Hypertonic
    Ten plus grams of sugar per 100 millilitres of water means that hypertonic drinks are more food than fluid. The high level of sugar may actually interfere with water absorption so these drinks are not ideal for helping you stay well-hydrated. If you chose to use a hypertonic drink, you should also consume plenty of plain water to make sure that you rehydrate as well as refuel.

The bottom line is that your body needs copious amounts of water to function properly and while soft drinks, coffee, tea, alcoholic beverages, fruits and vegetables can all contribute to your daily fluid intake, it is water that your body needs. Avoid getting thirsty, drink as much as you need to keep your urinations frequent and mostly clear, drink plain water during most types of exercise and use sports drinks wisely and you’ll be well on your way to avoiding dehydration.