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Nutrition: Good and Bad Hydration

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To keep your body full of energy and performing at its best, good hydration is essentialWe all need around two litres of fluid a day to keep our bodies properly hydrated. Water is the medium in which most of body processes take place, and makes up about two thirds of body weight. Right now 50% of the population is poorly hydrated. We lose water via breathing, sweat and urine.

The functions of Water

  • Regulates Body Temperature
  • Lubricates joints
  • Assists digestion & carries nutrients throughout the body
  • Diffusion of gases insuring a moist environment (breathing)
  • Waste products leave the body through water
  • Gives each cell in the body proper form

The recommended daily two litres of fluid should come from water, plain or flavoured. We also get approximately half a litre from food eaten each day, about a quarter of daily needs, mostly from fruit and vegetables. Of course, alternatives to water do tend to have more calories, so it makes sense to get at least some of our daily fluid needs from water. Also, some studies have indicated that drinking plenty of water is beneficial to the immune system; good for the skin; alleviates constipation and can reduce the risk of kidney stones.

Dehydration can make you feel tired and lethargic, and will decrease your capacity for exercise. Extra fluid is needed in hot weather and when you exercise. For each hour of exercise you should drink an extra litre of fluid. If you have an illness that is causing sickness, diarrhoea or sweating, you will need to up your fluid intake to make up for the extra loss.

Hyponatremia, also called water intoxication, is generally the result of drinking excessive amounts of plain water which causes a low concentration of sodium in the blood. Once a rare occurrence at sporting events, it is becoming more prevalent as participation increases and more novice exercisers are entering endurance events.

Hydration and Exercise

Proper hydration is helpful for achieving the best performance in elite athletes. Adequate fluid intake is also helpful for recreational exercisers to exercise at their best. There have been recommendations about how much water or sports drinks are needed and over the years athletes were advised to drink much more water than we now know is necessary. New Guidelines on nutrient recommendations were published by the Institute of Medicine of the National Academies (external link).

They state that the vast majority of healthy people adequately meet their daily hydration needs by letting thirst be their guide. They don't provide specifics, such as the number of glasses of water per day, because fluid needs can be met through a variety of sources besides drinking water alone.
The group makes special recommendations for athletes (external link) in the area of water, sodium and potassium.

The International Marathon Medical Director's Association also revised guidelines regarding hydration for athletes in May 2006. They recommend drinking a sports drink when exercising thirty minutes or more. They also state that during a marathon, it's best if runners listen to their body and drink when they feel they need to.

For many exercisers water intoxication is a very real and very serious complication from drinking too much water. The numbers of triathlon and marathon participants, who develop symptoms of water intoxication, continue to grow as more and more novice exercisers have entered these events.

So what is the right amount of fluid to drink? Well, that all depends, and in fact, it may not be that important to try to figure it out.

The longer and more intensely you exercise, the more important it is to replace lost fluids. And for an elite athlete, a loss of two percent of body weight in fluid has been linked to a drop in blood volume. This makes the heart work harder in order to move blood through the bloodstream. For elite athletes this decrease can result in a slight decrease in performance. Dehydration in athletes may also lead to fatigue, poor performance, decreased coordination and muscle cramping. The American College Of Sports Medicine provides guidelines for athletes regarding proper hydration and fluid replacement.

Hydration Guidelines

If you feel that you need some sort of guideline to determine how much you should be drinking, use the following as a starting point.
Drink no more than 1 glass of water every twenty minutes. You can also weigh yourself before and after you exercise to get a sense of how much fluid you typically lose. One kilo is equivalent to approximately 750ml of fluid.

Sports Drinks

Sports drinks can be helpful to athletes who are exercising at a high intensity for 60-90 minutes or more. It's necessary to replace losses of sodium, potassium and other electrolytes during exercise. Keep in mind that under normal situations most exercisers are unlikely to deplete these minerals during regular training. If, however, you find yourself exercising in extreme conditions or for long times (an Ironman or ultra-marathon) consider adding a sports drink with electrolytes.
Hyponatremia may occur during longer events when athletes drink excessive amounts of plain water.

The Pee Test

Thirst is not a good indicator of dehydration. Use the pee test to assess how hydrated you are.

Target Dehydration Severe Dehydration

When you are well hydrated, your pee should be the colour of pale straw.
This relates to colours I or 2 on the chart.