How to stay hydrated

Don’t wait for thirst to hit: keep fluids up throughout the day for optimal mind and body function.

Written by David Cameron-Smith
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Humble water, fresh from the tap, is a quaint throwback to schoolyard days and summer holidays spent at grandparents’ houses. Jars recycled as glasses and water from the tap have given way to trendy, new age drinks, providing an ever increasing range of osmolytes, nutrients and brain boosters. No matter how hip hydration has become, it’s still the humble partnership of two hydrogen atoms and a single oxygen atom in a unique union that makes water what water is and does.

What is thirst?

Thirst is a hardwired response triggered by decreasing blood volume. This signals the brain stem to activate a range of hormones and nerves to help try to reduce any further losses.

A dry mouth and an overwhelming need to quench the thirst are the most obvious effects. Thirst might also be accompanied by a headache and feelings of tiredness.

Unfortunately, these biological responses come after water has already been lost from the body. The signs of increasing thirst are not apparent until the body has lost at least 1-2% of total body weight. This can be well in excess of one litre of body water already lost. By the time you start to feel thirsty, nerves and muscles, including the heart are already compromised.

This is heightened as you get older. For many older people, feeling thirsty follows even greater levels of dehydration. This can be dangerous – every summer, heat stress proves too much for some of our senior citizens.

"Unfortunately, these biological responses come after water has already been lost from the body."

How to stay hydrated

There are no universal rules of how much and when to drink. The rate of fluid loss from the body varies greatly from one day to the next. The big influences are heat and exertion.

Sweating is an effective way to cool the body, but it comes with the loss of body water. Even if the sweat is not dripping from your forehead, a modest workout will generate a measurable amount of sweat. The harder you go, the more you sweat, increasing the speed of dehydration.

Remaining adequately hydrated is about preparation and adaptation. Ensure you leave the house well hydrated and prepared. Bringing a bottle of water with you is a great idea.

For regular consumers of coffee or tea, the caffeine levels do not usually trigger greater fluid loss. However these beverages are not great ways to hydrate. Mostly served hot, a steaming cuppa may even increase your core temperature and when sipped slowly, does little to restore body fluid levels. Cold teas and coffees are often as sugar-laden as standard soft drinks.

"Don’t rely on your thirst to tell you when you need to drink more water. Instead be prepared, drink up early and stay hydrated throughout the day."

On the opposite side of the equation are the ‘rules’ of drinking eight glasses or ‘at least’ two litres of water each day. For most people, on most days, this amount will have you rushing off to the toilet. There is no evidence that it helps flush out toxins, gives you smoother skin or helps with concentration. But at these levels, there are no indications that it will do you any harm. For most of us, most of the time, water does just fine. It is true that the body loses salts, and that combinations of dextrose sugars help increase water absorption, but the effects are small.

Don’t rely on your thirst to tell you when you need to drink more water. Instead be prepared, drink up early and stay hydrated throughout the day. Before, during and after any exercise, remember to drink. Importantly, if you can avoid strenuous activity or exercise in the heat of the day, do so.

Heat exhaustion and dehydration can be dangerous, impairing your judgement and compromising the functions of vital organs. It’s time to rediscover water and the joy of drinking from a glass.

Think you could do with drinking more water? When you download the Medibank Live Better App you can join our 'Stay Hydrated' challenge and earn points by simply topping up your water intake each day.

Download the Medibank Live Better App to set your health goals, join a challenge, and start earning points today.

Written by David Cameron-Smith

Professor David Cameron-Smith is a health expert and the current Chair in Nutrition at the Liggins Institute, University of Auckland.

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