• Helen Phillips

Water, Water Everywhere ... so Why don't I drink?


We all know that drinking water is important to our health and wellbeing, so why don't we satiate our thirst?

If we're hungry, we have no problems digging into the cookie jar, but won't turn on the tap for water when we're thirsty!

Why is being hydrated so important?

Well, you're practically an ocean ... or if not an ocean, then a pond! Your body is composed of about 50% water. Water is the primary building blocks for cells, it adds strength to muscles, moisturises skin, helps regulates your internal temperature and transports nutrients and waste products around the body.

Water is critical to life!

Sweating is the way your body regulates it's temperature. Your body internal temperature needs to be maintained around 37-38C, and if the temperature rises to high, or falls too low, then critical to life body functions are impaired. You sweat to reduce your internal body temperature.

Sweating is absolutely critical when you exercise. Exercise creates heat in the body, and that heat needs to be dissipated otherwise your internal core temperature will rise to dangerous levels.

So what happens when you sweat?

When your body detects that its internal temperature is getting too hot, water is carried to the surface of the body. Sweat is then produced from the sweat glands onto the surface of the skin. The water in sweat then evaporates, which has a cooling effect on the skin. The cooled skin cools the blood at the skins surface and this in turn cools the body.

Everyone's sweat rate is different and it's also influenced by external temperature, humidity as well as the intensity and duration of the exercise you've been performing as well as your body size and composition.

So what happens when I exercise?

When you exercise your body produces heat and you'll start to sweat to cool the body. As you continue to exercise, and sweat more, your body will start to lose water, reducing the volume of water in the blood. As the amount of water in the blood decreases the blood becomes thicker and it becomes harder for the heart to pump blood around the body. Your heart works harder, so your heart rate goes up and exercise becomes more of an effort.

So if you're dehydrated doing exercise it'll feel much harder and your performance will be impaired

Losing just 2% of fluid can lead to mild dehydration. You'll feel thirsty, your skin will be flushed, your urine will be dark in colour and you might experience fatigue and dizziness. Losing further fluid can be dangerous, with 5% fluid loss having much more serious health consequences.

So how much water should I drink?

It's important to stay hydrated during the day and to make sure you're well hydrated before you start exercising. You need to be drinking about 2 - 2.5 litres of fluid each day, which can be water, soft drinks or tea and coffee. Drink a little and often, and before you're thirsty, as thirst is a sign that you're already dehydrated! I keep a big bottle of water with me at all times, on my desk and in my car, and take small sips through the day.

When you're exercising drink to thirst and then make sure you replenish the fluids you've lost after you've finished working out.

What about lost salt?

When you sweat you also lose salts, which appear as white stains on your clothes. These salts, such as sodium chloride, play an important role in your body, so it's also important to maintain the right balance of them in your body, otherwise body functions can be impaired.

If you're working out hard and sweating a lot, and especially if you're running a long distance on a hot day, it's important to replenish the salts lost from your sweat. Isotonic sports drinks and some energy gels contain salts, so are ideal to help replenish salts lost from sweating. If you're training for less than 2 hours you shouldn't need to top up your salts during exercise, but if you're running for more than 2 hours, it's hot and humid and your sweat rate is high, then you really should, to make sure you have the correct concentration of salts in your body.

What happens if my salt concentration gets out of kilter?

On a hot day, or a long run, you're sweating hard and drinking water (to maintain your fluid levels). But the more you sweat, the more salts you're losing, and if you're drinking water then the concentration of salts in your body will start to become diluted. If the concentration of salts in your body becomes too low you risk hyponatraemia. Hyponatraemia is a dangerous condition with symptoms that include nausea, fatigue and confusion. Slow marathon runners are most at risk. They often end up drinking too much water around the course, without replenishing lost salts, or just drinking too much water!

So if you're running for a long distance or a marathon race, to avoid any issues the current advice is to drink to thirst. You don't need to pick up water at each aid station, only when you need it and switch up the fluids you drink, trying an isotonic drink along the course.

If you want to learn more about nutrition for running check out my courses here