Water is essential for life. It makes up 50–80% of our body weight and dehydration as little as 2% loss of body weight can affect our health and performance. But there are many myths and misconceptions when it comes to meeting our fluid needs.
Everyone needs to drink 8 glasses of water each day.
Australian dietary guidelines suggest an average fluid intake of 8 glasses (2.1L) for women and 10 glasses (2.6L) for men. But this will vary widely from one person to the next depending on their size, environmental conditions, physical activity levels and individual metabolism. And this is total fluid not just water, although water should be our first choice.
Tea and coffee don’t count towards our fluid intake.
While tea and coffee have a mild diuretic effect, the fluid loss caused by this is much less than the amount of fluid consumed in the drink. So tea and coffee still count towards your fluid intake.
I need a sports drink to keep hydrated during exercise.
While adequate fluid intake during exercise is essential to prevent dehydration, most of us don’t need a sports drink to keep hydrated. If you’re doing long duration exercise, particularly in the heat, then a sports drink may be beneficial to help replace electrolytes lost in sweating. But for your average gym workout, water is all you need.
Thirst is a good indicator of fluid needs.
Thirst isn’t always reliable, particularly as we age. A number of studies have shown reduced thirst sensation in the elderly, which can contribute to dehydration. One of the best ways to work out if you’re hydrated is to check the colour of your urine – if it’s lightly coloured or clear, you’re drinking enough. If it’s darker yellow, you need to drink more (unless you are taking vitamin B supplements which can cause bright yellow urine).
- Vreeman & Carroll. Medical Myths. BMJ 2007;335:1288 http://www.bmj.com/content/335/7633/1288
- Valtin. “Drink at least eight glasses of water a day.” Really? Is there scientific evidence for “8 x 8”? Am J Physiol Regul Integr Comp Physiol. 2002 Nov;283(5):R993-1004.
- NHMRC: Nutrient Reference Values for Australia and New Zealand: Water.