There is a lot of debate about the benefits of drinking water, with questions like how much should we be drinking and is bottled mineral water better than tap water. What are the myths and what are the facts? Perhaps a drop or two of common sense is required together with some evidence based facts. One thing is absolutely crystal clear and that is water is essential for life. Water contributes to the maintenance of normal physical functions, normal cognitive functions and normal thermoregulation.
If you’ve ever had severe dehydration, you’ll know first hand, the symptoms of not having enough water. Dehydration is classified as mild, moderate or severe and just 2% dehydration will have an impact on cognitive performance such as short term memory, arithmetic efficiency, motor speed and attention.
Lets start with how much water we should be drinking per day and remember, even though we may not be drinking glasses of water directly, we are still getting water in our foods. The normal daily turnover of water, without considering perspiration, is about 4% of total body weight in adults and 15% in infants. In a 70Kg adult, this equates to 2.8 litres per day. In a 7Kg infant, this equates to 1 litre a day.
The European Food Safety Authority (EFSA) recommends a daily intake of 2.5 litres of water for men and 2 litres for women through food and drink consumption.
EFSA suggests that 70-80% of this daily water intake should come from drinks. The UK’s National Health Service (NHS) recommends that women should drink eight 200ml glasses per day and men should drink ten 200ml glasses of fluid per day. This equates to 1.6 litres for women and 2 litres for men per day. There is a little bit of difference in these recommendations but they are in the same ballpark.
So if we are looking at drinking approximately 2 and 2.5 litres of water a day, and this will vary depending on physical activity etc, does this have to be water or do other drinks contribute to this? Yes, all drinks will contain water, but clearly, drinking fizzy drinks loaded with sugar and additives is not going to be beneficial to your health. Beer contains lots of water but drinking two litres of beer will contribute to dehydration because alcohol is a diuretic which means that it makes the body get rid of water. It does this by suppressing ‘vasopressin’ which is the body’s anti-diuretic hormone (ADH). The bottom line here is that you’ll be spending more time in the toilet as you increase your alcohol consumption! This leads to dehydration and contributes to the almighty headache in the morning. Getting your quota of water from coffee may not be such a good idea either because coffee is also a diuretic. So drinking plenty of pure, filtered water is the best way to go.
How do we know when we are dehydrated? You might think that thirst is the body’s natural way of telling you to drink more. You would be right about this, however, this signal often arrives when you are already experiencing mild dehydration or a loss of water equivalent to 1% of your bodyweight. By this point, you may experiencing other symptoms of dehydration such as tiredness and headache. A good way to measure if we are getting enough water and whether or not we are dehydrated is to monitor the colour of our urine. It doesn’t sound pleasant but it is the best way available to us. Dr Lawerence Armstrong published the first validated urine colour chart in 1994.
This 8-colour scale includes colours from pale yellow, the colour of straw, (number 1) to brownish green colour (number 8). The chart is an easy way to monitor your hydration status and if your urine colour matches numbers 1-3 on the chart you are well hydrated. However, if your urine colour matches number 7 or darker you are probably dehydrated and need to drink more water!
When exercising, particularly in hot weather, it is important to be appropriately hydrated before commencing exercise in order to avoid dehydration and also getting cramp. However, it is important to avoid drinking too much water during exercise. After training for many years, particularly in gyms with no air conditioning in the hot summer months, I have found that sipping water at regular intervals throughout a workout is optimum.
In the next article, we’ll take a look at look at whether it is best to drink pure, filtered water, bottled water or plain old tap water.
Sports & fitness nutritionist, researcher and author on a mission to improve the human condition. Focusing on evidence-based and outcome-based nutrition, training, mindset & environment