Water is the starting point for all life on earth. We all know that without it we’re dead in days. What we often don’t know, is how much we actually need to drink for our mind and body to be in their best shape – the answer isn’t as simple as many people assume. So, how much water should we drink, and why?
Thirsty may be too late
The obvious response is, “why not just drink when we get thirsty?” Thirst is the physical response our body sends out to help us regulate our water levels – following that seems eminently reasonable. Unfortunately, thirst isn’t always reliable.
As we age there is a breakdown in the relationship between our fluid regulatory system and the thirst impulse. This results in many older people drinking an insufficient amount of water, as discussed in a huge 2011 meta-study from the University of North Carolina, ‘Water, Hydration and Health’. One of the main effects of consistent dehydration, the authors note, is cellular degeneration. All of our organs have to work harder when we don’t have enough water, especially the kidneys. So, especially if you’re older, it’s essential that you’re not just relying on your body to tell you when you need water – you need to be doing that for yourself.
Effects of Dehydration
Not getting enough water might not seem like such a big deal, but it really is. Almost every single process occurring in your body at this moment relies on water to some extent. This rule even extends to how we think and feel. The University of North Carolina meta-study also noted that even mild dehydration results in decreased concentration, alertness and short-term memory. When we’re 1.5 litres of water short of the required amount we are moderately dehydrated. Moderate dehydration starts to affect our ability to recognise people and objects, arithmetic performance, visuomotor tracking, and psychomotor skills. Dehydration also causes a drop in blood volume, which in turn leads to less blood and oxygen getting to the brain. This is strongly linked to headaches. A 2015 Oxford University study found that increased water consumption leads to reduced headaches and lower overall risk of developing migraines in the long term.
The impact of hydration is particularly significant during physical activity. When we’re physically active not only does water become more essential, but we generally shed significant amounts of it through sweat. The University of North Carolina meta-study reviews studies that consistently reported that the failure to replenish water properly during exercise leads to a significant decrease in performance and an increase in perceived effort. That said, you don’t want to go overboard, either. A 2009 Yonsei University study concluded that drinking too much water can also have adverse effects on physical performance. Hypo-hydration significantly decreases our performance ability in high-intensity sports such as tennis and long distance running.
How Much, Exactly?
Unfortunately, when it comes to water consumption, it’s difficult to be exact. How much water you should drink depends on you and what you’re doing. For many years the accepted rule was eight glasses of water (2.5 litres) per day. This figure is misleading, however – it doesn’t consider water intake from food, how much is water is expended via sweat during exercise or as a result of high temperatures, and the personal requirements of the individual. All of these factors can dramatically affect the amount of water you require.
The current recommendation from the US Institute of Medicine for adults (aged 19 years and older) is around 3.7 litres for men and 2.7 litres for women. This is an overall fluid intake per day, including fruits or vegetables that contain water. Of this, men should drink around 13 cups from beverages, and women nine cups. One of the easiest ways to tell if you are on target is to look at the color of your urine. It should be clear or pale yellow. A darker yellow means you are not drinking enough water. So be proactive in making sure you get enough water – your body and your brain will thank you later!