Water makes up 60% of the body and 75% of the brain. To say it is essential is an understatement; in fact just 3 days without water can be fatal.
Dehydration can impact five aspects of your mental performance:
1. Decreased reaction time
2. Decreased short term memory
3. Reduced attention span
4. Reduced accuracy in complex tasks
5. Increased fatigue
If you are not getting enough, it could be impacting on your career.
As I have discussed before creating something you can stick to is the key to success. Many sources recommend having up to 8 glasses of water a day. This is a myth dating back to a US recommendation in 1945! Not only is this far too much for most people, but is a difficult habit to keep.
1. One glass of water, as soon as you wake up
2. Eat one more portion of fruit and vegetables a day
3. One glass of water before you go to bed
4. Drink water when thirsty (sounds simple, but many reach for sugary drinks instead)
5. If you don't like 'plain' water, have a tea or coffee
Remember water doesn't just come from the tap. Meat is 50-70% water while fruit & vegetables can be 75-96% water.
Science of dehydration
Dehydration at a 2% body mass loss can impact your brain, and even 1% loss can cause your performance to decrease.
Water is required for the brain's production of neurotransmitters and hormones. A study from Kings College London showed by MRI that dehydration increases ventricular expansion and causes inefficient use of brain metabolic activity after dehydration.
Other research has identified that the effect of water consumption is dependent on the subject's thirst and the positive effects result from an 'attenuation of the central processing resources consumed by the subjective sensation of thirst that otherwise impair the execution of speeded cognitive processes'. Translated into English: you can't get on with the task at hand, as all your brain is telling you to do is 'find and drink some water'!
Not all studies have shown a beneficial impact on cognition. This study showed no effects of dehydration in healthy subjects on performance of a number of cognitive tasks. However, they observed that dehydration caused changes in subjective ratings, such as increased tiredness, and higher levels of perceived effort and concentration.
Caffeine is a diuretic and will dehydrate you? Wrong. A team from the University of Birmingham studies took 50 coffee drinkers and had half of them drink 4 cups of coffee, and the other half the equivalent of water. Their results showed that no difference of total body water or urine volume (collected up to 24 hours) was found between the two groups. Suggesting coffee contributes to your daily fluid intake.
Can you drink too much?
As with everything in life there is a consequence of having too much. If you drink too much water you can suffer from what is known as hyponatremia. To put it simply, this is when the amount of water in the blood drowns out the sodium. This is commonly found in long distance runners who try and overcompensate by drinking too much water. It can cause confusion and headaches. However, there is little evidence to show the impact of this on your cognitive performance.
Water is vital for our brains to function, and to enhance productivity. However, as water is available in most food produce, an optimal amount is much less than the '8 glasses a day' dogma.
Alleviating thirst is a key factor to reducing fatigue to maximise your mental performance.
Drink smarter. Perform Smarter
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Edmonds, C et al. Subjective thirst moderates changes in speed of responding associated with water consumption Front. Hum. Neurosci., 16 July 2013
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Smith M The use of Magnetic Resonance Imagery (MRI) in examining the effects of dehydration on brain structure and function in healthy humans