A jug of water with lemon in and glasses on a table.

The effects of dehydration on your motivation and mood

Posted by for Wellbeing

Not drinking enough water can impact your brain function and mood. In her latest Head Strong column, psychologist Kimberley Wilson explains the link between dehydration and mood. 

Hey there. How are you feeling? A little tired? Maybe a tad thirsty? If this is you then I’m here to tell you that the two might be related and to explain how your hydration status affects how you think and feel.

Your brain is 80% water. That’s a higher proportion than the rest of your body, which comes in at around 60%. Water in the brain helps supply oxygen, eliminate waste, and supports overall brain structure. This makes your brain particularly sensitive to water loss, with dehydration changing the brain’s shape and function in often dramatic ways.

To test the effects of dehydration on the brain researchers invited volunteers into the lab, have them sweat on a stationary bike, before scanning their brains. What they found is a loss of brain volume (or shrinkage). In fact, studies suggest that the shrinking that occurs during dehydration can sometimes be mistaken for brain damage. Thankfully, this returns to normal when hydration is restored. Despite being easily reversable, dehydration does get in the way of normal brain activity.

Although it might not always feel like it, your brain is always, always working hard. Because of all that power, the brain is the hungriest organ in your body, accounting for around 20% of your total energy consumption when your body is at rest. The energy, nutrients and oxygen required to produce this high work rate are all supplied by the bloodstream but when you become dehydrated, especially during exercise, the amount of blood flowing to and through your brain decreases. Incredibly, your brain is able to compensate for this reduced blood flow for a while. 

When dehydrated, your brain cells work harder to keep up. However, this results in increased perceived effort (it feels more difficult to do the same amount of work when you are dehydrated compared to when you are not) and increased fatigue. That is to say, everything feels harder and you become tired more quickly.

A woman drinking from a bottle of water while smiling on her bike in a park.
Drinking enough water is important for energy levels, according to Kimberley.

After a while the reduced energy and nutrient availability starts to impact your brain’s performance. Studies have shown that at 2-3% dehydration (relative to body weight) people suffer from poorer concentration and impaired hand-eye coordination, which is definitely not what you need in the middle of a workout. Its negative effect on memory is also not a great look mid-presentation. As if that wasn’t enough, dehydration lowers your motivation and increases the production of stress hormones leaving you feeling headachy and miserable.

Talking of headaches, alcohol triggers the body to release water, which is why you feel like your head’s been stuck in a vice after a big night out. And while caffeine can increase urination, in moderate amounts and for regular drinkers it shouldn’t be too dehydrating. However, if you are reaching for a cup of coffee it might be a sign either that you are thirsty or in need of a mental boost, both of which might be better served by having a glass of water. 

I recommend having a small glass of water while you are waiting for the kettle to boil. That way you cover all your bases. When working with clients on good neuro-nutrition, I advise against too many sugar-sweetened drinks as studies show they can harm the brain. Yep, in terms of hydration your best bet is plain water.

Plain water may seem a little boring but there are ways to make it more enjoyable, such as adding herbs like mint or rosemary or slices of cucumber and slices of fruit to make your H2O more enjoyable. 

It’s also worth changing the way you look at water. Instead of seeing drinking water as a chore, focus on how much your mood, concentration and overall brain function are going to benefit from the improved hydration. Think of it as one of the simplest ways of taking care of yourself. Or, to put it another way, having a glass of water is an act of self-care

We all have different hydration needs depending on our body size, activity level, and environmental conditions so the best way to tell what is the right amount for you is by checking the colour of your pee. A lighter, straw-like colour is good.

How to stay hydrated

Make it routine 

Make having a glass of water part of your morning routine. A glass of water first thing will help to replenish water lost overnight. Remember to hydrate before your workout, as well as during and after.

Make it tasty 

Herbs, citrus peel, sliced fruit and fruity or herbal tea bags all make water more interesting. Clients who have struggled to drink plain water often find sparkling water easier to manage. And many people find chilled water ‘tastes’ better too.

Anchor it 

The easiest way to develop a new habit is to link it to something that you already do. So if you regularly drink three cups of tea a day, make it a habit to have a glass of water first.

Make it obvious 

Your brain responds to visual cues so it can be helpful to have a refillable water bottle on your desk to keep reminding yourself to drink up.

Want simple and nutritious recipes? Make sure you check out the rest of our meal ideas in the SWTC library.

Images: Getty / Pexels 

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Kimberley Wilson

Chartered psychologist Kimberley Wilson is our Head Strong columnist, one of our resident experts from the Strong Women Collective and author of How to Build a Healthy Brain. She’s passionate about caring for our mental health through evidence-based nutrition and psychological therapy – and loves discussing how you can train your mindset to become stronger in body and mind.

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