Your Thirsty Brain: Hydrate Your Way To Better Cognitive Performance

Picture a parched man, desperate for water in the desert. Most studies on dehydration are performed in extreme conditions, such as endurance events or high heat. Or, they are conducted on niche populations - top athletes or soldiers, for example. For this topic on cognitive performance, we specifically focused on mild changes in hydration, in everyday settings. What we found is eye-opening.

Small changes, big effects

Do you know why confusion and disorientation are two pronounced symptoms of dehydration? It turns out that our brains are really sensitive to water. When hydration levels fall by just a bit, loss of concentration occurs early on. You may not even notice, but if you performed a cognitive test, you’d see the drop-off clearly. And, if hydration status worsens, other cognitive symptoms follow, including poor judgment and impaired decision-making.

The emotional aspects of dehydration are just as intriguing. A 2012 study, published in The Journal Of Nutrition, found that a tiny 1.4% reduction in hydration negatively affected mood, perception of task difficulty and concentration. It also increased the likelihood of headaches.

When we're hydrated, our brain is better able to regulate body temperature, so we feel less fatigued and more alert. Cognitive-motor performance is affected by hydration as well. For example, reaction time declines along with hydration. And, in one study, golfers hit 12% shorter and 93% less accurately when mildly dehydrated.

Because small changes in hydration have such profound and wide-ranging effects on our brains, and because the effects can be subtle, it’s important to pay real attention to hydration, not just for athletic performance, but for daily life performance too. We generally don’t think about hydrating before an exam, or before we start work, especially work that involves thinking, but we should - it’s one of the easiest hacks to ensure we get the best results we can.

Why are our brains so sensitive to hydration?

To understand this better, it helps to appreciate three facts.

Firstly, our brains are 75% water. Your skull is filled with cerebrospinal fluid that surrounds your brain's folds and lobes. It cushions your brain from injuries and has nutrients and proteins that help keep it healthy and working.

Not only is sufficient water necessary for your brain, but the correct concentration of sodium and potassium is also required. Sodium regulates water outside your cells and potassium regulates it inside. We can’t hold onto water without enough of these minerals. So drinking plain water isn’t as helpful as one might think. Without the minerals, water is just released via urine.

Secondly, the human brain has an estimated 85 billion neurons, far more than anywhere else in the body. Neurons are nerve cells that transmit ultra-fast messages, using electrical charges. These electrical signals underlie ALL your thoughts, behaviours and perceptions of the world. Sodium and potassium ions are at the core of this electrical network, making it all function. (An ion is a molecule that carries an electrical charge, either positive or negative). Without the right balance of these ions, our brains suffer more than other organs.

Thirdly, sufficient water is needed to maintain blood volume. Blood is the transport system that brings oxygen, glucose and other nutrients to your brain. It also clears waste products from your brain. When you aren’t hydrated properly, blood volume falls a little, and the entire transport system becomes sub-optimal. Your brain is particularly dependent on glucose because it doesn’t have its own stores. It relies heavily on the continuous supply from the bloodstream. When this is off by just a little, your brain knows.

Magnesium - the unsung hero

All this electrical activity in our brains requires energy. Sodium and potassium are necessary to conduct the electrical charges, but what makes the sodium and potassium move in and out of cells? If you’re a geek, you may be able to guess – It’s called ATP. Adenosine triphosphate (ATP) powers every process, in every cell, in our bodies.

ATP is biological energy. Just as money is the currency of an economy, ATP is the currency of energy. But, few people know that ATP must bind to magnesium in order to work. Magnesium is the third leg of the brain’s mineral ion network. Sodium and potassium are like the electrical cord to your toaster. ATP + magnesium is the plug that turns it on. Insufficient magnesium equals insufficient energy.

Magnesium does lots of other things too. It is known as the relaxation mineral. It helps to calm the brain, just as it helps to relax muscles. That’s why good sleep remedies contain magnesium. 

Older, wiser, dehydrated

Older adults should pay particular attention to hydration. Our thirst sensation decreases as we age, making the elderly more vulnerable to mild dehydration. A 2020 study found a staggering 38% of more than 30,000 older adults at least mildly dehydrated.

Combined with a generally higher risk of cognitive decline, it’s imperative for our seniors to drink enough water and get sufficient minerals. Prolonged dehydration causes brain cells to shrink in size and mass, a condition common in many elderly who have been dehydrated for years. Lack of mental clarity, sometimes referred to as “brain fog”, is the last thing they need, especially when the remedy is so simple.

Balance is also a big deal for older folks. A quarter of senior citizens in the USA report falling each year. And falls, for people over 65, can precipitate a deterioration in health that is, all too often, fatal. Falls account for 95% of hip fractures, according to Dr Peter Attia, an impeccable doctor, scientist and ageing specialist. And hip fractures in the elderly are associated with high mortality rates within a year of the fall.

What does falling have to do with hydration? Well, our cognitive-motor function controls balance. And, as explained earlier, mild dehydration impairs cognitive-motor functioning. Furthermore, the loss of blood volume caused by under-hydration hinders the delivery of oxygen, which can cause dizziness, lightheadedness and, you guessed it, loss of balance. It can even cause temporary loss of consciousness.

Putting all these factors together, a compelling case is made for people over 65 to deliberately drink water with enough electrolyte minerals, and perhaps set reminders to overcome the blunted thirst problem. It has been shown that anything that helps water taste better has a big effect on adherence among seniors. Ideally, these agents, usually flavours and sweeteners, should be of the healthier variety.

To sum it up 

The brain isn’t the first organ we think of when we consider hydration. However, people in the low carb world and those who practice intermittent fasting know the link between electrolytes and cognitive symptoms like fatigue, brain fog and headaches. We hope this article pulls together some other interesting pieces of the hydration-cognition-emotion puzzle. If ever there was a reason to hydrate properly as part of everyday life, this is it, and particular attention should be given to our senior citizens. Start first thing in the morning, along with your coffee, not an hour or two later. Give your magnificent brain the best chance to be its best.