Dry as The Sahara: Exploring the Concept of Thirst

Thirst Desert

Thirst is the way our brains let us know that it’s time to stop whatever we are doing and drink a big glass of water. What is the first symptom of thirst? Most likely that bone-dry, parched sensation in your mouth. You’ll notice the change of taste, and the smell of your breath: an almost sweet yet musty exhalation due to the lack of antibacterial saliva action. Cue the throbbing headache. 

Some boast of never feeling thirsty because they are regimented with their hydration. For others, the reminder is the thirst. A pressing thirst can disorient us, making it hard to focus on much else. 

But what does it mean to be thirsty?

Is thirst a sensation?

It has been suggested that the sensation of thirst was an evolutionary mechanism to help maintain homeostasis, the optimal functioning of all our internal, physical, and chemical conditions. When this corporeal balance becomes threatened by insufficient fluids, our neural and hormonal controls take over, signaling to the kidneys and salivary glands to preserve what’s left of our water and sodium. 

Thirst is, therefore, more than a mere sensation, but rather a battle waged by our body against dehydration. 

When do we feel thirsty?

Depends on the occasion. Often when we first wake up, our mouths feel as dry as the Sahara desert and we eagerly anticipate washing it away with a glass of water. 

In fact, drinking water first thing in the morning not only satiates your thirst but also helps to flush out your stomach and balance the lymphatic system. Considering the link between hydration and mental performance, a glass of water first thing in the morning can help you feel sharp––even before your first coffee. 

Another time when we are apt to reach for some water is during meals. Thirst often feels exacerbated by spicy foods when we believe the sensation of water will cool the burn of both the tongue and throat. However, water doesn’t actually stop the fervent blaze of a chili overload––in fact, it may make things worse as it spreads capsaicin, the active component of chili peppers. However, it’s difficult to resist water’s (temporary) relief in this situation. 

Many people think that salty foods are also responsible for feelings of thirst. Rather than being a physiological thirst, however, it’s more of a psychological one. 

Since it is common knowledge that salt causes water retention, we often feel the need to supplement our bodily fluids with extra water after a big bag of salty chips. This common myth has been debunked by researchers who found salty food actually made us hungrier, but considering the tendency to mistake hunger for thirst and vice versa, it should come as no surprise. It will take a long time to unlearn the habit of believing we are thirsty after a salty meal. 

Another moment of particular thirst arrives after we’ve been exercising. The sweat you emit while exercising also instigates thirst, but a different type of thirst altogether.

The Two Types of Thirst 

Researchers have distinguished between two types of thirst in mammals. When we gorge on a bag of salty potato chips, the resulting thirst is not the same as when we get thirsty after strenuous exercise. 

The former results in an osmotic thirst, brought about when there is an elevated concentration of salts and minerals in your blood. This thirst is one for restoring balance to your internal systems. 

In contrast, the latter is a hypovolaemic thirst, induced when you lose fluids from sweating and need to recover blood volume by rehydrating as well as replenishing electrolytes and minerals. 

These two types of thirst also result in a different pattern of fluid intake: osmotic thirst can be satiated by plain water whereas hypovolaemic thirst means we should look to mineral water. 

Glass of fizzy water thirst

How does your brain know you’re thirsty?

When we have lost about ten percent of the water in our body, we begin to get a dry mouth and trouble with cognitive functioning.  

Thanks to the neurons in the lamina terminalis which are ideally located to receive word from your body’s cells that they need some water. More perceptible cues come from your mouth (parched) and your kidneys (possibly hurting, depending on how dehydrated you are). These same neurons are capable of both triggering and suppressing your thirst. 

The Mechanisms of Thirst

While the hydrating relief of a glass of water feels instantaneous, once the dry landscape of your mouth puckers with water, it takes around two hours for your body to fully absorb the water you’ve drank and the effects of hydration to crystalize

As soon as we take a gulp of water, it is registered through the throat-brain pathway. In response to the physical act of swallowing liquid, the lamina terminalis immediately signals to the neurons responsible for generating the feeling of thirst that hydration is on its way. This anticipatory reflex also prevents you from drinking more water than the body needs. 

Your brain is able to sense that water is on its way with the help of peripheral sensors systems, including taste and smell. It’s easy to forget that behind the scenes your brain is acting like a project manager for the smooth functioning of your body. 

Key Takeaways

When you’ve noticed that you’re thirsty, your body is already desperately calling out for a hit of H20. It’s jumpstarted internal processes, advising your kidneys to hold on to whatever water is leftover. Your saliva glands are also on pause. Rather than waiting for this uncomfortable sensation to take over your senses, try drinking water at regular intervals during the day. 

By Natalia Kvitkova — Jun 11, 2021
The information contained in this article is provided for educational and informational purposes only, and should not be construed as health or nutritional advice.

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