Water is essential for daily functioning and health, and you can only survive a few days without it. Yet you constantly lose water through sweat, urination, and even evaporation when you breathe.
This is why we have evolved a way to regulate and maintain water in our bodies. Like other animals, our survival relies on a strong biological drive that tells us to find and drink water to balance fluid loss.
This is thirst — a sensation of dryness in the mouth signaling you need to have a drink. This basic physiological mechanism is controlled mainly by part of the brain’s “control center,” called the hypothalamus. The hypothalamus receives signals from various regions of the body and, in return, releases hormones that act as a messenger to signal the thirst sensation.
What is dehydration?
Staying hydrated (having enough water in your body) is important for several reasons, including:
- regulating body temperature through sweat and respiration
- lubricating joints and eyes
- preventing infections
- digesting and absorbing nutrients
- flushing out waste (via the kidneys)
- preventing constipation
- brain function (including memory and concentration)
- mood and energy levels
- physical performance and recovery from exercise
- skin health.
Dehydration occurs when your body doesn’t have enough water. Even slight drops in fluid levels have noticeable consequences, such as headaches, feeling dizzy, lethargy, and struggling to concentrate.
Chronic dehydration can pose more serious health risks, including urinary tract infections, constipation, and kidney stones.
What does the evidence say?
Despite thirst being one of the most basic biological drivers for good hydration, science suggests your feelings of thirst and subsequent fluid intake don’t always correlate with hydration levels.
For example, a recent study explored the impact of thirst on fluid intake and hydration status. Participants attended a lab in the morning and then later in the afternoon to provide markers of hydration status (such as urine, blood samples, and body weight). The relationship between levels of thirst in the morning and afternoon hydration status was negligible.
Further, thirst may be driven by environmental factors, such as access to water. For example, one study looked at whether ample access to water in a lab influenced how much people drank and how hydrated they were. The link between how thirsty they felt and how hydrated they were was weak, suggesting the availability of water influenced their fluid intake more than thirst.
Exercise can also change your thirst mechanism, though studies are limited at this stage.
Interestingly, research shows women experience thirst more strongly than men, regardless of hydration status. To understand gender differences in thirst, researchers infused men and women with fluids and then measured their thirst and how hydrated they were. They found women generally reported thirst at a lower level of fluid loss. Women have also been found to respond more to feeling thirsty by drinking more water.
Other ways to tell if you need to drink some water
While acknowledging some people will need to drink more or less, for many people, eight cups (or two liters) a day is a good amount of water to aim for.
But beyond thirst, there are many other ways to tell whether you might need to drink more water.
1. Urine color
Pale yellow urine typically indicates good hydration, while darker, concentrated urine suggests dehydration.
2. Frequency of going to the toilet
Urinating regularly (around four to six times a day) indicates good hydration. Infrequent urination can signal dehydration.
3. Skin turgor test
Gently pinching the skin (for example, on the back of the hand) and observing how quickly the skin returns to its normal position can help assess hydration. A slow return may indicate dehydration.
4. Mouth and lips
A dry mouth or cracked lips can be early signs of dehydration.
5. Headaches and fatigue
Frequent headaches, dizziness, or unexplained fatigue can be signs of inadequate hydration.
6. Sweating
In physically active people, monitoring how much they sweat during activity can help estimate fluid loss and hydration needs. Higher levels of sweat may predispose a person to dehydration if they are unable to replace the fluid lost through water intake.
These indicators, used together, provide a more comprehensive picture of hydration without solely depending on the sensation of thirst.
Of course, if you do feel thirsty, it’s still a good idea to drink some water.
Lauren Ball, Professor of Community Health and Wellbeing, The University of Queensland and Kiara Too, Ph.D. candidate, School of Human Movement and Nutrition Sciences, The University of Queensland
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Follow us on X, Facebook, or Pinterest
