Water is essential for daily functioning and health, and we can only survive a few days without it. Yet we constantly lose water through sweat, urination and even evaporation when we 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 signalling we need to have a drink. This basic physiological mechanism is controlled mainly by part of the brain’s “control centre”, 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 our bodies) 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 our 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 our 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 our 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 litres) 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 colour: 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. 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, PhD 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.

No, you’re not imagining it. People really are more likely to poo in the morning, shortly after breakfast. Researchers have actually studied this.

But why mornings? What if you tend to poo later in the day? And is it worth training yourself to be a morning pooper?

To understand what makes us poo when we do, we need to consider a range of factors including our body clock, gut muscles and what we have for breakfast.

Here’s what the science says.

So morning poos are real?

In a UK study from the early 1990s, researchers asked nearly 2,000 men and women in Bristol about their bowel habits.

The most common time to poo was in the early morning. The peak time was 7-8am for men and about an hour later for women. The researchers speculated that the earlier time for men was because they woke up earlier for work.

About a decade later, a Chinese study found a similar pattern. Some 77% of the almost 2,500 participants said they did a poo in the morning.

But why the morning?

There are a few reasons. The first involves our circadian rhythm – our 24-hour internal clock that helps regulate bodily processes, such as digestion.

For healthy people, our internal clock means the muscular contractions in our colon follow a distinct rhythm.

There’s minimal activity in the night. The deeper and more restful our sleep, the fewer of these muscle contractions we have. It’s one reason why we don’t tend to poo in our sleep.

But there’s increasing activity during the day. Contractions in our colon are most active in the morning after waking up and after any meal.

One particular type of colon contraction partly controlled by our internal clock are known as “mass movements”. These are powerful contractions that push poo down to the rectum to prepare for the poo to be expelled from the body, but don’t always result in a bowel movement. In healthy people, these contractions occur a few times a day. They are more frequent in the morning than in the evening, and after meals.

Breakfast is also a trigger for us to poo. When we eat and drink our stomach stretches, which triggers the “gastrocolic reflex”. This reflex stimulates the colon to forcefully contract and can lead you to push existing poo in the colon out of the body. We know the gastrocolic reflex is strongest in the morning. So that explains why breakfast can be such a powerful trigger for a bowel motion.

Then there’s our morning coffee. This is a very powerful stimulant of contractions in the sigmoid colon (the last part of the colon before the rectum) and of the rectum itself. This leads to a bowel motion.

How important are morning poos?

Large international surveys show the vast majority of people will poo between three times a day and three times a week.

This still leaves a lot of people who don’t have regular bowel habits, are regular but poo at different frequencies, or who don’t always poo in the morning.

So if you’re healthy, it’s much more important that your bowel habits are comfortable and regular for you. Bowel motions do not have to occur once a day in the morning.

Morning poos are also not a good thing for everyone. Some people with irritable bowel syndrome feel the urgent need to poo in the morning – often several times after getting up, during and after breakfast. This can be quite distressing. It appears this early-morning rush to poo is due to overstimulation of colon contractions in the morning.

Can you train yourself to be regular?

Yes, for example, to help treat constipation using the gastrocolic reflex. Children and elderly people with constipation can use the toilet immediately after eating breakfast to relieve symptoms. And for adults with constipation, drinking coffee regularly can help stimulate the gut, particularly in the morning.

A disturbed circadian rhythm can also lead to irregular bowel motions and people more likely to poo in the evenings. So better sleep habits can not only help people get a better night’s sleep, it can help them get into a more regular bowel routine.

Regular physical activity and avoiding sitting down a lot are also important in stimulating bowel movements, particularly in people with constipation.

We know stress can contribute to irregular bowel habits. So minimising stress and focusing on relaxation can help bowel habits become more regular.

Fibre from fruits and vegetables also helps make bowel motions more regular.

Finally, ensuring adequate hydration helps minimise the chance of developing constipation, and helps make bowel motions more regular.

Monitoring your bowel habits

Most of us consider pooing in the morning to be regular. But there’s a wide variation in normal so don’t be concerned if your poos don’t follow this pattern. It’s more important your poos are comfortable and regular for you.

If there’s a major change in the regularity of your bowel habits that’s concerning you, see your GP. The reason might be as simple as a change in diet or starting a new medication.

But sometimes this can signify an important change in the health of your gut. So your GP may need to arrange further investigations, which could include blood tests or imaging.

Vincent Ho, Associate Professor and clinical academic gastroenterologist, Western Sydney University

This article is republished from The Conversation under a Creative Commons license. Read the original article.