Can drinking water (or not drinking enough) affect your sleep?

Drinking water is essential for overall health. Water makes up up to 60% of the human body and is involved in many body functions, from cell growth to waste elimination to digestion. And yes, water can also affect sleep.

Proper hydration is essential for your body to function as it should, and not just during the day. In fact, some studies show that dehydration can have a negative effect on sleep.

However, drinking too much water before bed can also interfere with sleep. In fact, you won't sleep well at night if your bladder forces you to get up to go to the toilet.

What science says about hydration and sleep

Research on the relationship between water and sleep is limited. But the data available so far suggests a relationship between the two, with shorter sleep periods associated with lower hydration status.

In a large study⁽¹⁾ A cross-sectional study published in the journal Sleep in February 2019 showed that in a group of more than 20,000 American and Chinese adults, those who reported sleeping less than 6 hours on average each night had a greater likelihood of not drinking enough water (measured by… urine route). samples), compared to those who slept 8 hours or more each night. (Researchers studied this association because sleeping too little or too long was previously linked to kidney problems.)

On the other hand, a small study⁽²⁾ The study published in the Journal of Sleep Research in February 2018 found that dehydration did not affect the quantity or quality of sleep in 12 healthy young adults, although the study authors noted that more research is needed to determine the relationship between the two.

Other research has found that a hormone the body produces, vasopressin, helps prevent dehydration during sleep by increasing water absorption in the kidneys later in the sleep cycle (so you don't become dehydrated even if you don't drink). Water at night,” says one article⁽³⁾ Published in StatPearls August 2020 Vasopressin secretion increases towards the end of sleep to help regulate hydration levels at a time when water consumption is not possible and water loss via breathing increases. In other words, getting too little sleep can actually help cause dehydration.

Can dehydration affect sleep?

We now know that dehydration can cause the following symptoms, which can indirectly disrupt sleep:

• Muscle spasms Dehydration can lead to muscle cramps, which may make it difficult to sleep or wake a person in the middle of the night. Remember, muscle mass is made up of 76% water, as the study showed⁽⁴⁾ Published August 2019 in Nutrients;
• Muscle cramps Muscle cramps are another symptom of dehydration, which can sometimes lead to painful tension in the leg or foot muscles, which can wake a person in the middle of the night;
• headache : Headaches and migraines can make it difficult to fall asleep and achieve deep sleep;
• Night thirst A thirsty person may wake up in the middle of the night or early in the morning;
• Dry mouth : Dry mouth can also cause discomfort which can make it difficult to sleep.

Can drinking too much water disrupt sleep?

It is actually possible that drinking too much water before bed disrupts sleep. If you drink too much water in the evening, you risk disrupting your sleep because you may need to go to the bathroom to urinate in the middle of the night. There's even a medical term for it (nocturia) which can be a big problem for those who suffer from insomnia after bathroom trips.

For your information, according to two studies (one on dogs⁽⁵⁾ The other is for 14 adult men⁽⁶⁾), the kidneys filter more blood when a person is lying on their stomach, which fills the bladder more quickly and increases urine flow, as opposed to lying on their back.

When should you drink?

If you're looking to improve your sleep, you should drink water during the day and try to reduce your fluid intake later in the day, especially right before bed. It is recommended to drink water throughout the day, before, during and after meals.

It has long been thought that drinking with meals can dilute stomach acid, which can hinder digestion. However, we now know that the body is able to adapt its secretions to match the texture of the meal.⁽⁷⁾.

Another misconception about not drinking during meals is that liquids increase the rate at which food is expelled from the stomach, which reduces the time the meal comes into contact with stomach acid and digestive enzymes, leading to poor digestion. This was refuted by a study⁽⁸⁾ After analyzing gastric emptying and noting that although liquids pass through the digestive system more quickly than solids, they have no effect on how quickly solid foods are digested.

It is recommended to avoid drinking liquids at least an hour before bed. However, if you tend to have an overactive bladder or suffer from urinary incontinence, it is best to avoid drinking fluids two to three hours before bed. If you feel thirsty during the night, it is recommended that you only drink small sips as needed: “So, if you turn off the lights at 11pm, only drink small sips at 9pm.”

Aside from water consumption, it is also important to consider other factors that affect hydration throughout the day. Coffee consumption and the amount of sweat you sweat can dehydrate your body and deprive it of essential minerals. However, eating foods with a high water content (fruits and vegetables) can help you stay hydrated.

Other factors that can affect sleep and hydration

There are other factors that can affect hydration and its effect on sleep:

1. sNight scents : If you sweat a lot at night, you may have a significant amount of “unconscious water loss.”⁽⁹⁾ (loss of body fluids that cannot be easily measured), which can contribute to dehydration, according to previous research⁽¹⁰⁾. If you tend to sweat at night, it's a good idea to make arrangements to make your sleeping environment cooler, such as setting your thermostat to a temperature that's comfortable for you at bedtime, which will likely be cooler than your daytime temperature. According to the Sleep Foundation, the ideal bedroom temperature for most people is around 18°C, although it can range between 18°C ​​and 20°C. For some people, depending on the local climate, the ideal temperature may be slightly higher;
2. Mouth breathing : People who breathe through their mouths may also experience water loss during the night. According to a study⁽¹¹⁾People who breathe a lot through their mouth expel 42% more water than those who breathe through their nose;
3. Caffeine consumption : Caffeine can act as a mild diuretic (not to mention its stimulating effect), which may delay your ability to get deep, restful sleep. Therefore, it is recommended to stop consuming caffeine 6 hours before going to sleep.
4. Alcohol consumption Like caffeine, excessive alcohol intake can have a diuretic effect and disrupt the sleep cycle, leading to poor overall sleep quality. So try to limit alcohol consumption to just one drink per evening. The study found that this is especially important as you get older, because the risk of dehydration is higher with alcohol consumption as you get older.⁽¹²⁾ Published July 2017 in Nutrients.

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