Forget the 8 glasses of water a day rule, according to these experts | Radio Canada

You’ve probably heard that drinking eight glasses of water a day is essential, or that you should drink more when you’re sick.

But how much water does a person really need?

There are many myths about hydration, but for most healthy adults, your body will tell you when it’s time to drink, says Dr. Jane Thornton, a sports medicine doctor and former Olympic rower based in London, Utah. Ontario.

“Essentially, we should drink to thirst. It doesn’t always work, but it’s good advice for most of us,” Thornton told CBC show host Dr. Brian Goldman. The dose.

She says factors like extreme heat, cold, age and duration of exercise all play a role in when and how much a person should drink.

Experts say there are some simple guidelines to follow to make sure you’re well hydrated, even in winter.

“[For] most of us don’t need to over complicate things,” said Stephen Cheung, a professor in the department of kinesiology at Brock University.

Do I need eight glasses of water a day?

The short answer is no.

The researchers said in a recently published study that “one size does not fit all” regarding the eight glasses a day water consumption guideline.

Researchers have found that a person’s water needs vary depending on several factors such as age, health status, gender, physical activity levels and local climate.

Most people don’t need to drink two liters of water a day because they will also get fluids from other sources like fruits and vegetables or coffee and tea.

So instead of drinking a single amount of water each day, Thornton says most people should drink when they’re thirsty.

“There is no magic number,” she says.

Cheung says one of the biggest myths around hydration is that you have to constantly drink.

“There are a few exceptions, but for the most part, your thirst is a wonderful tool,” he says. “That’s more than enough to really get you drinking enough day-to-day.”

Young children and infants are the exceptions — they often aren’t able to recognize the feeling of thirst, Cheung says. Older people may also have trouble recognizing when they are thirsty, as they may have a reduced feeling of thirst.

How do I know if I’m dehydrated?

Signs of dehydration can be mild at first, with people often having trouble concentrating, headaches or irritability, says Thornton.

Darker urine, dizziness and fatigue are often more serious signs of dehydration. She says organ failure is one of the most extreme signs.

“But most of us will never get there. That’s not going to happen on a daily basis,” Thornton points out.

And there are certain medications, like certain antidepressants, that can increase a person’s risk of dehydration, Thornton added.

It’s important to stay hydrated because fluids help regulate body temperature, maintain joint lubrication, prevent infections and provide nutrients to keep organs functioning, says Emily Campbell, a Toronto-based registered dietitian. who helps people with kidney disease.

Should I drink only water?

Generally, water is the best liquid for hydrating the body, says Campbell.

“We can use things like lemon or lime to flavor our drinks, but on a day-to-day basis choosing these drinks without sugar is important,” she adds.

When training, Thornton suggests sticking to water for the first hour. After that, she suggests replacing those electrolytes with either a sports drink or food.

“You’re basically looking at electrolyte replacement [of] minerals such as sodium, calcium, potassium, chloride, phosphate and magnesium,” explains the Olympic athlete.

“[Electrolytes] help balance the amount of water in the body and…they can also help remove waste from cells.”

She says people can also fill up on food, citing bananas as a good source of potassium and watermelon as a source of potassium and magnesium.

Experts say those with a viral illness like a cold or the flu should also watch their water intake and may want to turn to a sports drink to get more carbs into their diet when they’re low on carbs. ‘appetite.

Should I hydrate during exercise?

Cheung, who has researched heat stress and its effects on the body, says the biggest myth around dehydration is that as soon as you sweat, you need to replace that water.

“The body can tolerate dehydration and can tolerate a decent amount,” he says.

He mentions marathoners or ultra-distance runners who lose weight during a race but can still perform at a high level.

“It’s not, ‘Oh, I have to drink like every 15 minutes or as soon as I start sweating, I better back up the liquids,'” he says.

He and Thornton agree that for the average person’s hour-long workout, there’s often no need to worry about huge fluid losses.

“Most people will be able to regulate themselves and drink enough when they return from exercise,” says Cheung.

He adds that there are two main factors that will affect your rate of dehydration: environmental conditions like high temperatures and exercise intensity.

“Let’s say you’re running at the same speed on a cold day…in Edmonton. You will still sweat, but you won’t sweat as much as if you were here in southern Ontario in the middle of summer where it’s very hot and humid,” Cheung says.

“Your sweat rate – therefore your dehydration rate – and potentially the amount of fluids you need to drink during and after exercise will differ depending on environmental conditions.”

If people want to get a better idea of ​​how much water is lost during a workout, Cheung and Thornton suggest weighing themselves before and after exercise.

“If you lose a pound, you’ll need to replace it with a liter of water,” says Thornton, noting that fluid loss will change depending on environmental conditions and exercise duration.

What does the body do when it is too hydrated?

Water intoxication or overhydration can be fatal, but experts say it’s rare.

Cheung says the human body is very good at “regulating your fluid balance,” both when you’re dehydrated and hyperhydrated.

“It’s very difficult to overhydrate, to be above your normal water balance, because your renal system – your kidneys – are so good at regulating your water balance that you’ll just go to the bathroom and urinate,” says -he. , adding that there are no major health benefits to being hyper-hydrated.