Erica Perrier is a research scientist in the hydration for health department at Danone Research. She kindly accepted our invitation to comment on people’s testimonies that we collected around the world. As for all our interviews, we first let her watch people’s testimonies and then asked her a few related questions. The video shows a selection of her answers, and you can read her full interview below.
20 Questions About Water: What is your first reaction when you see these testimonies?
Erica Perrier: I love how many people have really informed reactions on the question; honestly there was a lot of good answers in there especially from... I think it was Rachel the hairstylist, she has a lot of good information, I don't know where she's getting it but she's spot-on!
20QAW: People tend to grant water a lot of superpowers, do you know why?
E.P.: Well first of all your body is made of more water than anything else, so the average person will have about 50 to 60% of their whole-body biomasses made of water. I think because it is so elementarily part of us, people obviously tend to associate that with an importance.
That being said, scientifically, if you ask people “what are some of the main benefits of water?” the answer gets a little blurrier. People aren't exactly sure “why” but it's more of an emotional reaction like “surely it must be something good for me”.
“The primary research instruments to make connections between a behaviour and health just don’t exist for water.”
20QAW: What are the scientifically proven benefits of good hydration?
E.P.: Good hydration is extremely important. We know this of course for people who lose a lot of water and who do physical activity, for instance if you are running a marathon, if you work in a very hot environment or if you perform labour that's particularly physical. Then it's incredibly important for you to remain hydrated for two reasons.
First of all, water is how your body cools itself so if you don't have enough water to sweat your body temperature will rise and it can be dangerous. Second, water is also the main way that the body transports oxygen to your muscles so if you don't have enough water in the body those two processes are in competition.
But that only considers a really small portion of the population.
Why is water good for the general population? It gets a little trickier because the reason we know that exercise is good for you, or eating fruits and vegetables is good for you, is that all over the world there are massive population surveys that ask people about these behaviours. They look at the health outcomes and they can conclude that people who eat a lot of fruits and vegetables tend to have less cancer for instance. Most of these studies never thought to ask people about what people were drinking, and even if they did, they didn't ask about water.
So the primary research instruments that we have to make a lot of these connections between a behaviour and health just don’t exist for water. What we do have though is the possibility to look at signs that your body is working hard to hold on to water, which probably means you're not drinking enough. We can look at your urine and we can look at a hormone in the body that just basically holds on to water when you're not drinking enough.
And what we know today is that people who don't appear to be well hydrated from those markers have a higher risk of developing chronic kidney disease, diabetes and metabolic syndrome. We also know that not drinking enough is associated with cognitive and mood impairments, like anger, frustration, fatigue or confusion and that just drinking more water can reverse those symptoms.
20QAW: Does that mean that the other testimonies in the video are not true?
E.P.: No, kidney disease is actually one of the major areas of research for water and hydration right now. Kidneys are the major organ in the body that lets you hold on to water, and there is a hypothesis that if you ask it to work too hard and to hold on to water every day, then over one day, or one week or one year, that’s maybe not such a big deal, but over five, ten or twenty years you will lose your kidney function faster and that's the difference between an old person having chronic kidney disease or having a kidney that still functions well.
And for the hangover, most of the symptoms are just due to you being dehydrated so water can definitely help!
20QAW: What is the right quantity of water per day?
E.P.: If that question had a good answer I would not have a job!
Honestly that would be like saying “what is the exact right amount of protein for everybody?”: it's a different amount for each individual. And today there is not enough research to determine exactly what that amount would be as a function of your characteristics. That’s something that we're working on.
But what I can tell you is that you can look at your urine and if you're drinking enough you will use the bathroom at least 6 to 8 times per day and your urine will be pale yellow in colour. The idea is to exclude a large volume of not very concentrated urine. That suggests that you are ingesting enough water to let everything flow out properly.
“I think there is a whole cascade of social benefits that can be brought around by access to good water.”
20QAW: Why is water quality important?
E.P.: Water quality and safety are absolutely fundamental. In many countries there is no access to good quality water, and then who needs to go get it during the day? Usually it's the women and the girls, and that impacts everything from access to education, access to employment or poverty. I think there is a whole cascade of social benefits that can be brought around by access to good water.
“If we don't think to offer water to children, they will never generate a taste for it.”
20QAW: How to encourage people to adopt healthy hydration habits?
E.P.: What we eat is anchored in tradition and culture, and not always necessarily in what's good for our bodies, and particularly for children. If we don't think to offer water, they will never generate a taste for it. I think one of the major things you can do is to have it available.
For instance I don't have a bottle of water in front of me right now so I don't have a reminder to drink, but keeping a bottle or a glass of water on your desk while you’re working, offer water as first choice to your children and really creating an hydrating environment by having a source of water available is fundamentally important.
20QAW: With the population growing and the water resources partly decreasing, is it possible that our body get used to drinking less water?
E.P.: That's a very good question, and there are some populations - especially for example in the desert - that do appear to be adapted to survive on less water. Whether that's something that we can develop, I don't know and as we know, since drinking a low amount of water over time probably leads to increased risks for kidney function decline and potential metabolic disorders, it’s probably not ideal.
“Increasing water intake can cut the number of Urinary Tract Infection’s occurrences per year in half, which also means half as less antibiotics.”
20QAW: Is there something you want to add?
E.P.: There is one health benefit I of forgot about which could be interesting for you.
It’s the subject of Urinary Tract Infection (UTI). This is a very common pathology that affects about 60% of women, and one of the challenges of UTI is that every time you have one, you have to take antibiotics which of course contribute to a worldwide issue of antibiotic-resistance. Just last month, the first ever randomised good quality study was published demonstrating that for women who suffer from recurrent UTI, just increasing their water intake can cut the number of occurrences per year in half, which also means half as less antibiotics.