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Kavouras Discusses Dehydration, Benefits of Water Consumption

Short Talks From the Hill, a podcast from the University of Arkansas, highlights research and scholarly work across campus. Each segment features a university researcher discussing his or her work.

DeLani Bartlette: Hello and welcome to Short Talks From the Hill, a podcast from University of Arkansas. My name is DeLani Bartlette. In this episode, Stavros Kavouras, professor in the College of Education and Health Professions and director of the Hydration Science Lab, discusses his research on hydration. Hi Dr. Kavouras.

Stavros Kavouras: Hi. Thank you for the invitation; it’s my pleasure and my honor to be here.

Stavros Kavouras

DB: Thank you for coming. So, can you talk a little bit about how important hydration is, and, of course, the age-old question: how much water should we be drinking?

SK: Hydration is very important. I think this is a way to make people understand how important it is. It’s our bodies made out of water, mainly out of water. About 60% of our body’s water, and actually when you look at kids and newborns, that percentage is even higher. We cannot survive without water for more than maybe five, six, seven, eight days, versus we can make it with water and without anything else, we can make it for probably a month and a half, maybe two.

DB: Wow, that is that is pretty important! So how much water should we be drinking per day?

SK: This is a great question, and actually, there is not a perfect answer, and the reason is, our daily needs for water vary depending on some important factors. So one of them is the weather, how warm is the weather. So down here in Arkansas when it’s warm and humid, especially during the summer months, we might have significantly higher water needs. The other factor, which is also very important, is physical activity. So the answer would be completely different if you talk to somebody who has completely sedentary lifestyle in a cold environment, versus if you compared to one of our football players that they exercise in the heat for multiple hours, that their water needs could be three, four or even five times higher. Unfortunately the hydration science and the research on hydration has been ignored for many decades, and as a response, we haven’t really established dietary guidelines for water to the extent that we have for almost every other nutrients. So to really answer your question, based on those guidelines that we have right now for adults, males and females, for adults the total water intake it’s about 3.7 liters, which is close to a gallon of water, and for females it’s a little bit less; it’s 2.6 liters per day. One clarification that I would like to make is that amount includes what’s called “total water intake,” so it includes water that we don’t see sometimes because it is within the food. So it’s all the water included in every solid food and in every beverage, so this is a total volume. And this seems to be a sufficient amount for most people. But in general when you drink I would say somewhere around probably eight to ten glasses of water.

DB: So at this Hydration Science Lab, you’re actually studying it, as opposed to just looking at what the averages are of what people drink. So can you talk a little bit about some of the more recent discoveries that you’ve made about hydration?

SK: We are studying some specific things that that I believe that they are groundbreaking in the association between water intake and health. More specifically, we have recently published studies showing that low water intake – and I’m not talking about people that they don’t drink any water, just people that they just drink small amount of water – they can have negative effect in their ability to regulate blood glucose. And you know that problems with blood glucose regulation, or to use the layman’s term of what it means or diabetes or pre-diabetes. So what we found is that if you are not drinking enough water, your body has more difficulty to regulate glucose.

DB: I know that there are a lot of people who think that things that they drink can actually have a negative effect on their hydration. I’ve heard that alcohol or coffee can actually cause you to become dehydrated. Is that true?

SK: For alcohol it is absolutely true. When we drink, when we drink alcoholic beverages, that suppresses, actually, the anti-diuretic hormone, and that will increase the risk. So by drinking alcohol, we have greater urinary output. And whoever hangs out in the bars often, they know that the line in the bathroom is usually very long, and it’s a response not because you drink a lot of fluids, but also the alcohol has diuretic effect. Some of the side effects that you have like headache, etc., are associated with dehydration. Coffee’s a little bit different, actually. Coffee could have a diuretic effect in a higher level of consumption. We also published a study, actually, just a few months ago, where we examined the effect of caffeine in the form of coffee, so coffee ingestion and how coffee intake affects –  acutely at least –  your water balance. And we found that if you take large amount of coffee, coffee that will have about 400 milligrams of caffeine, approximately, seems to have a diuretic effect. But if you have low consumption of coffee, then it would not have the diuretic effect. So in practical terms, if you have one or two cups of coffees, you’re probably okay. While then if you do have four or more, then you’re getting into the diuretic effect of caffeine, at least acutely.

DB: That’s good to know. And I see that you studied with the researcher who came up with the chart that can show how your urine can tell us a little bit about your hydration. Is that really something that people can use on a day-to-day basis to monitor if they are well hydrated or not?

SK: Yes, this is a very good example, actually, a practical example, of how can people take home what we study in a laboratory and try to apply it in day-to-day situations. I did my PhD, actually, with Professor Lawrence Armstrong from University of Connecticut, who came up with this idea based on simple observations. You know when you do hydration studies, most of the time we’ll collect urine samples, and he had observed the darker urine seems to be associated with more dehydrated people, or dehydrated samples. So indeed he did the first validation study; we did another study that we published last year here in the University of Arkansas, where we validated this color chart in children, and we found that when your urine is concentrated, when your urine looks dark, it’s a very good indication that you need to drink more water. So relatively clear-looking urine should be a good indication that you’re in a good hydration state.

DB: So on the other side of the equation, is it possible to drink too much water?

SK: The answer is yes, you could be, but it is extremely difficult to really do something. You have to really try very hard to drink that much that could be dangerous or it could be bad for you. Your body has this magnificent ability to regulate water, so if you drink too much, your body will get rid of the extra water. In some very rare occasions, if you drink that much, you can potentially exceed your maximum kidneys’ ability to excrete extra water and you can develop what is called water intoxication, or the scientific term is “dilutional hyponatremia,” which is quite difficult to develop. I think the concern in my mind is that majority of people do not drink as much as they have to, and to be more specific, we have national data from the United States and we know that more than 50 percent of children have very concentrated urine, indicating that they’re under-hydrated. We have data that they show that one in four children in America never drink water. We know that three-quarters of American kids consume more than one soft drink per day, with all the implications to body weight regulation, diabetes, tooth decay, etc. When we look at the data with older adults, that they are more vulnerable to dehydration, we know that older adults do not get thirsty, and when they get thirsty, they drink less. So there are a lot of implications, at least in those cases, and younger people and in older adults, as far as water intake and health, and I think all it takes is to be a little bit more careful with how much you drink, and I think you can use simple tricks that you can you can do to improve your hydration – have water with you, like if especially if you work in an office, just make sure you have a glass of water with you so you can see it and it’s easier to drink. And if you don’t go to the bathroom for too many hours then this is a thought that you can use that you probably need to drink more water.

DB: So thank you for coming and sharing all this with us.

SK: Thank you, my pleasure.

Matt McGowan: Music for Short Talks From the Hill was written and performed by Ben Harris, guitar instructor at the University of Arkansas. For more information and additional podcasts go to kuaf.com or research frontiers.uark.edu, the home of research news at the University of Arkansas.

About The Author

A former newspaper reporter, Matt McGowan writes about research in the College of Engineering, Sam M. Walton College of Business, School of Law and other areas. He is the editor of Short Talks From the Hill, a podcast of the University of Arkansas. Reach him at 479-575-4246, or dmcgowa@uark.edu.

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