{"id":25157,"date":"2021-04-21T02:01:00","date_gmt":"2021-04-21T02:01:00","guid":{"rendered":"https:\/\/www.lifeandnews.com\/articles\/?p=25157"},"modified":"2021-04-22T12:37:57","modified_gmt":"2021-04-22T12:37:57","slug":"do-you-really-need-8-glasses-of-water-a-day-an-exercise-scientist-explains-why-your-kidneys-say-no","status":"publish","type":"post","link":"https:\/\/www.lifeandnews.com\/articles\/do-you-really-need-8-glasses-of-water-a-day-an-exercise-scientist-explains-why-your-kidneys-say-no\/","title":{"rendered":"Do you really need 8 glasses of water a day? An exercise scientist explains why your kidneys say &#8216;no&#8217;"},"content":{"rendered":"\n<p><a href=\"https:\/\/theconversation.com\/profiles\/tamara-hew-butler-519686\">Tamara Hew-Butler<\/a>, <em><a href=\"https:\/\/theconversation.com\/institutions\/wayne-state-university-989\">Wayne State University<\/a><\/em><\/p>\n\n\n\n<p>The warmer weather and longer days have inspired reminders to \u201cstay hydrated\u201d and drink eight glasses of water \u2013 or about two liters \u2013 a day.<\/p>\n\n\n\n<p>Not to burst anyone\u2019s water bottle, but healthy people can actually <a href=\"https:\/\/www.nbcnews.com\/id\/wbna16614865\">die<\/a> from drinking too much water. I am an <a href=\"https:\/\/education.wayne.edu\/profile\/gr7894\">exercise physiologist<\/a>, and my research focuses on <a href=\"https:\/\/doi.org\/10.3390\/nu11071539\">overhydration<\/a> and how drinking too much water affects the body. Since water \u2013 and sodium \u2013 balance is essential to life, it is <a href=\"https:\/\/doi.org\/%2010.1097\/JSM.0000000000000221\">extremely rare<\/a> for people to die from drinking too much \u2013 or too little \u2013 fluid. In most cases, your body\u2019s finely tuned molecular processes are unconsciously taking care of you.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img src=\"https:\/\/images.theconversation.com\/files\/395811\/original\/file-20210419-19-vcyb4q.jpg?ixlib=rb-1.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip\" alt=\"A young football player drinking water.\"\/><figcaption>A high school football player drinks water during practice. Many coaches have stressed hydration in recent years. <a href=\"https:\/\/www.gettyimages.com\/detail\/photo\/american-football-players-including-teenagers-in-royalty-free-image\/sb10064896w-001?adppopup=true\">Darrin Klimek\/Getty Images<\/a><\/figcaption><\/figure>\n\n\n\n<h2>Water out, water in<\/h2>\n\n\n\n<p>As spring unfolds, hydration challenges take root across <a href=\"https:\/\/wmich.edu\/rec\/hydrationchallenge\">schools<\/a>, <a href=\"https:\/\/michigansportsalliance.org\/hydrationchallenge\">sports<\/a> and <a href=\"https:\/\/documents.ascension.org\/communications\/benefits2017\/SmartHealth_Hydration_Challenge.pdf\">workplaces<\/a>. These heavily marketed hydration challenges serve to cultivate both camaraderie and friendly competition to ensure that we drink compulsory amounts of water throughout the day.<\/p>\n\n\n\n<p>Hydration and \u201c<a href=\"https:\/\/www.fwweekly.com\/2016\/07\/13\/the-gym-and-i-water-gallon-challenge\/\">Gallon Challenges<\/a>\u201d support the widely held belief that water consumption beyond physiological need \u2013 or thirst \u2013 is healthy.<\/p>\n\n\n\n<p>But this is not so. Individual body water needs \u2013 intake \u2013 are primarily based upon how much water people lose. How much much water each person needs to drink mainly depends on <a href=\"https:\/\/www.researchgate.net\/publication\/6928174_Updated_Fluid_Recommendation_Position_Statement_From_the_International_Marathon_Medical_Directors_Association_IMMDA\">three factors:<\/a><\/p>\n\n\n\n<ul><li>Body weight. Bigger people need more water.<\/li><li>Environmental temperature. When it\u2019s hotter, people sweat and lose water.<\/li><li>Physical activity levels. Increased exercise intensity increases sweat water losses.<\/li><\/ul>\n\n\n\n<p>Therefore, a \u201cone size fits all\u201d fluid replacement strategy, such as drinking eight glasses of eight ounces of water per day, is inappropriate for everyone.<\/p>\n\n\n\n<p>It remains <a href=\"https:\/\/doi.org\/10.1152\/ajpregu.00365.2002\">unclear where the \u201c8 x 8\u201d water intake recommendation<\/a> comes from. Perhaps, this two-liter intake threshold is derived from a misinterpretation of original recommendations offered by the <a href=\"https:\/\/doi.org\/10.1001\/jama.2018.4930\">U.S. Food and Nutrition Board in 1945<\/a> as well as the <a href=\"https:\/\/doi.org\/10.2903\/sp.efsa.2019.EN-1679\">2017 European Food Safety Authority,<\/a> which states the daily recommended amount of water includes all beverages plus the moisture contained in foods.<\/p>\n\n\n\n<p>This means that the moisture contained in foods, especially fresh fruits, sodas, juices, soups, milk, coffee and, yes, even beer, contributes to this daily recommended water requirement. These guidelines go on to suggest that most of the recommended water content can be accomplished without drinking additional cups of plain water.<\/p>\n\n\n\n<p>And, it is important to note that while <a href=\"https:\/\/doi.org\/10.1152\/ajpregu.1982.242.5.R522\">alcohol has diuretic properties<\/a> \u2013 ethanol acts directly on the kidneys to make us pee more \u2013 <a href=\"https:\/\/doi.org\/%2010.1097\/jes.0b013e3180a02cc1\">caffeinated beverages, like tea and coffee, do not increase urinary water losses<\/a> above the amount of water contained in these beverages.<\/p>\n\n\n\n<h2>King kidney<\/h2>\n\n\n\n<p>Now, you may be wondering why this is so. After all, you\u2019ve heard from a lot of people that you need to drink more, more, more.<\/p>\n\n\n\n<p>Because total body water balance, or what we exercise scientists call homeostasis, is complicated, mammals survive by making <a href=\"https:\/\/doi.org\/10.1056\/NEJMra1404726\">real-time adjustments at the kidney<\/a>. That\u2019s why when it comes to hydration, our kidneys are king.<\/p>\n\n\n\n<p>Within each kidney \u2013 we need only one (i.e., we are born with a spare, just in case) \u2013 is an <a href=\"https:\/\/doi.org\/10.1056\/NEJMra1404726\">undercover network of aquaporin-2 (AQP-2) water channels<\/a> which respond to a <a href=\"https:\/\/doi.org\/10.1016\/S1521-690X(03)00049-6\">hormone<\/a> called arginine vasopressin. This is the body\u2019s main anti-diuretic (water retention) hormone. It is secreted by the posterior pituitary gland in response to nerve signals sent from specialized <a href=\"https:\/\/doi.org\/10.1038\/nrn2400\">brain sensors<\/a> which detect subtle changes in water balance. These specialized sensors are called circumventricular organs.<\/p>\n\n\n\n<p>The kidneys will make molecular adjustments to both underhydration and overhydration within <a href=\"https:\/\/doi.org\/10.1152\/ajprenal.1992.262.6.F989\">40 seconds<\/a> in response to any upset in the water balance. These adjustments result from the mobilization armies of AQP-2 water channels, numbering about <a href=\"https:\/\/doi.org\/10.1152\/ajprenal.1997.272.1.F3\">12 million per collecting duct cell<\/a>.<\/p>\n\n\n\n<p>This is why when we drink more water than our body needs \u2013 above thirst \u2013 we immediately have to pee out any excess water. Or when we forget our water bottle during practice, we stop peeing to conserve body water. This quick coordinated action between the <a href=\"https:\/\/doi.org\/10.3390\/nu11071539\">brain, cranial nerves and kidneys<\/a> is far more efficient and precise than any phone app, gadget or personalized recommendation available. https:\/\/www.youtube.com\/embed\/UXUvOIoTUWI?wmode=transparent&amp;start=0 \u2018Good Morning America\u2019 hosts took a water challenge. These contests perpetuate the idea that it\u2019s good to drink eight glasses of water a day.<\/p>\n\n\n\n<h2>Is there anything good to come out of this?<\/h2>\n\n\n\n<p>Data suggests that drinking about two liters of water per day <a href=\"https:\/\/doi.org\/10.1152\/ajpregu.00365.2002\">reduces kidney stone formation<\/a> in people with a history of kidney stones and decreases the number of <a href=\"https:\/\/doi.org\/10.1001\/jamainternmed.2018.4204\">bladder infections<\/a> in people with a history of bladder infections.<\/p>\n\n\n\n<p>Improvement in <a href=\"https:\/\/doi.org\/10.3390\/nu11010070\">skin complexion, kidney function<\/a> and <a href=\"https:\/\/doi.org\/10.1016\/j.jped.2017.01.005\">constipation<\/a>, with increased water consumption, are not clearly supported by science. Drinking extra water alone <a href=\"https:\/\/doi.org\/10.1001\/jamapediatrics.2017.0012\">does not help kids lose weight<\/a> unless water intake replaces the ingestion of higher-caloric beverages, such as soda, or makes people feel \u201c<a href=\"https:\/\/doi.org\/10.1002\/oby.21167\">full<\/a>\u201d before meals.<\/p>\n\n\n\n<p>Drinking water can affect some people\u2019s mental state. Some studies report <a href=\"https:\/\/doi.org\/10.1017\/S0007114513004455\">better cognitive performance<\/a> after increasing water intake; while females with anxiety report <a href=\"https:\/\/journals.lww.com\/jonmd\/Abstract\/1974\/01000\/COMPULSIVE_WATER_DRINKING__A_Review_of_the.10.aspx\">compulsive water intake makes them feel better<\/a>, likely from activation of <a href=\"https:\/\/doi.org\/10.1016\/j.cell.2007.09.018\">reward circuits<\/a> that increase dopamine. Many <a href=\"https:\/\/doi.org\/10.1016\/j.schres.2014.06.001\">schizophrenic patients are compulsive water drinkers<\/a>, stating that \u201c<a href=\"https:\/\/doi.org\/10.1001\/archpsyc.1960.03590070102012\">voices\u201d tell them to drink<\/a> and that drinking water suppresses these voices.<\/p>\n\n\n\n<p>[<em>Get facts about coronavirus and the latest research.<\/em> <a href=\"https:\/\/theconversation.com\/us\/newsletters\/the-daily-3?utm_source=TCUS&amp;utm_medium=inline-link&amp;utm_campaign=newsletter-text&amp;utm_content=coronavirus-facts\">Sign up for The Conversation\u2019s newsletter.<\/a>]<\/p>\n\n\n\n<p>Of note, brain imaging studies confirm that superfluous drinking is <a href=\"https:\/\/doi.org\/10.1073\/pnas.1403382111\">unpleasant<\/a> and requires <a href=\"https:\/\/doi.org\/10.1073\/pnas.1613929113\">greater muscular effort<\/a> than drinking when thirsty. Our brain tries to discourage chronic overdrinking, or polydipsia, because \u201c<a href=\"https:\/\/doi.org\/10.1186\/1752-1947-6-376\">social polydipsia<\/a>\u201d causes chronic peeing (polyuria), which can lead to internal plumbing modifications such as <a href=\"https:\/\/doi.org\/10.1176\/ajp.140.7.915\">bladder distention, ureter dilation, hydronephrosis and renal failure<\/a>.<\/p>\n\n\n\n<p>So, do you need to drink eight glasses of water per day? Unless you are thirsty, drinking extra water will probably not offer superior health benefits but probably is not harmful either. However, if kidneys could talk, they would say that hydration challenges represent nothing more than highly marketed peeing contests.<\/p>\n\n\n\n<p><a href=\"https:\/\/theconversation.com\/profiles\/tamara-hew-butler-519686\">Tamara Hew-Butler<\/a>, Associate Professor of Exercise and Sports Science, <em><a href=\"https:\/\/theconversation.com\/institutions\/wayne-state-university-989\">Wayne State University<\/a><\/em><\/p>\n\n\n\n<p>This article is republished from <a href=\"https:\/\/theconversation.com\">The Conversation<\/a> under a Creative Commons license. Read the <a href=\"https:\/\/theconversation.com\/do-you-really-need-8-glasses-of-water-a-day-an-exercise-scientist-explains-why-your-kidneys-say-no-159020\">original article<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Tamara Hew-Butler, Wayne State University The warmer weather and longer days have inspired reminders to \u201cstay hydrated\u201d and drink eight glasses of water \u2013 or about two liters \u2013 a day. Not to burst anyone\u2019s water bottle, but healthy people can actually die from drinking too much water. I am an exercise physiologist, and my [&hellip;]<\/p>\n","protected":false},"author":44,"featured_media":25158,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[42],"tags":[9800,9214],"_links":{"self":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts\/25157"}],"collection":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/users\/44"}],"replies":[{"embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/comments?post=25157"}],"version-history":[{"count":2,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts\/25157\/revisions"}],"predecessor-version":[{"id":25164,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts\/25157\/revisions\/25164"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/media\/25158"}],"wp:attachment":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/media?parent=25157"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/categories?post=25157"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/tags?post=25157"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}