Water Debate
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The Mythical Daily Water Requirement (60-second Science)
There's no evidence that humans actually need the oft-cited "eight-glasses-per-day" of water. Karen Hopkin reports.
Somewhere along the line you’ve probably heard that you should drink eight glasses of water a day. It’s supposed to make your skin supple, keep your organs flush and help you avoid overeating. Now doctors from the University of Pennsylvania say that’s hogwash. After exploring the health effects of hydration, they conclude that the purported benefits of drinking lots of water are not backed by any solid evidence—or liquid evidence, either. The physicians present their findings in the June issue of the Journal of the American Society of Nephrology.
Okay, humans can’t last more than a few days without water. But very little research has been done to assess just how much water a healthy individual needs. So the Pennsylvania docs scanned the literature. They discovered that drinking water does help the kidneys clear out salt and such. But those studies don’t suggest any sort of clinical benefit. There are no studies that show that chugging H2O will curb your appetite. Ditto for drinking water to enhance your skin tone. In fact, no studies indicate that people should drink eight glasses of water a day. Where that number came from no one seems to know. But in the end, it turns out to be all wet.
—Karen Hopkin
NPR:
Five Myths About Drinking Water
by Allison Aubrey
Aug. 10, 2006
Morning Edition, April 3, 2008 · Is bottled water better for you than tap? Or should you choose vitamin-enriched water over sparkling? Experts say, skip it all. None of these products are likely to make you any healthier. Below, we look at five major myths about the benefits of drinking water.
But first, how do you know if you're drinking enough water? Experts say there's an easy way to judge. If you're not thirsty, you're fluid intake is likely "just right."
Myth No. 1: Drink Eight Glasses Each Day
Scientists say there's no clear health benefit to chugging or even sipping water all day. So where does the standard advice of drinking eight glasses each day come from? "Nobody really knows," says Dr. Stanley Goldfarb, a kidney expert at the University of Pennsylvania.
Myth No. 2: Drinking Lots of Water Helps Clear Out Toxins
The kidneys filter toxins from our bloodstreams. Then the toxins clear through the urine. The question is, does drinking extra water each day improve the function of the kidneys?
"No," says Goldfarb. "In fact, drinking large amounts of water surprisingly tends to reduce the kidney's ability to function as a filter. It's a subtle decline, but definite."
Myth No. 3: Lots of Water Equals Healthier Skin
The body is already 60 percent water. So, if you take a 200-pound man, he's 120 pounds of water.
Adding a few extra glasses of water each day has limited effect. "It's such a tiny part of what's in the body," says Goldfarb. "It's very unlikely that one's getting any benefit." His full editorial is published in the current issue of the Journal of the American Society of Nephrology.
One study published in 2007 on the cosmetic benefit of drinking water suggests that 500 ml of water increases capillary blood flow in the skin. "But it's unclear whether these changes are clinically significant," says Goldfarb.
Myth No. 4: Drinking Extra Water Leads to Weight Loss
A more accurate statement may be: Drinking water is a helpful tool for dieters.
"Water is a great strategy for dieters because it has no calories," says Madeline Fernstrom of the University of Pittsburgh. "So you can keep your mouth busy without food and get the sense of satisfaction."
But water is not magical, she adds. Other zero-calorie options such as diet sodas are fine, too.
Myth No. 5: It's Easy to Get Dehydrated During a Workout
Dehydration sets in when a person has lost 2 percent of his or her body weight. So for a 200-pound man, this means losing 4 pounds of water.
Marathon runners, bikers and hikers all need to recognize the signs of dehydration. "It is also obvious that individuals in hot, dry climates have increased need for water," says Goldfarb.
The American College of Sports Medicine recommends that athletes drink 16 ounces of fluids a couple of hours before starting sports practice.
But for a stroll in the park, no water bottle is necessary. Goldfarb's advice: Just drink when you're thirsty.
And Finally:
12 August 2002
Recommended Water Intake A Myth
by Kate Melville
It has become accepted wisdom: "Drink at least eight glasses of water a day!" Not necessarily, says a DMS physician Heinz Valtin, MD. The universal advice that has made guzzling water a national pastime is more urban myth than medical dogma and appears to lack scientific proof, he found. In an invited review published online by the American Journal of Physiology August 8, Valtin, professor emeritus of physiology at Dartmouth Medical School, reports no supporting evidence to back this popular counsel, commonly known as "8 x 8" (for eight, eight-ounce glasses). The review will also appear in a later issue of the journal.
Valtin, a kidney specialist and author of two widely used textbooks on the kidney and water balance, sought to find the origin of this dictum and to examine the scientific evidence, if any, that might support it. He observes that we see the exhortation everywhere: from health writers, nutritionists, even physicians. Valtin doubts its validity. Indeed, he finds it, "difficult to believe that evolution left us with a chronic water deficit that needs to be compensated by forcing a high fluid intake."
The 8 x 8 rule is slavishly followed. Everywhere, people carry bottles of water, constantly sipping from them; it is acceptable to drink water anywhere, anytime. A pamphlet distributed at one southern California university even counsels its students to "carry a water bottle with you. Drink often while sitting in class..."
How did the obsession start? Is there any scientific evidence that supports the recommendation? Does the habit promote good health? Might it be harmful?
Valtin thinks the notion may have started when the Food and Nutrition Board of the National Research Council recommended approximately "1 milliliter of water for each calorie of food," which would amount to roughly two to two-and-a-half quarts per day (64 to 80 ounces). Although in its next sentence, the Board stated "most of this quantity is contained in prepared foods," that last sentence may have been missed, so that the recommendation was erroneously interpreted as how much water one should drink each day.
He found no scientific studies in support of 8 x 8. Rather, surveys of fluid intake on healthy adults of both genders, published as peer-reviewed documents, strongly suggest that such large amounts are not needed. His conclusion is supported by published studies showing that caffeinated drinks, such as most coffee, tea and soft drinks, may indeed be counted toward the daily total. He also points to the quantity of published experiments that attest to the capability of the human body for maintaining proper water balance.
Valtin emphasizes that his conclusion is limited to healthy adults in a temperate climate leading a largely sedentary existence -- precisely, he points out, the population and conditions that the "at least" in 8 x 8 refers to. At the same time, he stresses that large intakes of fluid, equal to and greater than 8 x 8, are advisable for the treatment or prevention of some diseases, such as kidney stones, as well as under special circumstances, such as strenuous physical activity, long airplane flights or hot weather. But barring those exceptions, he concludes that we are currently drinking enough and possibly even more than enough.
Despite the dearth of compelling evidence, then, What's the harm? "The fact is that, potentially, there is harm even in water," explains Valtin. Even modest increases in fluid intake can result in "water intoxication" if one's kidneys are unable to excrete enough water (urine). Such instances are not unheard of, and they have led to mental confusion and even death in athletes, in teenagers after ingesting the recreational drug Ecstasy, and in ordinary patients.
And he lists other disadvantages of a high water intake: (a) possible exposure to pollutants, especially if sustained over many years; (b) frequent urination, which can be both inconvenient and embarrassing; (c) expense, for those who satisfy the 8 x 8 requirements with bottled water; and (d) feelings of guilt for not achieving 8 x 8.
Other claims discredited by scientific evidence that Valtin discusses include:
Thirst Is Too Late. It is often stated that by the time people are thirsty, they are already dehydrated. On the contrary, thirst begins when the concentration of blood (an accurate indicator of our state of hydration) has risen by less than two percent, whereas most experts would define dehydration as beginning when that concentration has risen by at least five percent.
Dark Urine Means Dehydration. At normal urinary volume and color, the concentration of the blood is within the normal range and nowhere near the values that are seen in meaningful dehydration. Therefore, the warning that dark urine reflects dehydration is alarmist and false in most instances.
Is there scientific documentation that we do not need to drink "8 x 8"? There is highly suggestive evidence, says Valtin. First is the voluminous scientific literature on the efficacy of the osmoregulatory system that maintains water balance through the antidiuretic hormone and thirst. Second, published surveys document that the mean daily fluid intake of thousands of presumably healthy humans is less than the roughly two quarts prescribed by 8 x 8. Valtin argues that, in view of this evidence, the burden of proof that everyone needs 8 x 8 should fall on those who persist in advocating the high fluid intake without, apparently, citing any scientific support.
Finally, strong evidence now indicates that not all of the prescribed fluid need be in the form of water. Careful peer-reviewed experiments have shown that caffeinated drinks should indeed count toward the daily fluid intake in the vast majority of persons. To a lesser extent, the same probably can be said for dilute alcoholic beverages, such as beer, if taken in moderation.
"Thus, I have found no scientific proof that absolutely every person must 'drink at least eight glasses of water a day'," says Valtin. While there is some evidence that the risk of certain diseases can be lowered by high water intake, the quantities needed for this beneficial effect may be less than 8 x 8, and the recommendation can be limited to those particularly susceptible to the diseases in question.
There's no evidence that humans actually need the oft-cited "eight-glasses-per-day" of water. Karen Hopkin reports.
Somewhere along the line you’ve probably heard that you should drink eight glasses of water a day. It’s supposed to make your skin supple, keep your organs flush and help you avoid overeating. Now doctors from the University of Pennsylvania say that’s hogwash. After exploring the health effects of hydration, they conclude that the purported benefits of drinking lots of water are not backed by any solid evidence—or liquid evidence, either. The physicians present their findings in the June issue of the Journal of the American Society of Nephrology.
Okay, humans can’t last more than a few days without water. But very little research has been done to assess just how much water a healthy individual needs. So the Pennsylvania docs scanned the literature. They discovered that drinking water does help the kidneys clear out salt and such. But those studies don’t suggest any sort of clinical benefit. There are no studies that show that chugging H2O will curb your appetite. Ditto for drinking water to enhance your skin tone. In fact, no studies indicate that people should drink eight glasses of water a day. Where that number came from no one seems to know. But in the end, it turns out to be all wet.
—Karen Hopkin
NPR:
Five Myths About Drinking Water
by Allison Aubrey
Aug. 10, 2006
Morning Edition, April 3, 2008 · Is bottled water better for you than tap? Or should you choose vitamin-enriched water over sparkling? Experts say, skip it all. None of these products are likely to make you any healthier. Below, we look at five major myths about the benefits of drinking water.
But first, how do you know if you're drinking enough water? Experts say there's an easy way to judge. If you're not thirsty, you're fluid intake is likely "just right."
Myth No. 1: Drink Eight Glasses Each Day
Scientists say there's no clear health benefit to chugging or even sipping water all day. So where does the standard advice of drinking eight glasses each day come from? "Nobody really knows," says Dr. Stanley Goldfarb, a kidney expert at the University of Pennsylvania.
Myth No. 2: Drinking Lots of Water Helps Clear Out Toxins
The kidneys filter toxins from our bloodstreams. Then the toxins clear through the urine. The question is, does drinking extra water each day improve the function of the kidneys?
"No," says Goldfarb. "In fact, drinking large amounts of water surprisingly tends to reduce the kidney's ability to function as a filter. It's a subtle decline, but definite."
Myth No. 3: Lots of Water Equals Healthier Skin
The body is already 60 percent water. So, if you take a 200-pound man, he's 120 pounds of water.
Adding a few extra glasses of water each day has limited effect. "It's such a tiny part of what's in the body," says Goldfarb. "It's very unlikely that one's getting any benefit." His full editorial is published in the current issue of the Journal of the American Society of Nephrology.
One study published in 2007 on the cosmetic benefit of drinking water suggests that 500 ml of water increases capillary blood flow in the skin. "But it's unclear whether these changes are clinically significant," says Goldfarb.
Myth No. 4: Drinking Extra Water Leads to Weight Loss
A more accurate statement may be: Drinking water is a helpful tool for dieters.
"Water is a great strategy for dieters because it has no calories," says Madeline Fernstrom of the University of Pittsburgh. "So you can keep your mouth busy without food and get the sense of satisfaction."
But water is not magical, she adds. Other zero-calorie options such as diet sodas are fine, too.
Myth No. 5: It's Easy to Get Dehydrated During a Workout
Dehydration sets in when a person has lost 2 percent of his or her body weight. So for a 200-pound man, this means losing 4 pounds of water.
Marathon runners, bikers and hikers all need to recognize the signs of dehydration. "It is also obvious that individuals in hot, dry climates have increased need for water," says Goldfarb.
The American College of Sports Medicine recommends that athletes drink 16 ounces of fluids a couple of hours before starting sports practice.
But for a stroll in the park, no water bottle is necessary. Goldfarb's advice: Just drink when you're thirsty.
And Finally:
12 August 2002
Recommended Water Intake A Myth
by Kate Melville
It has become accepted wisdom: "Drink at least eight glasses of water a day!" Not necessarily, says a DMS physician Heinz Valtin, MD. The universal advice that has made guzzling water a national pastime is more urban myth than medical dogma and appears to lack scientific proof, he found. In an invited review published online by the American Journal of Physiology August 8, Valtin, professor emeritus of physiology at Dartmouth Medical School, reports no supporting evidence to back this popular counsel, commonly known as "8 x 8" (for eight, eight-ounce glasses). The review will also appear in a later issue of the journal.
Valtin, a kidney specialist and author of two widely used textbooks on the kidney and water balance, sought to find the origin of this dictum and to examine the scientific evidence, if any, that might support it. He observes that we see the exhortation everywhere: from health writers, nutritionists, even physicians. Valtin doubts its validity. Indeed, he finds it, "difficult to believe that evolution left us with a chronic water deficit that needs to be compensated by forcing a high fluid intake."
The 8 x 8 rule is slavishly followed. Everywhere, people carry bottles of water, constantly sipping from them; it is acceptable to drink water anywhere, anytime. A pamphlet distributed at one southern California university even counsels its students to "carry a water bottle with you. Drink often while sitting in class..."
How did the obsession start? Is there any scientific evidence that supports the recommendation? Does the habit promote good health? Might it be harmful?
Valtin thinks the notion may have started when the Food and Nutrition Board of the National Research Council recommended approximately "1 milliliter of water for each calorie of food," which would amount to roughly two to two-and-a-half quarts per day (64 to 80 ounces). Although in its next sentence, the Board stated "most of this quantity is contained in prepared foods," that last sentence may have been missed, so that the recommendation was erroneously interpreted as how much water one should drink each day.
He found no scientific studies in support of 8 x 8. Rather, surveys of fluid intake on healthy adults of both genders, published as peer-reviewed documents, strongly suggest that such large amounts are not needed. His conclusion is supported by published studies showing that caffeinated drinks, such as most coffee, tea and soft drinks, may indeed be counted toward the daily total. He also points to the quantity of published experiments that attest to the capability of the human body for maintaining proper water balance.
Valtin emphasizes that his conclusion is limited to healthy adults in a temperate climate leading a largely sedentary existence -- precisely, he points out, the population and conditions that the "at least" in 8 x 8 refers to. At the same time, he stresses that large intakes of fluid, equal to and greater than 8 x 8, are advisable for the treatment or prevention of some diseases, such as kidney stones, as well as under special circumstances, such as strenuous physical activity, long airplane flights or hot weather. But barring those exceptions, he concludes that we are currently drinking enough and possibly even more than enough.
Despite the dearth of compelling evidence, then, What's the harm? "The fact is that, potentially, there is harm even in water," explains Valtin. Even modest increases in fluid intake can result in "water intoxication" if one's kidneys are unable to excrete enough water (urine). Such instances are not unheard of, and they have led to mental confusion and even death in athletes, in teenagers after ingesting the recreational drug Ecstasy, and in ordinary patients.
And he lists other disadvantages of a high water intake: (a) possible exposure to pollutants, especially if sustained over many years; (b) frequent urination, which can be both inconvenient and embarrassing; (c) expense, for those who satisfy the 8 x 8 requirements with bottled water; and (d) feelings of guilt for not achieving 8 x 8.
Other claims discredited by scientific evidence that Valtin discusses include:
Thirst Is Too Late. It is often stated that by the time people are thirsty, they are already dehydrated. On the contrary, thirst begins when the concentration of blood (an accurate indicator of our state of hydration) has risen by less than two percent, whereas most experts would define dehydration as beginning when that concentration has risen by at least five percent.
Dark Urine Means Dehydration. At normal urinary volume and color, the concentration of the blood is within the normal range and nowhere near the values that are seen in meaningful dehydration. Therefore, the warning that dark urine reflects dehydration is alarmist and false in most instances.
Is there scientific documentation that we do not need to drink "8 x 8"? There is highly suggestive evidence, says Valtin. First is the voluminous scientific literature on the efficacy of the osmoregulatory system that maintains water balance through the antidiuretic hormone and thirst. Second, published surveys document that the mean daily fluid intake of thousands of presumably healthy humans is less than the roughly two quarts prescribed by 8 x 8. Valtin argues that, in view of this evidence, the burden of proof that everyone needs 8 x 8 should fall on those who persist in advocating the high fluid intake without, apparently, citing any scientific support.
Finally, strong evidence now indicates that not all of the prescribed fluid need be in the form of water. Careful peer-reviewed experiments have shown that caffeinated drinks should indeed count toward the daily fluid intake in the vast majority of persons. To a lesser extent, the same probably can be said for dilute alcoholic beverages, such as beer, if taken in moderation.
"Thus, I have found no scientific proof that absolutely every person must 'drink at least eight glasses of water a day'," says Valtin. While there is some evidence that the risk of certain diseases can be lowered by high water intake, the quantities needed for this beneficial effect may be less than 8 x 8, and the recommendation can be limited to those particularly susceptible to the diseases in question.
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Replies
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The Mythical Daily Water Requirement (60-second Science)
There's no evidence that humans actually need the oft-cited "eight-glasses-per-day" of water. Karen Hopkin reports.
Somewhere along the line you’ve probably heard that you should drink eight glasses of water a day. It’s supposed to make your skin supple, keep your organs flush and help you avoid overeating. Now doctors from the University of Pennsylvania say that’s hogwash. After exploring the health effects of hydration, they conclude that the purported benefits of drinking lots of water are not backed by any solid evidence—or liquid evidence, either. The physicians present their findings in the June issue of the Journal of the American Society of Nephrology.
Okay, humans can’t last more than a few days without water. But very little research has been done to assess just how much water a healthy individual needs. So the Pennsylvania docs scanned the literature. They discovered that drinking water does help the kidneys clear out salt and such. But those studies don’t suggest any sort of clinical benefit. There are no studies that show that chugging H2O will curb your appetite. Ditto for drinking water to enhance your skin tone. In fact, no studies indicate that people should drink eight glasses of water a day. Where that number came from no one seems to know. But in the end, it turns out to be all wet.
—Karen Hopkin
NPR:
Five Myths About Drinking Water
by Allison Aubrey
Aug. 10, 2006
Morning Edition, April 3, 2008 · Is bottled water better for you than tap? Or should you choose vitamin-enriched water over sparkling? Experts say, skip it all. None of these products are likely to make you any healthier. Below, we look at five major myths about the benefits of drinking water.
But first, how do you know if you're drinking enough water? Experts say there's an easy way to judge. If you're not thirsty, you're fluid intake is likely "just right."
Myth No. 1: Drink Eight Glasses Each Day
Scientists say there's no clear health benefit to chugging or even sipping water all day. So where does the standard advice of drinking eight glasses each day come from? "Nobody really knows," says Dr. Stanley Goldfarb, a kidney expert at the University of Pennsylvania.
Myth No. 2: Drinking Lots of Water Helps Clear Out Toxins
The kidneys filter toxins from our bloodstreams. Then the toxins clear through the urine. The question is, does drinking extra water each day improve the function of the kidneys?
"No," says Goldfarb. "In fact, drinking large amounts of water surprisingly tends to reduce the kidney's ability to function as a filter. It's a subtle decline, but definite."
Myth No. 3: Lots of Water Equals Healthier Skin
The body is already 60 percent water. So, if you take a 200-pound man, he's 120 pounds of water.
Adding a few extra glasses of water each day has limited effect. "It's such a tiny part of what's in the body," says Goldfarb. "It's very unlikely that one's getting any benefit." His full editorial is published in the current issue of the Journal of the American Society of Nephrology.
One study published in 2007 on the cosmetic benefit of drinking water suggests that 500 ml of water increases capillary blood flow in the skin. "But it's unclear whether these changes are clinically significant," says Goldfarb.
Myth No. 4: Drinking Extra Water Leads to Weight Loss
A more accurate statement may be: Drinking water is a helpful tool for dieters.
"Water is a great strategy for dieters because it has no calories," says Madeline Fernstrom of the University of Pittsburgh. "So you can keep your mouth busy without food and get the sense of satisfaction."
But water is not magical, she adds. Other zero-calorie options such as diet sodas are fine, too.
Myth No. 5: It's Easy to Get Dehydrated During a Workout
Dehydration sets in when a person has lost 2 percent of his or her body weight. So for a 200-pound man, this means losing 4 pounds of water.
Marathon runners, bikers and hikers all need to recognize the signs of dehydration. "It is also obvious that individuals in hot, dry climates have increased need for water," says Goldfarb.
The American College of Sports Medicine recommends that athletes drink 16 ounces of fluids a couple of hours before starting sports practice.
But for a stroll in the park, no water bottle is necessary. Goldfarb's advice: Just drink when you're thirsty.
And Finally:
12 August 2002
Recommended Water Intake A Myth
by Kate Melville
It has become accepted wisdom: "Drink at least eight glasses of water a day!" Not necessarily, says a DMS physician Heinz Valtin, MD. The universal advice that has made guzzling water a national pastime is more urban myth than medical dogma and appears to lack scientific proof, he found. In an invited review published online by the American Journal of Physiology August 8, Valtin, professor emeritus of physiology at Dartmouth Medical School, reports no supporting evidence to back this popular counsel, commonly known as "8 x 8" (for eight, eight-ounce glasses). The review will also appear in a later issue of the journal.
Valtin, a kidney specialist and author of two widely used textbooks on the kidney and water balance, sought to find the origin of this dictum and to examine the scientific evidence, if any, that might support it. He observes that we see the exhortation everywhere: from health writers, nutritionists, even physicians. Valtin doubts its validity. Indeed, he finds it, "difficult to believe that evolution left us with a chronic water deficit that needs to be compensated by forcing a high fluid intake."
The 8 x 8 rule is slavishly followed. Everywhere, people carry bottles of water, constantly sipping from them; it is acceptable to drink water anywhere, anytime. A pamphlet distributed at one southern California university even counsels its students to "carry a water bottle with you. Drink often while sitting in class..."
How did the obsession start? Is there any scientific evidence that supports the recommendation? Does the habit promote good health? Might it be harmful?
Valtin thinks the notion may have started when the Food and Nutrition Board of the National Research Council recommended approximately "1 milliliter of water for each calorie of food," which would amount to roughly two to two-and-a-half quarts per day (64 to 80 ounces). Although in its next sentence, the Board stated "most of this quantity is contained in prepared foods," that last sentence may have been missed, so that the recommendation was erroneously interpreted as how much water one should drink each day.
He found no scientific studies in support of 8 x 8. Rather, surveys of fluid intake on healthy adults of both genders, published as peer-reviewed documents, strongly suggest that such large amounts are not needed. His conclusion is supported by published studies showing that caffeinated drinks, such as most coffee, tea and soft drinks, may indeed be counted toward the daily total. He also points to the quantity of published experiments that attest to the capability of the human body for maintaining proper water balance.
Valtin emphasizes that his conclusion is limited to healthy adults in a temperate climate leading a largely sedentary existence -- precisely, he points out, the population and conditions that the "at least" in 8 x 8 refers to. At the same time, he stresses that large intakes of fluid, equal to and greater than 8 x 8, are advisable for the treatment or prevention of some diseases, such as kidney stones, as well as under special circumstances, such as strenuous physical activity, long airplane flights or hot weather. But barring those exceptions, he concludes that we are currently drinking enough and possibly even more than enough.
Despite the dearth of compelling evidence, then, What's the harm? "The fact is that, potentially, there is harm even in water," explains Valtin. Even modest increases in fluid intake can result in "water intoxication" if one's kidneys are unable to excrete enough water (urine). Such instances are not unheard of, and they have led to mental confusion and even death in athletes, in teenagers after ingesting the recreational drug Ecstasy, and in ordinary patients.
And he lists other disadvantages of a high water intake: (a) possible exposure to pollutants, especially if sustained over many years; (b) frequent urination, which can be both inconvenient and embarrassing; (c) expense, for those who satisfy the 8 x 8 requirements with bottled water; and (d) feelings of guilt for not achieving 8 x 8.
Other claims discredited by scientific evidence that Valtin discusses include:
Thirst Is Too Late. It is often stated that by the time people are thirsty, they are already dehydrated. On the contrary, thirst begins when the concentration of blood (an accurate indicator of our state of hydration) has risen by less than two percent, whereas most experts would define dehydration as beginning when that concentration has risen by at least five percent.
Dark Urine Means Dehydration. At normal urinary volume and color, the concentration of the blood is within the normal range and nowhere near the values that are seen in meaningful dehydration. Therefore, the warning that dark urine reflects dehydration is alarmist and false in most instances.
Is there scientific documentation that we do not need to drink "8 x 8"? There is highly suggestive evidence, says Valtin. First is the voluminous scientific literature on the efficacy of the osmoregulatory system that maintains water balance through the antidiuretic hormone and thirst. Second, published surveys document that the mean daily fluid intake of thousands of presumably healthy humans is less than the roughly two quarts prescribed by 8 x 8. Valtin argues that, in view of this evidence, the burden of proof that everyone needs 8 x 8 should fall on those who persist in advocating the high fluid intake without, apparently, citing any scientific support.
Finally, strong evidence now indicates that not all of the prescribed fluid need be in the form of water. Careful peer-reviewed experiments have shown that caffeinated drinks should indeed count toward the daily fluid intake in the vast majority of persons. To a lesser extent, the same probably can be said for dilute alcoholic beverages, such as beer, if taken in moderation.
"Thus, I have found no scientific proof that absolutely every person must 'drink at least eight glasses of water a day'," says Valtin. While there is some evidence that the risk of certain diseases can be lowered by high water intake, the quantities needed for this beneficial effect may be less than 8 x 8, and the recommendation can be limited to those particularly susceptible to the diseases in question.0 -
Despite what these two article writers may say... I'll stick with the official guidelines actually set into place by the American College of Sports Medicine. Somehow, I'd think that they are a more valid source
I hope nobody reads these just for an excuse to not drink water and chug diet Coke instead... I mean, seriously, people...0 -
Those are great articles, but I'm going to stick to drinking my water. The days I drink it I feel TONS better, more focused, more energy, and my skin is clearing up! Oh, and I don't get hungry if I'm drinking plenty. I LOOOOVE ME SOME WATER!0
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I'm not saying you shouldn't drink water. Clearly we all need to stay hydrated. But I think it's interesting that there's so much passion around this issue. This is from WebMD:
Benefits of Drinking Water Oversold?
Researchers Say Evidence Is Lacking for Benefits of Drinking 8 Glasses of Water a Day(continued)
Claim No. 1: Drinking Water Helps Excrete Toxins
Drinking lots of water is widely thought to help improve kidney function and boost the clearance of toxins. One way it could do this, Goldfarb says, is by a mechanism called glomerular filtration, a measure of the kidney's ability to filter and remove waste products.
But in one study the researchers looked at, increased water intake by 12 young and healthy people actually decreased their glomerular filtration rate. And in another study, the rate did not change over time during a six-month period in which older men drank more water to try to improve bladder function.
In other research, increased water intake was found to affect the clearance of many substances by the kidneys, including sodium. But the studies don't prove any sort of clinical benefit, Goldfarb says.
"What almost certainly happens is, any toxins the kidney is responsible for excreting simply get diluted when the person is drinking a lot of water," Goldfarb says.
Claim No. 2: Drinking Water Helps Your Organs Work Better
Water is retained in various organs, so the thinking goes, and they work better with more water in them.
But Goldfarb and Negoianu say how much water is retained varies with the speed with which the water is taken in. If it's sipped, it's more likely to stay in the body than when gulped.
Even so, they could find no studies documenting that increased water intake helped the organs.
Claim No. 3: Drinking Water Reduces Food Intake and Helps You Lose Weight
Drinking more water is widely encouraged to help weight loss, the theory being that the more water you drink, the fuller you will feel and the less you will eat. "The [medical] literature on this is quite conflicted," Goldfarb says.
"Drinking before a meal might decrease intake [according to one study], but another study found [it did] not."
Even so, Goldfarb calls this claim one of the most promising for further study.
Claim No. 4: Drinking Water Improves Skin Tone
"From a quantitative sense, this doesn't make sense," Goldfarb says. The water you drink will be distributed throughout the body. "Such a tiny part of it would end up in the skin," he says.
"It turns out one small study showed there might be an increase in blood flow in those who drink [a lot of] water, but no one has ever looked scientifically [to see if it improves skin tone]."
Claim No. 5: Drinking Water Wards Off Headaches
Headache sufferers often blame water deprivation. But Goldfarb could only find one study that looked at this. The study participants who boosted their water intake had fewer headaches than those who did not, but the results were not statistically significant, meaning they could have been chance findings.
Second Opinion: Health Benefits of Drinking Water
The report provides interesting -- and sometimes surprising -- information, says David Baron, MD, a family physician and chief of staff at Santa Monica-UCLA Medical Center & Orthopaedic Hospital, Calif., who reviewed it for WebMD.
The most surprising finding, he says, was the lack of a scientific link found between drinking a lot of water in order to eat less. "I thought [the suggestion that] filling up your stomach with water might help lose weight makes sense," he says.
The report isn't dismissing the need to drink a healthy amount of fluids, he says. It simply showed no scientific basis to the recommendation to drink eight glasses of water daily.
"There is a lot of individual variation" in exactly how much water or fluid people need," he says.
Most of us, he says, are OK "by trusting our instincts" about how much to drink. "If you have a normal heart, normal kidneys, and normal thirst mechanism, it's not likely you will get dehydrated if there is a sufficient supply of fluids available," he says, and drink when thirsty.
Drinking Water: A Placebo Effect?
Might drinking a lot of water make us think we feel better, look better, and function better? Could there be a placebo effect to those eight daily glasses?
"I'm certain there is," Goldfarb says. "The placebo effect is very strong."
And if you're still convinced lots of water does your body good? No problem. "People say they feel stronger and healthier if they drink more water," he says. "That's fine. If they enjoy that benefit, so be it. [But] those who don't feel that way shouldn't feel obligated to drink the eight glasses."0 -
I'm going to go with the concensus on this one. I have ALOT of problems with UTIs, etc if I don't get MORE than 8glasses of water every day. Not to mention I retain alot of water weight when I don't replace the 8 glasses a day.... when I sweat it all out at the gym, etc.. I need lots of water! And I also find that if i'm constantly drinking my water.... i don't "munch" as much I'd say my beverage intake on a daily basis is 95% water. 0
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The Mythical Daily Water Requirement (60-second Science)
There's no evidence that humans actually need the oft-cited "eight-glasses-per-day" of water. Karen Hopkin reports.
Somewhere along the line you’ve probably heard that you should drink eight glasses of water a day. It’s supposed to make your skin supple, keep your organs flush and help you avoid overeating. Now doctors from the University of Pennsylvania say that’s hogwash. After exploring the health effects of hydration, they conclude that the purported benefits of drinking lots of water are not backed by any solid evidence—or liquid evidence, either. The physicians present their findings in the June issue of the Journal of the American Society of Nephrology.
Okay, humans can’t last more than a few days without water. But very little research has been done to assess just how much water a healthy individual needs. So the Pennsylvania docs scanned the literature. They discovered that drinking water does help the kidneys clear out salt and such. But those studies don’t suggest any sort of clinical benefit. There are no studies that show that chugging H2O will curb your appetite. Ditto for drinking water to enhance your skin tone. In fact, no studies indicate that people should drink eight glasses of water a day. Where that number came from no one seems to know. But in the end, it turns out to be all wet.
—Karen Hopkin
NPR:
Five Myths About Drinking Water
by Allison Aubrey
Aug. 10, 2006
Morning Edition, April 3, 2008 · Is bottled water better for you than tap? Or should you choose vitamin-enriched water over sparkling? Experts say, skip it all. None of these products are likely to make you any healthier. Below, we look at five major myths about the benefits of drinking water.
But first, how do you know if you're drinking enough water? Experts say there's an easy way to judge. If you're not thirsty, you're fluid intake is likely "just right."
Myth No. 1: Drink Eight Glasses Each Day
Scientists say there's no clear health benefit to chugging or even sipping water all day. So where does the standard advice of drinking eight glasses each day come from? "Nobody really knows," says Dr. Stanley Goldfarb, a kidney expert at the University of Pennsylvania.
Myth No. 2: Drinking Lots of Water Helps Clear Out Toxins
The kidneys filter toxins from our bloodstreams. Then the toxins clear through the urine. The question is, does drinking extra water each day improve the function of the kidneys?
"No," says Goldfarb. "In fact, drinking large amounts of water surprisingly tends to reduce the kidney's ability to function as a filter. It's a subtle decline, but definite."
Myth No. 3: Lots of Water Equals Healthier Skin
The body is already 60 percent water. So, if you take a 200-pound man, he's 120 pounds of water.
Adding a few extra glasses of water each day has limited effect. "It's such a tiny part of what's in the body," says Goldfarb. "It's very unlikely that one's getting any benefit." His full editorial is published in the current issue of the Journal of the American Society of Nephrology.
One study published in 2007 on the cosmetic benefit of drinking water suggests that 500 ml of water increases capillary blood flow in the skin. "But it's unclear whether these changes are clinically significant," says Goldfarb.
Myth No. 4: Drinking Extra Water Leads to Weight Loss
A more accurate statement may be: Drinking water is a helpful tool for dieters.
"Water is a great strategy for dieters because it has no calories," says Madeline Fernstrom of the University of Pittsburgh. "So you can keep your mouth busy without food and get the sense of satisfaction."
But water is not magical, she adds. Other zero-calorie options such as diet sodas are fine, too.
Myth No. 5: It's Easy to Get Dehydrated During a Workout
Dehydration sets in when a person has lost 2 percent of his or her body weight. So for a 200-pound man, this means losing 4 pounds of water.
Marathon runners, bikers and hikers all need to recognize the signs of dehydration. "It is also obvious that individuals in hot, dry climates have increased need for water," says Goldfarb.
The American College of Sports Medicine recommends that athletes drink 16 ounces of fluids a couple of hours before starting sports practice.
But for a stroll in the park, no water bottle is necessary. Goldfarb's advice: Just drink when you're thirsty.
And Finally:
12 August 2002
Recommended Water Intake A Myth
by Kate Melville
It has become accepted wisdom: "Drink at least eight glasses of water a day!" Not necessarily, says a DMS physician Heinz Valtin, MD. The universal advice that has made guzzling water a national pastime is more urban myth than medical dogma and appears to lack scientific proof, he found. In an invited review published online by the American Journal of Physiology August 8, Valtin, professor emeritus of physiology at Dartmouth Medical School, reports no supporting evidence to back this popular counsel, commonly known as "8 x 8" (for eight, eight-ounce glasses). The review will also appear in a later issue of the journal.
Valtin, a kidney specialist and author of two widely used textbooks on the kidney and water balance, sought to find the origin of this dictum and to examine the scientific evidence, if any, that might support it. He observes that we see the exhortation everywhere: from health writers, nutritionists, even physicians. Valtin doubts its validity. Indeed, he finds it, "difficult to believe that evolution left us with a chronic water deficit that needs to be compensated by forcing a high fluid intake."
The 8 x 8 rule is slavishly followed. Everywhere, people carry bottles of water, constantly sipping from them; it is acceptable to drink water anywhere, anytime. A pamphlet distributed at one southern California university even counsels its students to "carry a water bottle with you. Drink often while sitting in class..."
How did the obsession start? Is there any scientific evidence that supports the recommendation? Does the habit promote good health? Might it be harmful?
Valtin thinks the notion may have started when the Food and Nutrition Board of the National Research Council recommended approximately "1 milliliter of water for each calorie of food," which would amount to roughly two to two-and-a-half quarts per day (64 to 80 ounces). Although in its next sentence, the Board stated "most of this quantity is contained in prepared foods," that last sentence may have been missed, so that the recommendation was erroneously interpreted as how much water one should drink each day.
He found no scientific studies in support of 8 x 8. Rather, surveys of fluid intake on healthy adults of both genders, published as peer-reviewed documents, strongly suggest that such large amounts are not needed. His conclusion is supported by published studies showing that caffeinated drinks, such as most coffee, tea and soft drinks, may indeed be counted toward the daily total. He also points to the quantity of published experiments that attest to the capability of the human body for maintaining proper water balance.
Valtin emphasizes that his conclusion is limited to healthy adults in a temperate climate leading a largely sedentary existence -- precisely, he points out, the population and conditions that the "at least" in 8 x 8 refers to. At the same time, he stresses that large intakes of fluid, equal to and greater than 8 x 8, are advisable for the treatment or prevention of some diseases, such as kidney stones, as well as under special circumstances, such as strenuous physical activity, long airplane flights or hot weather. But barring those exceptions, he concludes that we are currently drinking enough and possibly even more than enough.
Despite the dearth of compelling evidence, then, What's the harm? "The fact is that, potentially, there is harm even in water," explains Valtin. Even modest increases in fluid intake can result in "water intoxication" if one's kidneys are unable to excrete enough water (urine). Such instances are not unheard of, and they have led to mental confusion and even death in athletes, in teenagers after ingesting the recreational drug Ecstasy, and in ordinary patients.
And he lists other disadvantages of a high water intake: (a) possible exposure to pollutants, especially if sustained over many years; (b) frequent urination, which can be both inconvenient and embarrassing; (c) expense, for those who satisfy the 8 x 8 requirements with bottled water; and (d) feelings of guilt for not achieving 8 x 8.
Other claims discredited by scientific evidence that Valtin discusses include:
Thirst Is Too Late. It is often stated that by the time people are thirsty, they are already dehydrated. On the contrary, thirst begins when the concentration of blood (an accurate indicator of our state of hydration) has risen by less than two percent, whereas most experts would define dehydration as beginning when that concentration has risen by at least five percent.
Dark Urine Means Dehydration. At normal urinary volume and color, the concentration of the blood is within the normal range and nowhere near the values that are seen in meaningful dehydration. Therefore, the warning that dark urine reflects dehydration is alarmist and false in most instances.
Is there scientific documentation that we do not need to drink "8 x 8"? There is highly suggestive evidence, says Valtin. First is the voluminous scientific literature on the efficacy of the osmoregulatory system that maintains water balance through the antidiuretic hormone and thirst. Second, published surveys document that the mean daily fluid intake of thousands of presumably healthy humans is less than the roughly two quarts prescribed by 8 x 8. Valtin argues that, in view of this evidence, the burden of proof that everyone needs 8 x 8 should fall on those who persist in advocating the high fluid intake without, apparently, citing any scientific support.
Finally, strong evidence now indicates that not all of the prescribed fluid need be in the form of water. Careful peer-reviewed experiments have shown that caffeinated drinks should indeed count toward the daily fluid intake in the vast majority of persons. To a lesser extent, the same probably can be said for dilute alcoholic beverages, such as beer, if taken in moderation.
"Thus, I have found no scientific proof that absolutely every person must 'drink at least eight glasses of water a day'," says Valtin. While there is some evidence that the risk of certain diseases can be lowered by high water intake, the quantities needed for this beneficial effect may be less than 8 x 8, and the recommendation can be limited to those particularly susceptible to the diseases in question.
you have lost a ton of weight. what is your stance on this? how much do you drink per day?0 -
Despite some interesting claims, I can tell the difference in my own body when I don't get enough water. I retain water and get bloated if I don't stay well hydrated. On days I don't drink enough I am sluggish and unmotivated. My skin gets dry faster if I'm not properly hydrated, and my muscles stay sore longer.
Just because a few people have found evidence that it is not necessary to drink your water, it doesn't outweigh the many more who clearly outline the benefits to drinking the big 8.0 -
A main argument I make about drinking water vs. drinking pop/juice/etc. is that water is 0 calories... yeah, 0 calories! Why waste your daily calories on beverages!? On top of that... water doesn't have nasty added chemicals that have been shown to slow metabolism, spike insulin and cause tooth decay (yes, even diet sodas)... and water doesn't dehydrate you (like sodas and other beverages), but rather, it hydrates you!
So, I say again... sure, sharing articles is GREAT, but trying to find excuses to not drink enough water isn't... maybe I sound harsh, but I've gone through years of learning stuff the hard way... so I'm very passionate about what I've learned.0 -
I agree, I need 6-8 glasses of water, or I do retain, and I feel better when I drink all my waters0
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Despite what these two article writers may say... I'll stick with the official guidelines actually set into place by the American College of Sports Medicine. Somehow, I'd think that they are a more valid source
I hope nobody reads these just for an excuse to not drink water and chug diet Coke instead... I mean, seriously, people...
How'd you know what I was thinking? But it's diet pepsi, not coke:bigsmile:0 -
From my Oncologist to My Internist have all advised me too much water can flush nutrients out of your body. I drink 6-8 glasses to avoid getting a headache. And on hot days and after hard work out... a little more. I don't drink any diet soda. I have girlfriends that live on Diet Coke and they constantly suffer from Urinary track and Kidney Infections, poor skin, and fatigue. No thanks!0
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:laugh:How'd you know what I was thinking? But it's diet pepsi, not coke
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It's funny. My doctor told me that drinking 8 glasses a day is unnecessary and that you should drink when you're thirsty (although sometimes we mistake thirst for hunger so always go for some water first). He said drinking 8 glasses a day doesn't hurt you though, so if it makes you feel like you're really doing something sometimes the placebo affect is more effective than the actual science behind it all.0
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I drink the 64 oz. I do daily because I'm thirsty for it, I figure my body must know better than I do, and it's telling me something. Even when I'm not even trying to, I drink that much. I always have.
:drinker: :drinker: :drinker: :drinker: :drinker: :drinker: :drinker: :drinker: :drinker: :drinker:
Here's to H20!0 -
I make sure to drink plenty of liquids and I've seriously cut back on the diet sodas due to the phosphates. I also have had to learn the difference between thirst and hunger as I do think that plays a serious role in weight gain. I don't have a problem drinking juice, tea, or crystal light in place of water. I just don't see where that's a problem and I feel fine and am losing weight so, why fix it if it aint broke........
But, Here's why I bought this up.
When I was a kid, many moons ago, we would run around outdoors riding bikes and playing games for hour after hour on end and never had a water bottle with us. Even in high school, you never saw athletes chugging water every five minutes. When I was in college, no-one showed up to class with water bottles attached to their hips. Despite all that, I can't remember a single person every being hospitalized or even ill from dehydration.
A few years ago the bottling companies started selling bottled water and it's crazy expensive. I mean, honestly , if you're buying from a vending machine you are paying about $1 for 20 oz of water that is probably no purer than what you can get from your kitchen sink. Really! When did we start thinking it was ok to pay more for water than we do for gasoline?
How much has has marketing contributed to the water craze in America? I just have to wonder.0 -
I make sure to drink plenty of liquids and I've seriously cut back on the diet sodas due to the phosphates. I also have had to learn the difference between thirst and hunger as I do think that plays a serious role in weight gain. I don't have a problem drinking juice, tea, or crystal light in place of water. I just don't see where that's a problem and I feel fine and am losing weight so, why fix it if it aint broke........
But, Here's why I bought this up.
When I was a kid, many moons ago, we would run around outdoors riding bikes and playing games for hour after hour on end and never had a water bottle with us. Even in high school, you never saw athletes chugging water every five minutes. When I was in college, no-one showed up to class with water bottles attached to their hips. Despite all that, I can't remember a single person every being hospitalized or even ill from dehydration.
A few years ago the bottling companies started selling bottled water and it's crazy expensive. I mean, honestly , if you're buying from a vending machine you are paying about $1 for 20 oz of water that is probably no purer than what you can get from your kitchen sink. Really! When did we start thinking it was ok to pay more for water than we do for gasoline?
How much has has marketing contributed to the water craze in America? I just have to wonder.
I agree with you there, remember Dateline testing the top 10 bottled waters and NY's city had a healthier water from their public supply? :huh: :huh: :huh:
It is bad for the enviroment, all those wasted plastic bottles...sheesh. I have a water filter on our kitchen sink and fill up nondisposable 20 oz. bottles every night after dishes. If I'm out and about I will break down if I have to, but usually I tilt one in the freezer to it's half ice and fill up with cold water to take with me on shopping trips or whatever.0 -
I think this is an interesting topic because I do like to challenge the anecdotal advice that seems to just float around and make things harder for us. "Don't eat after ____. Don't eat carbs after ____. Drink ____ water. Eat every _____ hours." A lot of it has either been disproved or just never tested.
The kidneys actually function based on blood pressure, not water levels. Everything small enough to be filtered is filtered by being squeezed through something like a garlic press. Your blood pressure actually determines how much water you retain or pass, so actually your kidneys control the water, not the other way around.0 -
To be honest...
i have lost 65 lbs so far and i have not changed my water intake.. i always like water and i drink it when im thristy.. that means while i eat and work out.. or other times like shopping makes me very thristy.
and i have lost all the weight just fine.. my pee is yellow in the morning and clear the rest of the day (sorry if that was too much info :sick: ) i've read all to pro and cons of it and decided that i needed not too worry... my body will tell me if im thristy ..
that was my 2 cents....0 -
Thanks for this interesting information. I admit that I have felt guilty when I only have a glass of water some days, it's good to know that the 8 glass a day rule has no facts to back it up.
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