Commentary On The Controversy Over
How Much Water To Drink
Michael Garko, Ph.D.
Host – Let’s Talk Nutrition
“Water is the best of all things” (Pindar, C. 522- C. 438 B.C.). Decades worth of exhortations by more than a few healthcare experts, nutritionists and dieticians to drink at least eight 8 oz. glasses of water daily and over nine billion gallons of bottled water consumed annually in just the United States equating to a consumption rate of 27.6 gallons of bottled water per person per year (Beverage Marketing Corporation, 2006) would seem to suggest that there is considerable agreement with the ancient Greek lyric poet, Pindar, and his description of water in his Olympian Odes.
Although they did not challenge Pindar’s belief about water being “the best of all things, Negoianu and Goldfarb (2008), two medical doctors from the Renal, Electrolyte, and Hypertension Division of the University of Pennsylvania, did challenge the validity of five health claims associated with drinking eight 8 oz. glasses of water a day, known as the 8 X 8 rule.
The May, 2008, issue of Healthful Hints serves as a commentary on Negoianu and Goldfarb’s conclusion that presently there is no clear research evidence to support the claim of achieving a health benefit from drinking increased amounts of water, generally, and following the classic recommendation of drinking eight 8 oz. glasses of water daily, specifically.
Negoianu and Goldfarb’s Argument
Negoianu and Goldfarb (2008) zero in on five specific health claims about drinking water. They argue the claims are unsupported by solid scientific evidence and suggest they are especially promoted on the Internet to the extent the claims have become urban legends or myths, believed and followed as if they were true.
First, there is the claim that increased or supplemental water intake can improve kidney function and cleanse the body of toxins. According to Negoianu and Goldfarb (2008), the kidneys rely on several mechanisms such as glomerular filtration, tubular secretion and degradative metabolic pathways to clear toxins from the body. They point out that while increased water intake may have some impact on the renal clearance of some substances (e.g., sodium & urea), “little is known about the identity of toxic substances cleared by the kidney” (Negoianu & Goldfarb, 2008, p. 1) and existing study data cannot conclusively show that drinking excess water will assist the kidneys in removing excess toxins.
Second, there is the assertion that ingesting supplemental water will be retained in organs of the body and improves their functioning. Negoianu and Goldfarb (2008) argue that for this claim to be true it would first have to be shown that people who are in an ideal state of water retention will hold on to additional ingested water rather than just excreting it in their urine. Furthermore, they contend that water retention is quite variable and depends, for example, on the rate at which water is ingested. That is, if water is ingested over a 15 minute period it is mostly excreted, while water ingested slowly over a 2.5 hour period is mostly retained. Therefore, those gulping their water would not necessarily experience improved organ functioning. For those who take their time, there is a question as to whether they would experience improved organ function because there are no data to demonstrate “what type of steady state develops over longer periods of increased water intake” (Negoianu & Goldfarb, 2008, p. 2).
Third, one of the most popular claims associated with increased water intake is that supplemental water results in increased satiety or a feeling of fullness. Supporters of the 8 X 8 rule often make this claim within the context of the overweight-obesity epidemic and contend that ingesting supplemental water will help curb one’s appetite. Negoianu and Goldfarb (2008) argue that none of the existing studies examining the relationship between increased water intake and decreased calorie intake “makes clear whether drinking a large volume of fluid over the course of a day will decrease the number of ingested calories” (p. 2).
Fourth, Negoianu and Goldfarb (2008) call attention to the claim that headaches result from water deprivation. However, notwithstanding one non-conclusive trial examining the effect of increased water intake on headache prevention, they point out there is little research to support what they would consider to be an urban myth.
Fifth, the Internet is replete with articles claiming the cosmetic benefit of improved skin tone from drinking supplemental water. Negoianu and Goldfarb (2008) state that although dehydration can decrease skin turgor, “it is not clear what benefit drinking extra water has for skin” (p. 2).
Negoianu and Goldfarb’s (2008) conclude that “there is no clear evidence of benefit from drinking increased amounts of water” (p. 2) and the 8 X 8 rule, especially when it comes to the five health claims about ingesting supplemental water.
Comment on Negoianu and Goldfarb’s Argument
There were many who became upset when Negoianu and Goldfarb’s (2008) editorial was published. However, Drs. Negoianu and Goldfarb are not attempting to minimize the importance of water and send the message that drinking water is unimportant to sustaining good health and preventing disease. Instead, they are challenging whether ingesting increased amounts of water truly result in the sort of claimed health benefits touted on the Internet, periodicals, books and health talk radio and television shows. They recognize that humans cannot survive for more than a few days without water and there are medical dangers associated with hypertonicity and volume depletion. They also believe that “individuals in hot, dry climates have increased need for water, as do people who engage in strenuous physical exertion” (Negoianu & Goldfarb, 2008, p. 1).
Furthermore, although they conclude there is no clear evidence pointing to real health benefits of supplemental water ingestion, Negoianu and Goldfarb (2008) admit “there is also no clear evidence of lack of benefit. In fact, there is simply a lack of evidence in general” (p. 2). In a real sense, Negoianu and Goldfarb (2008) have thrown down the gauntlet for researchers to determine how much water should be consumed daily and what health benefits can be gleaned from supplemental water intake. It is better for health consumers if a body of research is developed to show that supplemental water ingestion and the 8 x 8 rule can (1) improve kidney function and cleanse the body of toxins, (2) improve organ function, (3) create satiety and control calorie intake, (4) prevent headaches and (5) enhance skin tone, among other health outcomes.
In the meantime and until researchers confirm the various claims about supplemental water intake, it would be healthy and wise for people to continue drinking sufficient amounts of water to the extent that they allow their body to carry out effectively its metabolic and physiologic functions and prevent themselves from becoming dehydrated. If you generally feel better and healthier following the 8 X 8 rule or in fact drink more water than that on a daily basis and are experiencing any of the health benefits discussed above from your current level of daily water consumption, then you might want to continue doing the same.
Each person has his/her own water consumption requirement and should exercise common sense in how much water is consumed on a daily basis. Following the 8 X 8 rule is not reported in the literature to be an unhealthy nutritional practice, especially for people living in hot and dry climates, athletes, outside workers and those who live a physically active lifestyle. In fact, some people may require more than eight 8 oz. glasses of water a day and should consume an amount of water which prevents dehydration.
Beyond the issue of quantity of water consumed on a daily basis there is the issue of quality of water. Given the level of water contamination, it is recommended that purified drinking water be consumed, while distilled water (which contains no minerals and can leach them from the body) and tap water (i.e., water derived from surface reservoirs formed from potentially contaminated rivers, streams, lakes or groundwater) be avoided. Also, for those drinking well water and spring water, they should be mindful of the fact these sources can also be contaminated with various toxic chemicals (e.g., lead, mercury, cadmium, copper, aluminum, arsenic, platinum, etc.), pesticides, herbicides, bacteria, viruses, parasites, etc. as are the water sources for tap water. My preference is to drink water filtered or purified by reverse osmosis. Many experts believe this is the best way to purify water.
Finally, it is important to remember that water is second only to air for sustaining human life and should be a primary component of any person’s nutritional and dietary plan. Drink up and be healthy.
Beverage Marketing Corporation. Beverage Marketing Corporation 2006 Statistics. Retrieved April 22, 2008 from http://www.bottledwater.org/public/Stats_2006.doc.
Negoianu, D & Goldfarb, S. (2008). Just add water. Journal of the American Society of Nephrology, 19, 1-2.