Are There Health Benefits in Drinking Increased Amounts of Water?

Two University of Pennsylvania doctors, after an extensive review of literature, say there is no scientific evidence establishing the need for the average healthy person to drink increased amounts of water. Their recommendation: “Drink when you’re thirsty. That’s the way your body is designed.” According to the study entitled “Just Add Water,” increased water intake is only really justified in certain cases, such as for athletes or those engaged in vigorous exercise, those living in hot, dry climates, and people suffering from particular illnesses.

Dr. Stanley Goldfarb, a kidney specialist, and his colleague Dr. Dan Negoianu, both with the Renal, Electrolyte and Hypertension Division at the University of Pennsylvania in Philadelphia, scoured literature on the benefits of drinking water. In the U.S., it is a long held belief that drinking the recommended eight glasses of water per day is essential for everyone. Water has been touted to be helpful not only in removing toxic chemicals from the body and keeping organs in top condition, but for stopping headaches, keeping weight off, and even improving skin tone.

The doctors examined the theory that drinking more water helped the kidneys flush more toxins from the body. They found that while drinking more water does have an impact of the rate at which various substances are cleared by the kidney, there is no indication that this resulted in any actual health benefits. In a radio interview, Dr. Goldfarb said that drinking large amounts of water actually tends to reduce the filtering ability of the kidney. They also found no documentation that an increased amount of water is beneficial to the body’s organs, regardless of whether it is gulped or slowly ingested.

The doctors searched for evidence that headaches could be attributed to water deprivation. They found one small study in which trial participants who drank more water experienced fewer headaches than those who did not, but the statistics were not significant.

Water is supposedly an ideal aid for those who want to lose weight, creating a sense of fullness, thus curbing the appetite. The doctors found the clinical evidence in this case to be inconclusive. Dr. Goldfarb said that while some studies suggested that calorie intake was reduced in those given water prior to meals; other studies suggested that it wasn’t. The doctors found no clinical trials measuring the effects of water intake on weight maintenance.

The doctors also reviewed literature relating to water and skin tone. They said that while dehydration can decrease skin tension, no studies were found that showed a clinical benefit to skin tone with increased water intake.

The doctors added that, in certain cases, drinking a lot of water may actually be harmful. Dr. Goldfarb cited the case of a woman who, as part of a contest, drank water continuously and very rapidly for several minutes. Shortly afterward, she developed swelling of the brain and died.

An earlier study by Heinz Valtin from Dartmouth also debunked the 8x8 water recommendation (8 ounces, 8 times a day), as well as a few other myths; dark urine does not mean dehydration, thirst doesn’t mean “it’s too late,” water doesn’t help or prevent constipation, cancer or heart disease, and caffeinated beverages count as fluid intake.

Dr. Goldfarb says there is no rational basis for the widespread belief that people need to drink eight glasses of water a day, and isn’t clear where the recommendation comes from. But Valtin speculates that our obsession with water may have evolved from The Food and Nutritional Board of the National Research Council who, in 1945 wrote that “an ordinary standard for diverse persons is 1 milliliter for each calorie of food.” This would amount to about 2-2.5 liters, or 64-80 ounces per day. However, eager readers may have stopped short before reading the sentence noting that “most of this quantity is contained in prepared foods.”

On the other hand, Dr.’s Goldfarb and Negoianu conceded that “there is also no clear evidence of lack of benefit.” Dr. Goldfarb suggests there may even be a placebo effect to those eight daily glasses. He says if you are convinced that a lot of water makes you feel stronger and healthier, so be it. However, he also notes that people who don’t feel that way should not feel obligated to do so.

The study will be published in the June issue of the Journal of the American Society of Nephrology.