May 8 (UPI) -- Drinking an extra four to six extra glasses of water per day won't slow the decline of kidney functions for chronic kidney disease patients, according to a study in Britain and Canada.
Researchers with the Lawson Health Research Institute in Ontario and Western University in London studied whether increased hydration made a difference in people with kidney disease. The clinical trial was published Tuesday in the Journal of the American Medical Association.
"Despite widespread beliefs, little scientific data exists on the optimal amount of water to drink," Dr. William Clark, a scientist at Lawson and professor at Western's School of Medicine & Dentistry, said in a Lawson press release. "While many claims about the benefits of increased water intake remain untested, a growing body of evidence suggests that increased water intake improves kidney function through the suppression of the antidiuretic hormone."
Drinking more water is generally advised -- the common advice is to drink eight glasses per day --and has been associated with better kidney function and a reduced risk of kidney stones, but it had not been known whether it can help those with kidney disease.
The randomized clinical trial included 631 patients at London Health Sciences Center and several other hospitals in Ontario with stage 3 kidney disease from April 2013 to June 2017. At stage 3, patients have lost up to 70 percent of their kidney function.
Half of the participants were coached to drink more water -- 1 to 1.5 liters per day, depending on sex and weight. Those in the control group were asked to maintain usual intake or not decrease it by more than one-quarter to a half-liter per day. One liter of water is about 34 fluid ounces.
After one year, the researchers found the increase of water consumption did not slow the loss of kidney function. They found, however, that the reduction significantly suppressed antidiuretic hormone release, particularly when the participant's previous intake was low.
"This research indicates that for most patients with CKD, increasing fluid intake will not stop further loss of kidney function. It does allow us then to focus our efforts on other potential therapeutic options," Clark said. "We do know that many patients are drinking well below the recommended amounts. More research is needed, but the goal would be to tailor increased water intake as a treatment to those patients."
The researchers said they hope to conduct another study with a longer followup.