More water doesn’t always slow kidney disease: study

Paul Mayne // Western NewsWestern professors Drs. Susan Huang and William Clark said when it comes to slowing the decline of kidney function for those with chronic kidney disease (CKD), drinking more water may not do the trick, as some previous research suggests.

A new study of water intake among people with chronic kidney disease is literally a “glass-half-full scenario,” said Dr. William Clark.

Clark, professor at the Schulich School of Medicine & Dentistry and a Lawson Health Research Institute scientist, said standard medical advice for people with chronic kidney disease (CKD) is that drinking more water can slow the progression of the disease.

But his latest study, published in the Journal of the American Medical Association, shows there’s no scientific basis for that across-the-board advice.

People with CKD who already drink plenty of water are seeing all the benefit they are likely to get and won’t see better results with higher water intake, the study showed. People who drink little water, however, may find benefit to drinking more.

The kidney’s main job is regulating a person’s internal environment by controlling and filtering the salt and water balance within the body. Clark said kidney disease occurs when the organ’s filtering ability gradually decreases over time, which could lead to dialysis or requiring a transplant.

There are more than 120 potential causes for kidney disease, the most common being high blood pressure and diabetes. Clark said while many claims about the benefits of increased water intake remain untested, a growing body of evidence suggests it improves kidney function through the suppression of the antidiuretic hormone, which helps the kidneys manage the amount of water in your body.

Guided by a successful pilot study, the research team constructed a randomized clinical trial with patients at London Health Sciences Centre, as well as hospitals in Oakville, Windsor, Guelph and Hamilton, to determine if coaching patients to drink more water slowed the decline in their kidney function, compared with those in the control group who were coached to maintain usual fluid intake for one year.

The trial was the largest to date, with more than 630 participants with Stage 3 chronic kidney disease, said Kerri Gallo, nurse project manager for the study.

Most patients with Stage 3 CKD experience few symptoms but have already lost 40 – 70 per cent of kidney function, Gallo said. “Kidney disease often starts slowly and develops without symptoms over a number of years, so it may not be detected until it has progressed to the point where kidney function is quite low.”

The study found, after one year, the increased water consumption did not slow loss of kidney function among patients with high intake.

They did find, however, those with low intake did significantly suppress their antidiuretic hormone release, thus slowing the progression of renal failure.

A previous study, looking at 2,000 people over seven years, showed those with the lowest fluid intake experienced renal decline three times faster than those with high fluid intake.

“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,” said Clark. “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.”

Co-investigator Dr. Susan Huang said the research answers some questions but creates additional ones.

“Perhaps we need to target more specific populations, not just whole general population, where everyone has different causes (to their kidney disease),” said the Western professor and Lawson scientist.

Current treatment guidelines for CKD patients are limited and include the use of medication and optimal blood pressure control, including salt restriction and increased water intake.

“We have no way to actively stop the decline or regain function. Our efforts right now are to slow the progress,” said Gallo.

Perhaps the focus should be on targeting the low water drinkers, the ones where it progression is occurring much more rapidly, said Clark, noting a new two-year study looking at this possibility is soon to get underway. It is really about personalized medicine, he said, how we apply this knowledge to create more targeted treatment approaches.

“Rather than specifically targeting the disease, if you can affect the aging process of the kidney, that will have a much greater impact in terms of reducing renal failure,” said Clark, noting very few diseases are cured, “If we can slow down the progress, so it means your natural life might end before the disease gets you, that is the ideal situation. It’s a glass half-full scenario, but for some, it might be a glass half-empty.”