Many people regularly consume a lot of water and other fluids daily believing it is healthy. A recent Canadian community study found that 4.4% of the people had protein in their urine and yet had no known risk factors for kidney damage such as hypertension or diabetes. These people were producing more than 6 pints of urine a day due to drinking a lot of water and/or other fluids. On average they were drinking more than 8 pints of fluids daily. Most said they were doing so because they believed it to be healthy to drink a lot of water. The researchers asked them to limit their fluid intake to no more than 4 pints per day for one week. As a result, the amount of protein in their urine dropped by more than half.1The myth that people should drink at least 8 glasses of water a day apparently started back in 1945 when the U.S. Nutrition Council recommended people consume 8 glasses of fluid a day. However, except perhaps for people with kidney stones there is little reason to believe drinking more water than thirst demands is healthy. Earlier research has shown that water loading in people with healthy kidneys can lead to the loss of protein and there is also evidence that those with poor kidney function see more rapid declines in renal function when fluid intake is high. From 1988 to 2004 the incidence of chronic renal disease increased from 10% to 13% of the US population. The earliest signs of chronic kidney disease are a reduction in the ability of the kidney to clear creatinine from the blood and/or the loss of small amounts of blood proteins in the urine. It is possible that excessive water drinking may be playing a role in the development of chronic kidney disease.Bottom Line: To reduce one’s risk of chronic renal failure and to slow the progression of the disease, it is important to prevent or reverse hypertension, insulin resistance and type 2 diabetes, and lose excess body weight. This is best accomplished by adopting a diet low in salt, high in fruits, vegetables and whole grains and a moderate amount of seafood and nonfat dairy. It may be helpful to tell those with protein in their urine with otherwise normal kidney function to limit fluid intake to the amount needed to quench thirst.By James J. Kenney, PhD, RD, FACN1 Can Med Assoc J 2008;178:173-5