By Rakesh Khanna, MD
In the United States, kidney stones are a common health problem that will affect nearly one in 11 individuals at some point in their lifetime — and the prevalence is increasing. On top of that, if you have had a stone episode, you’re at high risk of having another. It is estimated that the risk of recurrence is 50 percent within 10 years.
Given how common stones are, how painful they are, what can we do to prevent kidney stones? If I have already had a stone episode, what can I do to prevent another one?
The first thing to do is drink a lot of fluid. The components that make up stones are present in the urine. The more dilute the urine is, the less likely these components will come together and form stones. The goal is to maintain a urine output of at least 2.5 liters a day. That means you have to drink at least 2.5 liters a day and if you are physically active and sweating a lot, in effect you actually need to drink a lot more.
Most types of fluid are OK to drink. The exception is probably cola. One study showed that those who reduced their cola consumption had a lower stone risk as compared to those who did not. It’s also important to try to drink fluids throughout the day and not just at one point in time — in other words, it’s better to have a glass of water every hour during the day, instead of eight glasses of water in the evening. In the first case, the urine is likely to be dilute throughout the course of the day, whereas in the second the urine will be very dilute in the evening but will be very concentrated in the daytime.
For most people, their urine tends to be most concentrated in the morning when they wake up (they have been sleeping so they are not drinking any fluids). So, if you happen to get up for whatever reason, before going back to bed, have a glass of water.
The second thing to do is to limit sodium intake in your diet. The goal is to limit to less than 2,300 mg daily. This is not only important to prevent recurrent stones, but it is also important if you have high blood pressure which is an important risk factor for heart disease.
If you know your stone is composed of calcium oxalate (this is the most common stone type), you should try to limit your intake of oxalate-rich foods. Some common examples are spinach, potatoes, and nuts. This is not easy because oxalate is found in a lot of foods (a list of foods can be found on the internet). While low oxalate alternatives do exist, it can be quite difficult to remain on a low oxalate diet. All you can do is try your best.
You should not restrict calcium intake, unless the levels of calcium in the urine are high (this can only be determined through lab testing). Lowering your calcium intake actually results in a higher stone risk.
Citrate is a crucial molecule that blocks calcium stone formation. Low citrate levels are a common risk factor for stone disease. A diet high in fruit and vegetables can increase urinary citrate levels. Conversely, a diet high in non-dairy animal protein is a double insult to your body: not only is it an acid load on your body (this will use up your citrate, therefore result in lower levels, and increase your stone risk), it can also increase levels of uric acid in your urine which is stone forming substance and increase your stone risk! It is a double insult.
I hope this overview is helpful. Please take care of yourself. Poet and Pulitzer Prize winning Edna St. Vincent Millay once wrote “It’s not true that life is one damn thing after another—it’s one damn thing over and over.”
Rakesh Khanna is a urologist with Upstate Urology, Upstate Medical University.