Today’s stone age: How to eat to prevent kidney stones
Kidney stones are very common: Men have a nearly one in five chance of developing kidney stones over their lifetime, and women have a nearly one in 10 chance. And as part of what is known as the “Kidney Stone Belt,” D.C.-area residents are at even higher risk of developing kidney stones.
This is a major problem, and it’s one that’s only gotten worse with time. The overall risk for kidney stones in the late 1970s was calculated at 3.8 percent. In the late 2000s, that number had jumped to 8.8 percent. That’s more than a 231 percent increase in the overall risk of kidney stones in just 30 years.
If you have one kidney stone, the chances of developing a second one or more over your lifetime are more than 50 percent. And having kidney stones also can put you at greater risk for long-lasting problems such as kidney failure, recurrent infections, and multiple other conditions.
Fortunately, making smart dietary choices can prevent kidney stones from developing in the first place. And if you develop a kidney stone, we can determine what’s causing it and lower your risk for developing another one.
LISTEN: Dr. Daniel Marchalik discusses kidney stones in this Medical Intel podcast.
A formula for kidney stone protection: Drink enough water
Dehydration is the biggest risk factor for kidney stones that most people face. Our kidneys filter blood to remove waste products. These waste products enter our bloodstream from what we eat and drink. When urine is more concentrated, it’s more likely that the waste products filtered out by the kidneys will form a stone. The darker yellow urine is, the more concentrated it is. Urine should be light yellow or clear if you’re getting enough to drink.
Sadly, most of us don’t get enough to drink. Kidney stones tend to be more common in areas of the world with warmer temperatures, where the heat makes it easier to get dehydrated. We call this the “Kidney Stone Belt,” and it includes Maryland, Virginia and Washington, D.C., among other places.
The simple answer for dehydration is to drink more. Water is best, of course. Citrus fruits like lemon can lower the risk for kidney stones because they contain a compound called citrate. Therefore, adding lemon to water or drinking lemonade also can help.
Of course, drinking more water is easier for some people than others. I’ve seen patients who come in with kidney stones, and they tell me, “I have no idea what my risk factor is.” Then I find out they don’t drink water all day because they can’t go to the bathroom during the workday.
Avoid soda and other drinks that are high in sugar when possible. Sugar alters the way the body absorbs minerals and can increase the risk for kidney stones. Sugar also increases the acid levels of urine, which makes stones more likely to form.
A diet to prevent kidney stones: They are what we eat
It’s not just the amount of fluid in urine that determines a person’s risk of kidney stones. This risk also is based on the amount of waste products the kidneys have to filter from the blood. When there are more of certain types of waste products relative to the amount of fluid in urine, the risk of kidney stones goes up.
One of the reasons our risk for kidney stones has increased so much since the 1970s is because our diets have changed since that time. Two of the main dietary culprits for kidney stones are proteins and salt.
The modern American diet contains a lot more protein than it did in the 1970s, especially animal-based protein. We consume animal-based protein in the form of:
- Chicken and other poultry
- Red meat
I tell my patients to limit their protein intake to two servings per day. That takes some planning and thought about what you eat. If you know you’re having fish for dinner, and you had sausage with breakfast, avoiding that chicken-salad sandwich for lunch is one way to control your protein.
The salt, or sodium, that we eat plays a huge role in the formation of kidney stones. Since the 1970s, a lot more of the food we eat is processed and packaged, and that means more salt. Plus, people are eating saltier foods and more of them.
For example, just 1 ounce of potato chips can have about seven to 10 percent of the average person’s daily recommended maximum serving of salt. And as the U.S. Department of Agriculture notes, an average single-patty plain cheeseburger at a fast-food restaurant has 469 milligrams of salt—more than 20 percent of the maximum daily serving of 2,300 milligrams per day.
That would be bad enough if people stuck to the upper limits of salt intake per day. But most people eat much more salt than the recommended maximum amount. As noted by the U.S. Department of Health and Human Services, the average woman consumes 2,980 milligrams of salt per day. And the average man consumes 4,240 milligrams of salt per day—nearly twice the recommended maximum. So people are putting tremendous loads of salt into their systems, and the kidneys have to filter all of that salt out.
Everyone can decrease the amount of salt in their diet. Salt is such a prevalent ingredient in food, even when you might not expect it. Most of the salt we eat comes from commercial food processing operations. And it can be found in unexpected places: ketchup, cereal, tomato sauce, bread and canned vegetables have some of the highest salt contents of our everyday food. Pay attention to the nutrition information on packaged foods, and choose low-sodium or no-sodium options when possible.
When you cook, limit the amount of salt you use in your recipes. Fresh herbs, pepper and other ingredients can add flavor to dishes without the need for a lot of salt.
When to treat kidney stones and reducing future risk
It’s not always possible to avoid kidney stones. Request an appointment with one of our urologists if you notice the following symptoms:
- Changes in your urine’s color or appearance
- Nausea or vomiting that doesn’t go away
- Sharp pain in the side or mid-back
Related reading: Kidney stone diagnosis and treatment
When I see patients for kidney stones, I use imaging studies to get a look at where the stone is and how big it is. Not every stone needs surgery. If you have a small stone, it’s probably one we can keep a close watch on with regular visits to make sure it passes on its own. If it’s a large stone that’s blocking the ureter (the tube that lets urine pass from the kidney to the bladder), it probably needs to be treated. Without treatment, those kinds of stones can lead to permanent kidney damage if they don’t pass on their own.
For some doctors, treatment stops as soon as the stone is gone. But that’s not how we should treat patients with kidney stones. As we know, more than half of the patients who develop a stone will have another stone in their lifetime. Therefore, as with any other chronic disease, we work to figure out why the patient has the problem and what we can do to fix it, and that’s how I treat kidney stones.
The process starts with a basic blood draw, called a BMP, which stands for basic metabolic panel. This shows us the basic chemistry of your blood, including levels of sodium, potassium, calcium and other substances.
Then we do a 24-hour urine collection, which involves taking all of the urine a patient produces for 24 hours and sending it to a lab for analysis. We look for the same factors in the patient’s urine as we do in the blood and compare the levels. If a patient has low levels of citrate in their urine, we know to increase the patient’s citrate levels. Chances are, that’s going to help you not make more kidney stones in the future. This is a personalized process based on each patient’s unique factors.
Kidney stones may be little, but they’re a big problem for our country. Making smart choices about what goes into your body can reduce your risk for the pain and consequences of kidney diseases down the road.