Kidney stones are masses of minerals, typically calcium and oxalate, that become lodged in your urinary tract. Usually, compounds in your urine inhibit these crystals from forming.
Some people form stones when their urine contains more crystal-forming substances, such as calcium and uric acid, than the available fluid can dilute. If the stone is large enough to cause irritation or blockage, severe pain will typically result. The pain may shift to different locations and change in intensity as the stones move about. Other symptoms of kidney stones include:2
|Severe pain in the side and back, below the ribs
||Pain that spreads to the lower abdomen and groin
||Pain that comes in waves and fluctuates in intensity
|Pain on urination
||Pink, red, or brown urine
||Cloudy or foul-smelling urine
|Nausea and vomiting
||Persistent need to urinate
||Urinating more often than usual
|Fever and chills if an infection is present
||Urinating small amounts of urine
What makes some people more prone to developing kidney stones than others? There are some surprising risk factors to be aware of, recently compiled by TIME:3
1. Not Enough Calcium
Most kidney stones are made out of calcium, so it would seem that consuming too much could be problematic. On the contrary, people eating a low-calcium diet are more likely to develop kidney stones than those consuming more calcium.4
It turns out that calcium in your digestive tract binds to chemicals called oxalates from your food, preventing them from entering your bloodstream and urinary tract where they may form kidney stones.5
It is important to note that it is the calcium from foods that is beneficial – not calcium supplements, which have actually been found to increase your risk of kidney stones by 20 percent.6
2. An Obsession with Leafy Greens
Leafy greens, particularly spinach, are high in oxalates. These chemicals bind with calcium and should be excreted via your urinary tract, but if their concentrations become elevated they can concentrate in your urine and form kidney stones.
Leafy greens are clearly among the healthiest foods you can eat, but if you struggle with kidney stones you might want to swap higher oxalate greens like spinach, for lower-oxalate options, like kale.
3. Too Much Processed Salt
Salt, particularly unprocessed natural varieties, has been unfairly targeted as a root source of chronic disease. However, excess sodium intake can increase the amount of calcium excreted by your kidneys, which in turn may increase your risk of kidney stones.
You needn’t shun a sprinkle of unprocessed salt added to your meals here and there. Rather, cut out the majority of processed foods in your diet, which is where most processed salt is hidden.
4. Too Little Citrus (and Veggies of All Kinds)
Citrus fruits contain citrate, a compound that may lower your risk of kidney stones. Simply adding a squirt of lemon or lime to your water may therefore be helpful, although you can also increase your intake of fruits and vegetables across the board.
One study found people who normally avoided produce could decrease levels of kidney-stone-causing chemicals in their urine by increasing their produce intake for one month.7 Eating plenty of vegetables helps ensure you’re getting enough magnesium, which is also beneficial.
Magnesium plays an important role in your body's absorption and assimilation of calcium, as if you consume too much calcium without adequate magnesium, the excess calcium can actually become toxic and contribute to health conditions like kidney stones.
5. Too Much Iced Tea
Black tea is a rich source of oxalate, so overconsumption may increase your risk of stone formation. Earlier this year, the New England Journal of Medicine reported the case of one 56-year-old man who was drinking 16 eight-ounce glasses of iced tea daily. He was admitted to the hospital for kidney failure and was found to have “abundant calcium oxalate crystals” in his urine.8
6. Drinking Soda
Drinking soda is associated with kidney stones, possibly because the phosphorus acid it contains acidifies your urine, which promotes stone formation. In addition, one South African study found that drinking soda exacerbates conditions in your urine that lead to formation of calcium oxalate kidney stone problems.9
The sugar, including fructose (and high fructose corn syrup in soda), is also problematic. A diet high in sugar can set you up for kidney stones, since sugar upsets the mineral relationships in your body by interfering with calcium and magnesium absorption.
The consumption of unhealthy sugars and soda by children is a large factor in why children as young as age 5 are now developing kidney stones. Sugar can also increase kidney size and produce pathological changes in your kidney, such as the formation of kidney stones.
In one study, those with kidney stones who eliminated soda from their diet lowered their risk of recurrence by about 15 percent.10
7. Your Parents
If you have a family history of kidney stones, your risk is increased as well. It’s thought that the inability to efficiently absorb oxalate may be an inherited trait.
8. Inflammatory Bowel Disease (IBD)
If you have IBD, including Crohn’s disease or ulcerative colitis, you’re at an increased risk of kidney stones.11 This could be because such conditions often cause diarrhea, which increases your risk of becoming dehydrated – a major risk factor for kidney stones.
9. Recurrent Urinary Tract Infections (UTIs)
Recurrent UTIs can be a sign of a kidney stone in some cases, as the stones may block the flow of urine, leading to UTIs. If you have frequent UTIs without a known cause, you should get checked out for kidney stones (it’s possible to have one and not know it).
10. Laxative Abuse
Overusing laxatives interferes with your body’s ability to absorb and utilize nutrients, and may lead to an electrolyte imbalance, increasing your risk of kidney stones. Laxative abuse can also cause dehydration, another kidney stone trigger.
11. Migraine Medication
The migraine medication topiramate (Topamax) increases the pH levels in your urinary tract, which may lead to an increased risk of kidney stones.12
Diet wise, women who ate more than 2,200 calories per day increased their risk of kidney stones by up to 42 percent, while obesity also raised the risk. It’s thought that excess weight may lead to changes in your urinary tract that promote the formation of kidney stones. For instance, altered urinary pH levels in people who are obese may increase the risk of uric acid forming kidney stones.
13. Weight Loss Surgery
It should be noted that even though obesity increases kidney stone risk, weight loss surgery that alters your digestive tract actually makes them more common. After weight loss surgery, levels of oxalate are typically much higher (oxalate is the most common type of kidney stone crystal).
The number one risk factor for kidney stones is not drinking enough water. If you aren't drinking enough, your urine will have higher concentrations of substances that can form stones. According to recent guidelines issued by the American College of Physicians (ACP), one of the simplest strategies you can take to avoid kidney stones is to drink more water. According to the National Kidney Foundation:13
“Urine has various wastes dissolved in it. When there is too much waste in too little liquid, crystals begin to form. The crystals attract other elements and join together to form a solid that will get larger unless it is passed out of the body with the urine… In most people, having enough liquid washes them out or other chemicals in urine stop a stone from forming.”
The new ACP guidelines call for people who have had a kidney stone in the past to increase their fluid intake so they have at least two liters of urine per day, which they say could decrease stone recurrence by at least half.14 To achieve this they recommend increased fluid intake spread throughout the day, pointing out that both water and mineral water are beneficial. Research shows, for instance, among patients with kidney stones that those who increase hydration to reach two liters of urine a day had a 12 percent recurrence rate compared to 27 percent among those who didn’t increase their fluid intake.
Additionally, people with high blood pressure may also be at risk for developing kidney stones. However, it's not clear if kidney stones are a cause, or a possible result of hypertension.
The National Kidney Foundation recommends drinking more than 12 glasses of water a day, but a simpler way to know if you are drinking enough water is to check the color of your urine; you want your urine to be a very light, pale yellow (darker urine is more concentrated). Every person's water requirement is different, depending on your particular system and activity level, but simply keeping your urine light yellow will go a long way toward preventing kidney stones.
Remember to increase your water intake whenever you increase your activity and when you're in a warmer climate. If you happen to be taking any multivitamins or B supplements that contain vitamin B2 (riboflavin), the color of your urine will be a very bright, nearly fluorescent yellow and this will not allow you to use the color of your urine as a guide to how well you are hydrated.
More than 1 million Americans visit emergency rooms each year for kidney stones. A recent study suggested that one in nine of them are likely to return for the same problem.15 If you’re experiencing excruciating pain with an unknown cause, it’s a good idea to seek emergency care, although most kidney stones do not require invasive treatment. Small stones may pass with only minimal symptoms and drinking water (up to two or three quarts a day) may help the stones to pass.16
In cases of larger stones that are unable to pass on their own or otherwise causing severe symptoms, treatment may be necessary. Sound waves can be used to break up stones or your doctor may use a scope to locate the stones and then break them up into smaller pieces. Surgery to remove very large stones is also sometimes recommended, but ideally you won’t get to this point.17
Prevention is by far preferable to suffering through a kidney stone episode, so be sure you’re drinking plenty of water, first and foremost. Eating right, including plenty of vegetables and avoiding soda is also important, as is minimizing your intake of other fructose-rich foods (like processed foods and soda). According to The National Kidney Foundation, you should pay particular attention to keeping your fructose levels under control:18
"Eating too much fructose correlates with increasing risk of developing a kidney stone. Fructose can be found in table sugar and high fructose corn syrup. In some individuals, fructose can be metabolized into oxalate."
Finally, be sure you’re getting regular exercise. Even low amounts of exercise may be beneficial to reducing your risk. In a study involving more than 84,000 postmenopausal women, it was found that those who exercised had up to a 31 percent lower risk of kidney stones.19 The link persisted even with only small amounts of physical activity. Specifically, the research showed a lower risk from three hours a week of walking, four hours of light gardening, or just one hour of moderate jogging. You can find my comprehensive exercise recommendations, including how to perform highly recommended high-intensity interval training (HIIT), here.