Q: What can I do to prevent kidney stones?

A: Kidney stones are crystallized compounds that occur within the urinary tract when calcium combines with certain minerals that are present in your urine. The most common mineral is oxalate, which is naturally found in certain foods. According to the World Journal of Urology, calcium-oxalate stones are the most common form of kidney stone, making up nearly 80 percent of all cases in the United States.

Who is at high risk of getting kidney stones?

  • Men are at higher risk than women.
  • Anyone with a family history of kidney stones.
  • Anyone who has previously had a kidney stone.
  • People who are obese, meaning a BMI greater than 30.
  • People with an inflammatory bowel disease such as Crohn's.
  • Gastric bypass surgery patients. (The body absorbs less calcium after gastric bypass procedures.)

Here's how to avoid forming a calcium-oxalate kidney stone:

1. Drink enough fluids throughout the day. This is especially important during the summer, when kidney stones are more apt to develop due to dehydration. Staying hydrated keeps waste flowing through your body and allows it to exit through urination. Adequate intake of fluids also helps to thin out your urine so that it's more difficult for mineral build up and crystallization to occur.

I recommend that adults consume one ounce of fluid per two pounds of body weight daily. For example, a 140-pound female should consume 70 ounces of fluid a day. Note that not all fluids are created equal. Coffee, iced tea, and many sodas contain caffeine, which can cause dehydration if consumed in excess. Soda contributes to the buildup of calcium oxalate so it is best to avoid entirely if this is a concern.

2. Shake your salt habit. Excess sodium intake from the salt shaker, fast foods, or daily consumption of canned products or deli meats raises the amount of calcium in your urine, which, in turn, causes oxalate to bind with the excess calcium in the urine. Adults with hypertension, prehypertension, or a history of kidney stones should limit sodium intake to 1,500 mg a day.

3. Limit high oxalate foods. Foods such as spinach, rhubarb, sweet potato, beets, chocolate, kale and peanuts contain high amounts of oxalate.

In addition, consuming animal proteins such as beef, cheese, eggs, pork and fish in excess may contribute to crystallization of uric acid due to their purine content. Consider cutting your animal protein intake by 30 percent. I recommend eating a vegetarian diet twice a week by replacing some of the animal protein you would typically eat with beans, dried peas, and lentils, all plant-based foods that are high in protein and low in oxalate.

4. Monitor added sugars. Added sugars, especially in the form of high fructose corn syrup, contribute to uric acid crystallization. Natural sugars in fruits are perfectly fine to consume daily.

The American Heart Association recommends females limit added sugar intake to less than six teaspoons a day (24 grams). Males are recommended to limit added sugar intake to less than nine teaspoons a day (36 grams). Read labels.

5. Avoid vitamin C supplements unless your health-care provider or dietitian has advised you otherwise. Excessive amounts of vitamin C (more than 500 mg a day) may cause higher amounts of oxalate. Since vitamin C can be naturally obtained through diet, supplementation is most often not necessary.

6. Don't be afraid of calcium. A diet low in calcium actually increases one's risk of developing kidney stones, so don't reduce your calcium intake. Instead, aim to eat and drink calcium and oxalate-rich foods together during a meal. In doing so, oxalate and calcium are more likely to bind to one another in the stomach and intestines before the kidneys begin processing, making it less likely that kidney stones will form.

7. Consider seeking weight-loss management counseling. There is a strong association between overweight and obese individuals and the incidence of kidney stones. A dietitian who specializes in kidney stone prevention can help you plan meals to reduce the incidence of kidney stones.

Theresa Shank, RD, LDN, is a Philadelphia-based registered dietitian and the founder of Philly Dietitian.