December 11, 2010 12:00 AM by Mehmet C. Oz, MD, and Michael F. Roizen, MD
Q: I’ve suffered with kidney stones for 16 years. My most recent attack involved calcium oxalate stones in both kidneys. Do any diets prevent kidney stones altogether?
— Lisa, Ontario, Canada
A: You’re smart to think prevention, because with kidney stones, it’s not always true that “this too shall pass.” Calcium oxalate stones are the most common type. These tough little nuggets form when calcium and oxalic acid combine in acidic pee. Like a hairball in a bathtub drain, a big stone can clog your kidneys or ureter, the tube urine flows through as it travels from kidney to bladder. Your best diet defense? Do the following:
- Drink loads of water to dilute your urine so it’s less acidic. You want to produce about 2 quarts of urine a day.
- Drink lemonade or orange juice, too. They contain citrates, which help stop stones from forming.
- Don’t drink grapefruit juice, cranberry juice, or dark cola. They increase your risk. Avoid salty foods, especially processed meats. (Hot dogs are not your friend.) Sodium increases calcium in urine, where it meets its bad-boy companion, oxalate, and they become hard friends.
- Limit high-oxalate foods, such as spinach, rhubarb, nuts, and wheat bran.
- Don’t limit calcium, but do take calcium supplements with food. The pills may actually be protective because calcium binds with oxalate in food, which keeps it out of your urinary tract.
- If you take vitamin C, limit it to 500 milligrams a day, because C can turn into oxalate in your body. Yes, this supplement could get you “stoned.”
Kidney stones: Preventing kidney stones through diet
The following tips may lower your chance of getting kidney stones:
- The most important thing you can do is drink more fluids, especially water if your doctor says it is okay. Water helps to wash away the substances in the kidneys that could form stones. Try to drink 8 to 10 glasses of water a day. If you don’t already drink that much, slowly increase how much you drink. For example, add one more glass of water each day until you are drinking 8 to 10 glasses a day. This slow increase will give your body time to adjust to the extra fluids. You are drinking enough water when your urine is clear or light yellow. If it is dark yellow, you are not drinking enough fluids.
- If you had a calcium kidney stone, it may help to:
- Eat less salt and salty foods. One way to do this is to not add salt when you cook or eat. Try removing the salt shaker from your table.
- Talk to your doctor or dietitian about how much calcium you need every day. Milk, cheese, and yogurt are all good sources of calcium.
- If you had an oxalate kidney stone, your doctor may ask you to limit certain foods that have a lot of oxalate. You don’t have to give up these foods, just eat or drink less of them. These include:
- Coffee, teas, colas, and chocolate.
- Dark green vegetables, such as spinach.
- Beets, rhubarb, berries, and cranberries.
- Beans and tofu.
- Draft beer.
- Oranges and sweet potatoes.
If you have had kidney stones in the past, it may also help to:
- Eat a balanced diet that is not too high in animal protein. This includes beef, chicken, pork, fish, and eggs. These foods contain a lot of protein, and too much protein may lead to kidney stones. You don’t have to give up these foods. Talk to your doctor or dietitian about how much protein you need and the best way to get it.
- Avoid grapefruit juice.
- Drink lemonade made from real lemons (not lemon flavoring). It is high in citrate, which may help prevent kidney stones.
- Talk to your doctor if you take vitamins or supplements. He or she may want you to limit how much fish liver oil or calcium supplements you take. Also, do not take more than the recommended daily dose of vitamins C and D.
**Note: Some statements are conflicting. Please consult your physician with further questions.