A kidney stone is exactly that -- a hard mass of minerals and salts that forms in the kidneys. Certain foods and drinks contain chemicals that can lead to these sometimes painful crystals. The stones come in several different types, and foods that are not so good for one kind may be OK to eat if you have another type.
If you’ve had a kidney stone, ask your doctor which it was. That’ll help you know which foods to avoid.
But if you aren’t sure -- or if you just want to be careful about all types of kidney stones -- a good rule is to stay away from too many salty foods and meats and other animal protein.
Calcium Oxalate Stones
More people get this kind than any other. It forms when calcium in your pee combines with oxalate, a chemical that's naturally in many foods.
If you’ve had one of these, watch out for:
High-oxalate foods. Many plants contain oxalate, so it’s hard to avoid it entirely. But some foods have much more than others. Try to limit:
- Almonds and cashews
- Miso soup
- Baked potatoes with skin
- Cocoa powder
- Bran cereals and shredded wheat cereals
- French fries
- Stevia sweeteners
- Sweet potatoes
If you eat or drink calcium-rich foods at the same time, they can help your body handle oxalate without turning it into a kidney stone. So pair your spinach salad with low-fat cheese. Or mix nuts or berries into yogurt. Drinking milk does not cause kidney stones.
Salt. If you eat a lot of sodium, which is an ingredient in salt, that raises the amount of calcium in your urine. Once you finish eating, any extra oxalate “sticks” to calcium in the kidneys. That can produce stones. So limit canned foods, packaged meats, fast foods, and condiments in your diet.
Vitamin C. Too much can make your body produce oxalate. So don’t take more than 500 mg a day.
Calcium Phosphate Stones
These form when calcium in the urine combines with the mineral phosphorus. If you’ve had one of these, you don’t need to worry about oxalate. But do watch for:
Animal protein-rich foods:
- Organ meats, like chicken or beef liver
- Milk, cheese, and other dairy products
Foods that can make urine more alkaline, including:
- Fresh fruit juices (except orange, cranberry, and nectarine)
- Vegetable juices
Processed foods. Phosphorus is a common additive and preservative. So limit fast foods, bottled colas, frozen foods, and luncheon meats. Read the label for ingredients starting with “phos.”
Sodium. Most Americans get too much already. Aim for no more than one teaspoon of table salt a day.
Uric Acid Stones
You get these if your pee is too acidic. These stones contain uric acid, a substance the body produces as it breaks down chemicals in food. Unlike with calcium oxalate and calcium phosphate stones, sodium isn’t a special issue here.
Animal protein. Eating too much red meat, poultry, eggs, and shellfish does two things. It makes your body make more uric acid. And it can rob your system of citrate, a substance that helps keep away kidney stones and maybe keep existing ones from growing.
To get enough protein, you can swap your meat and poultry for:
- Beans, dried peas, lentils, and peanuts
- Soy milk, soy butter, and tofu
- Nuts, like almonds, walnuts, and cashews
Sugary drinks. Tart drinks like lemonade, limeade, and fruit juices are naturally high in citrate that helps keep kidney stones at bay. But hold back on foods and drinks flavored with sugar or, especially, high-fructose corn syrup. They can lead to stones.
These come from a rare condition that runs in families called cystinuria. The disorder causes a natural substance called cystine to leak into your urine. Cystine stones tend to be larger than other types. If you’ve had one, you might have another.
Some issues you can watch for:
Too little water. Drink lots of water to help discourage cystine from forming stones.
Too much acid. Cystine stones grow more easily in acidic pee. That’s the opposite of calcium phosphate stones, which favor alkaline urine. So for this type of stone, curb your hunger for meat and eat more fruits and vegetables, which have lower acid levels.
Sodium: Once again, try not to overindulge on French fries, canned soups, packaged meats, and other salty foods.