Should you avoid calcium-rich foods after a kidney stone?

Not automatically. The NIH's National Institute of Diabetes and Digestive and Kidney Diseases says calcium from food, in the right amounts, can block other substances in the digestive tract that may lead to stones.

It sounds backwards. The most common kidney stones are made of calcium oxalate, so many people assume the fix is to cut cheese, milk and other calcium-rich foods. The Cleveland Clinic says that belief is wrong and the opposite of what is currently recommended. Its urologists explain that calcium can neutralize oxalates in your gut, so there is no reason to remove calcium from your diet, even with a history of stones.

The NIDDK makes the same point for people who have had calcium oxalate or calcium phosphate stones. In the right amounts, calcium can block other substances in the digestive tract that may cause stones. It suggests the best sources may be low-oxalate, plant-based foods such as calcium-fortified juices, cereals and breads, some vegetables and some types of beans.

Food is the key word. The Cleveland Clinic notes that taking large amounts of calcium supplements can sometimes cause an issue, and it suggests meeting your calcium needs through food unless your doctor recommends otherwise. Its list of supplements that may raise stone risk also includes vitamin C and turmeric, so review any supplement with your provider before starting it.

Calcium is only one piece. The NIDDK says the first thing to settle is which type of stone you had, because the food changes that help depend on it. Based on the type, you may be able to prevent more stones by adjusting how much sodium, animal protein, calcium or oxalate you eat. A dietitian who specializes in stone prevention can help you plan meals.

Some advice applies broadly. Both sources put fluids first. The NIDDK calls drinking enough liquid, mainly water, the most important thing you can do, and notes that studies have shown the DASH diet can reduce the risk of kidney stones. More sodium raises your chance of stones, and it hides in canned, packaged and fast foods, condiments, seasonings and meats. Animal protein may raise the risk too, so the NIDDK suggests swapping some meat for beans, dried peas and lentils, which are high in protein and low in oxalate.

The Cleveland Clinic adds that citrus fruit such as lemons, limes and oranges contain citrate, which neutralizes acid in urine and helps stop stones from forming. It also reminds readers that diet is not the only factor: stones often run in families, and if you keep getting them despite precautions, your provider may order more testing for personalized recommendations.

Why does fluid matter so much? The Cleveland Clinic explains that low urine volume lets excess vitamins, salts, acids and other waste build up in the kidneys, and waste that lingers is more likely to bond together into a crystal that becomes a future stone. Water is best, the clinic says, but almost anything you pour into a cup, including coffee and tea, helps keep you hydrated. The NIDDK says to talk with a health care professional about how much liquid you should drink, and it notes the advice is different if you have kidney failure.

Sweets deserve a look too. The Cleveland Clinic says a high sugar intake through sweets and treats can raise the calcium concentration in urine and lower citrate, which fuels stone growth. One of its urologists explains that uric acid stones form in an acidic environment, so citrus that makes urine less acidic may help with that type as well. The NIDDK adds that studies have shown being overweight increases your risk of kidney stones, and a dietitian can help you plan meals. If stones keep coming back, the Cleveland Clinic notes your provider may also prescribe medications to help prevent them.

This does not mean you should start calcium supplements, and no single diet fits every stone type. Talk with your doctor about which stone you had before you change what you eat.