Diet taboos for urinary stones

The core dietary taboos for patients with urinary stones are never the one-size-fits-all list of "cannot eat tofu, cannot drink milk, and cannot touch spinach" posted on the Internet. Instead, they should first clarify the specific taboos of their own stone components, and at the same time avoid common dietary behaviors that increase the risk of stone formation. This is the conclusion that I want to tell you first after spending 6 years in the Department of Urology and contacting thousands of urinary stone patients.

I just received a 28-year-old Internet operator last week. He just had extracorporeal lithotripsy last month. He came to me for a follow-up consultation with the "list of foods to avoid for urinary stones" found in a certain red book. He said that he had stopped eating all calcium-containing foods this month. He dared not touch milk, and even looked at tofu. As a result, he has been having cramps recently, and his blood calcium was almost a quarter lower than the normal value. I asked him if he had done an analysis of the components of the stones. He looked confused and said that he had never heard of such a test. He only knew that others said that calcium should not be used when growing stones.

Don’t think this is an exception. I have met more than half of the stone patients whose understanding of taboos is based on the unified template uploaded online. They are not aware that the taboos for stones with different components are not the same thing at all. Some even say the exact opposite.

Take the most common calcium oxalate stone as an example. In the past, the older generation always said that if you have stones, you cannot supplement calcium or drink high-calcium milk. Now this view has long been controversial. The latest version of the "China Urolithiasis Diagnosis and Treatment Guidelines" clearly states that a daily normal dietary calcium intake of 800-1000mg will combine with free oxalic acid in the intestines, reducing the amount of oxalic acid absorbed into the blood and eventually into the urine, which can actually reduce the risk of recurrence of calcium oxalate stones. What you really need to avoid is casually taking large doses of calcium supplements, as well as the habit of eating high-oxalate foods and large amounts of calcium at the same time - for example, if you eat a pound of unblanched spinach with two large cups of high-calcium milk, it is indeed prone to problems, but if you normally drink a glass of milk and eat a piece of tofu, there is no need to panic. Of course, there are also those who insist that "calcium is the culprit of calcium oxalate stones". After all, some patients do have abnormal calcium metabolism, and excessive calcium intake will increase urinary calcium levels. Therefore, the safest way is to first analyze the components of the stones, and then adjust them based on their own urinary calcium and urinary oxalate indicators, so as not to exclude all calcium-containing foods.

If you have uric acid stones, the focus of your taboo is not calcium, but high-purine foods. However, there is also a common misunderstanding here. Many people say that patients with uric acid stones cannot eat soy products at all. In fact, many studies have shown that processed tofu and soy milk have lost most of their purine content. They are low-purine foods. Normal consumption will not increase uric acid at all. Instead, animal offal, thick broth, seafood + beer combinations are the ones that should be touched as little as possible. Of course, if your uric acid is controlled very well and is stable below 300 μmol/L, it’s not a big deal if you occasionally crave for two steamed prawns. Just drink two more glasses of water and urinate twice more after eating. You don’t have to put such a heavy dietary burden on yourself.

There are also relatively rare infectious stones (magnesium ammonium phosphate stones). The taboos are different from the first two. Patients with this type should try to avoid foods that can alkalize urine, such as soda and a lot of citrus fruits. Instead, they can eat more acidic foods to acidify urine and reduce the growth of stones.

Having said that, no matter what type of stones you have, there are two common minefields that you really need to avoid. This is also the consensus of all urological surgeons, and there is no controversy.

The first is to drink too little water, or always use sweet drinks, milk tea, or strong coffee instead of plain water. The most exaggerated patient I have ever seen was a salesman who drank 4 cups of iced milk tea a day while running his business in the summer and almost never touched plain water. His urine concentration was as high as concentrated orange juice. He developed two 0.7cm stones in half a year. When he started to feel pain, he rolled on the floor of the clinic. To put it bluntly, drinking water is the most cost-effective way to prevent stones. If you drink more than 2000ml of plain water every day, your urine will be as pale as one or two steeps of light tea, which can flush out most of the stone-forming substances. It is more effective than memorizing a list of ten taboos.

The second is a long-term diet high in salt and sugar. Eating too much salt will increase the calcium content in the urine, and eating too much sugar will affect the metabolism of uric acid, both of which provide fuel to stones in disguise. Just like the cured meats, candied fruits, and takeaway heavy-flavored dishes that many people love to eat, it is okay to eat them once in a while. If you eat them every day, even if you avoid all taboo foods, stones will still come to your doorstep easily.

Some patients have asked me before whether drinking lemonade can cause fossilization. There is really no conclusion yet on this. One group believes that the citric acid in lemonade can combine with calcium ions in urine and reduce the formation of calcium oxalate crystals. The other group believes that the citric acid content of the lemonade that ordinary people drink every day cannot reach the effective concentration at all. On the contrary, drinking too much can easily hurt the stomach. I generally recommend that patients drink it appropriately if they don’t have stomach problems, but don’t rely on this to cure their illnesses. If you really have stones, you should see a doctor first.

In fact, the dietary taboos for urinary stones are really not as mysterious as those posted on the Internet, and you don’t need to dare to eat this or that. The core is to first understand the ingredients of your own stones, and don’t use other people’s lists to apply to yourself. If you have passed stones before, or had them removed through surgery, taking it to the hospital for a component analysis that costs tens of dollars will be more reliable than searching blindly for a week. Of course, there is no need to be too anxious. I have seen many patients who have adjusted their eating and drinking habits without recurrence of stones for more than ten years. To put it bluntly, this is a lifestyle disease. Just adjust slowly.