Diet taboos for stones

There are no foods that are 100% absolutely forbidden to eat. The "cannot eat spinach, cannot drink milk, and cannot touch soy products" posted on the Internet are all one-sided conclusions. The real dietary taboos should be determined based on your stone composition and daily metabolic level. The core principle is to "prioritize quantity control, reduce excessive intake of oxalic acid/purine, and ensure adequate drinking water." Blind taboos may increase the risk of stone recurrence.

I met a 30-year-old programmer during my rotation in the Department of Urology. He was so painful that he curled up on a stretcher and was sent in. It was found that calcium oxalate stones blocked the ureter. He said that after he was diagnosed with small stones six months ago, he stopped eating everything that was told on the Internet. He did not touch milk or spinach, and drank white porridge with pickles every day. However, the result was that the stones had grown by 2mm, and he was still deficient in calcium and felt dizzy when he stood up after squatting for a long time. To put it bluntly, it is stepping on the trap of "one size fits all". Nowadays, many taboos on the Internet are based on the views of the old guide, which have been updated a long time ago.

Speaking of this, someone must ask, is the previous statement about not eating high oxalate foods a lie? Of course not, it depends on what kind of stone you have. Calcium oxalate stones account for 70% to 80% of all urinary tract stones. It is indeed necessary to pay attention to the intake of high oxalate foods, but it is not completely prohibited. In the early years, academic circles did advocate the complete avoidance of high-oxalate foods such as spinach, amaranth, and strong tea. However, clinical data in recent years show that the stone recurrence rate of patients who completely avoid these foods is not lower than that of those who eat in controlled quantities. On the contrary, many people have developed new stones due to insufficient dietary fiber intake and reduced intestinal oxalic acid conjugates. I have an old patient who did not dare to touch any spinach before. Later, he heard from me that he should blanch spinach in boiling water for 1 minute before eating it - it can remove about 60% of the oxalic acid. Then eat it with a mouthful of milk or tofu. The oxalic acid combines with calcium in the intestines to form unabsorbed calcium oxalate and is excreted. After eating it two or three times a week, no new stones were found during a year's review.

Contrary to what many people think, patients with calcium oxalate stones do not need to deliberately eat less calcium. The old view in the early years was to limit calcium intake. Now domestic and foreign urinary guidelines have changed: Calcium in the normal diet (800~1000mg per day, which is about the amount of 300ml of milk and a piece of tofu the size of a palm) will not increase the risk of stones, but can reduce the absorption of oxalic acid in the intestine. On the contrary, what should be avoided is to avoid taking large-dose supplements that contain more than 500mg of calcium in a single tablet, which can easily cause short-term spikes in urinary calcium concentration and increase the risk of stones.

Let’s talk about uric acid stones, which account for the second highest proportion. The taboos for this are relatively clear, but high purine is not completely untouchable. Many people black out seafood and animal offal after being diagnosed with uric acid stones. In fact, it is not necessary. As long as the daily purine intake is controlled within 200mg, it is perfectly fine to eat 100g of boiled shrimp and two bites of pork liver to satisfy the craving every week. What we really need to be wary of is excessive intake in a short period of time: last time I met a young man who ate crayfish with iced Coke after get off work every day for a week. The pain caused him to go to the emergency room in the middle of the night. The uric acid soared to 620 μmol/L, and he had three small uric acid stones in his kidneys. I would like to mention sweet drinks here, especially ice cola and fruit tea that contain a lot of fructose. No matter what kind of stones you have, you should avoid touching them. Fructose will promote the production of uric acid and increase the concentration of urinary oxalic acid. The risk is higher than eating two mouthfuls of seafood. Previously, a 16-year-old child drank cola as water for half a year and was also diagnosed with stones.

There is another topic that has been controversial for many years: can soy products be eaten? The old saying is that soybeans are high in purine and oxalic acid, and stone patients should not eat them. In fact, it has been verified that the purine of dry soybeans is indeed not low, but after being made into tofu and soy milk, most of the purine and oxalic acid are diluted and removed by water. The purine of 100g of tofu is less than 70mg, which is completely a low-purine food. The oxalic acid content is much lower than spinach. As long as you don't eat half a piece of tofu in one meal, there will be no problem at all. I myself am a high-risk group for calcium oxalate stones. I drink a cup of soy milk every morning and have not found any stones during my two-year physical examination and B-ultrasound.

Many people focus on what to eat, but ignore the issue of drinking which is more important than eating. No matter what kind of stone it is, it is the most basic requirement to drink more than 2000ml of warm boiled water every day. Do not use milk tea, soft drinks, or strong tea as a substitute. I have seen too many patients holding a thermos cup to make strong tea every day, and they think they have drunk enough water. As a result, the oxalic acid content in strong tea is high. If you drink it on an empty stomach, it will be absorbed more, which will make you more likely to develop stones. If you really want to drink tea, drink it lighter. Drinking it after a meal is basically no problem.

To put it bluntly, the dietary taboos for stones are never a blacklist for you to follow. It is more like a reminder for healthy eating: don’t be heavy-mouthed, don’t be greedy, and drink enough water. It’s better than anything else. If you really want to eat two bites of hot pot or eat some spinach, the sky will not fall down. The best way is to save a sample for stone composition analysis when the stone is passed out for the first time or when the stone is removed during surgery. It is more useful than searching 10 taboo posts on the Internet. After that, you can review the B-ultrasound every six months, and basically there will be no major problems.