What are the dietary taboos for kidney stones?

The four most important things to avoid when suffering from kidney stones are foods high in oxalic acid, high in purine, high in sodium, and high in added sugar. "You can't drink milk" and "you can't eat tofu" that are widely circulated on the Internet are basically misunderstandings and should not be taken seriously.

I just met a 28-year-old programmer guy a while ago. In order to lose weight, he ate cold spinach and drank sugar-free Coke as water. Six months ago, he had a physical examination and found out about 0.3cm calcium oxalate stones. When he felt the pain, he broke out in a cold sweat. After following the doctor's advice, he reduced the amount of spinach to a maximum of twice a week. He would also blanch the water before eating. He replaced all the cola with warm water. When he was reviewed last month, the stones had been completely discharged.

The first reaction of many people when they are diagnosed with stones is to stop all calcium-containing foods. In fact, there has been an update on this point in the academic world. In the early years, there was indeed a saying that excessive calcium intake would induce stones. However, a large number of studies later confirmed that dietary calcium in a normal diet will combine with oxalic acid in the intestines, which can instead reduce the amount of oxalic acid absorbed by the body and reduce the risk of kidney stones. As long as you do not eat large doses of calcium supplements without permission, drinking a glass of milk and eating a few pieces of tofu every day is completely fine and even recommended. A friend of mine believed what was said on the Internet and gave up all milk and eggs. However, within half a year, he found that his bone density had dropped and his stones were not getting smaller. The gain outweighed the loss.

This does not mean that foods with high oxalic acid cannot be touched at all. Vegetables with high oxalic acid content, such as spinach, amaranth, and bamboo shoots, can be blanched in boiling water for 1 minute in advance to remove more than 70% of the oxalic acid. It is perfectly fine to eat them occasionally, and there is no need to stop eating due to choking.

If you are diagnosed with uric acid stones, you really need to pay more attention to the intake of high-purine foods. I once had an old patient who loved to eat braised stews at least twice a week. His uric acid could not be controlled and the stones recurred three times. Later, he followed the doctor’s advice and stopped all high-purine foods such as stewed stews, animal offal, and rich broth. He drank less beer and ate less seafood. After the uric acid stabilized, he never developed new stones.

What many people tend to overlook is high sodium and high sugar intake. They usually add too much salt in cooking and always eat pickled meats and pickles. Excessive sodium intake will increase the excretion of calcium in the urine, which is equivalent to a higher calcium concentration in the kidneys, which is more likely to combine with oxalic acid to form stones. It is a very practical method to keep a salt-limiting spoon at home and control it within 5g a day. As for high-sugar drinks such as milk tea and carbonated drinks, the fructose in them will promote the production of oxalic acid and uric acid. Even in sugar-free cola, the phosphoric acid additives in it will increase the risk of stones. It is really not as safe as drinking warm boiled water or light lemonade.

By the way, many people on the Internet now say that drinking lemon water can help expel stones. This is still controversial. Only small-scale studies have confirmed that an appropriate amount of citric acid can help prevent calcium oxalate stones. However, if you drink too strong lemon water, you may consume too much acidic substances and increase the burden on your kidneys. Don't blindly believe in folk remedies. If you really have stones, you should first see a doctor to evaluate the size and location.

The composition of stones is different for everyone. If you can take a sample to the hospital for composition analysis when passing stones, subsequent taboos can be more targeted, which is much more reliable than just copying the general taboos on the Internet.