Recently, it was reported that "a 60-year-old man in Taiwan Province Province used tea instead of water for a long time, but found a 0.7-0.8 cm stone in the ureter. It is said that he had stones when he was less than 30 years old and relapsed 30 years later. " It was followed by a series of rumors, such as "drinking tea is easy to get kidney calculi" and "drinking tea for a long time may increase the risk of kidney calculi".
Deny/refute/spread rumors
A large-scale population survey has proved that drinking tea will not increase the incidence of kidney calculi, and may also reduce the risk of stones.
The logic of "drinking tea is easy to get kidney calculi" is that tea is rich in oxalic acid, which can form calcium oxalate with calcium in human body, while kidney calculi is mostly calcium oxalate stones, so drinking tea is easy to get kidney calculi. However, there are many loopholes.
The formation of kidney calculi is very complicated, and its mechanism is not completely clear. At present, from the biochemical point of view, it is considered that the main mechanism of stone formation is in three aspects: 1. The stone-forming substances in urine are supersaturated; 2. Decrease of stone inhibiting substances and increase of promoting substances; 3. Renal tubular epithelial cells are damaged, and urinary epithelial cells are mainly damaged by renal tubular cells, which play an important role in the whole process of stone formation.
As the first factor, diet is also considered to be an important reason for the formation of kidney calculi, including eating spinach, which has accumulated a lot of oxalic acid in the body; Eating animal liver and seafood leads to abnormal purine metabolism, excessive fat intake, high sugar content and excessive protein. There are also many factors leading to the latter two, such as obesity, hyperglycemia, dyslipidemia, genetic abnormalities and so on. Studies have shown that abnormal distribution of phospholipids in cell membrane is easy to induce calcium oxalate stones, and this kind of population is mainly obese with high triglyceride and cholesterol, which is consistent with the frequent population in kidney calculi.
Is the amount of oxalic acid reaching the kidneys due to drinking tea really high? Although the formation of kidney calculi is related to the large intake and abnormal accumulation of oxalic acid, the content of oxalic acid in different kinds of tea with different production processes is not the same. The oxalic acid content of green tea and oolong tea is lower than that of black tea, so it is suspected that "tea is rich in oxalic acid".
In fact, the content of oxalic acid in many foods is much higher than that in tea. The Guide to Diagnosis and Treatment of Urological Diseases in China clearly points out that spinach is the most taboo for kidney calculi patients, and there are also foods with high oxalic acid content such as cabbage, chocolate, peanuts and beets. However, most oxalic acid has been combined with other ingredients in food (such as calcium) and excreted through feces before it is absorbed and reaches the kidneys. As one of many factors that human body ingests oxalic acid, only a small amount of tea leaves is ingested after soaking in water, which is not enough to cause the formation of kidney calculi.
Some experiments have proved that the risk of kidney calculi formed by oxalic acid content in tea is very low through a large-scale population survey. The incidence of kidney calculi among these people who have the habit of drinking tea has not increased, but it can be slightly reduced. Many studies have confirmed the benefits of tea to the kidneys. For example, tea polyphenols in tea can protect proximal renal tubular epithelial cells from injury induced by oxalic acid and calcium oxalate crystals. Tea polyphenols can effectively increase the activity of intracellular antioxidant enzymes, inhibit lipid peroxidation, scavenge oxygen free radicals and reduce the damage of renal tubular epithelial cells, thus reducing the incidence of stones; Tea polysaccharide in tea can obviously improve the biochemical indexes in the pathogenesis of diabetic nephropathy in mice; EGCG in tea can inhibit the formation of calcium oxalate kidney calculi in kidney, and has obvious protective effect on renal function. EGCG can reduce the damage of peroxide to the body, reduce the risk of stone formation and so on.
However, this does not mean that everyone can drink tea freely. Incorrect drinking tea will still increase the risk of stones. If you drink a lot of tea for a long time without washing it, or drink strong tea for a long time, tannic acid, theobromine and other ingredients in strong tea will promote the formation of stones. So how to drink tea correctly? Drink moderate and light tea, wash the tea before drinking, and wash away about 80% oxalic acid in the tea. It is suggested that the daily consumption of tea is about 5 ~ 12g, and 3 ~ 4 times of brewing is appropriate.
In a word, people who drink tea occasionally don't have to worry about kidney calculi, while those who are used to drinking tea every day, if they are healthy and have normal metabolism, have little chance of suffering from kidney calculi. The theory that drinking tea leads to kidney calculi is unscientific.
Rumor-dispelling expert: Wu Yibo, Master of Pharmacy Management and Clinical Pharmacy, Peking University Pharmaceutical University, and head of the Youth Group of the Medical Professional Committee of the Chinese Popular Science Writers Association.
Evaluation expert: Dong Xiaoqiu, chief physician, postgraduate tutor and third-level professor of the Fourth Affiliated Hospital of Harbin Medical University.
Producer: Cop China-Scientific Refutation