The old man recalled afterwards that he usually likes to eat tofu. Tofu contains a lot of calcium, and the gypsum of tofu also contains calcium, which eventually leads to kidney calculi.
▲? Kidney calculi in the news [1]
Is that so?
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Kidney calculi is clinically called urolithiasis, which is the most common urinary system disease. Calcium oxalate stone is the most common stone, followed by phosphate stone and sodium oxalate stone. Its principle is similar to the salt precipitation learned in middle school: the proportion of some minerals in urine increases, which leads to the increase of urine concentration and the formation of crystals.
The exact cause of urinary calculi is not clear, which may be caused by many factors. But the risk factors in kidney calculi are relatively clear.
The first is metabolic abnormality, for example, the substances that inhibit the formation and aggregation of crystals in urine are reduced, and the inhibition is less, and the output will naturally increase; Followed by local causes, such as infection, organ malformation, stenosis and so on. , hinder the flow of urine, there will be the possibility of crystallization; Some drugs may also lead to an increase in urine concentration and cause stones.
Of course, our focus is on dietary factors.
In 2000, scholars from Sichuan University surveyed 7,625 residents in Baoan District, Shenzhen. Understand the local people's eating habits by issuing questionnaires; At the same time, a laboratory doctor was hired to carry out B-ultrasound examination on volunteers.
The results showed that there was a significant positive correlation between high protein diet and urolithiasis, but there was no significant correlation between high fat diet and urolithiasis. A high calcium diet helps to reduce the incidence of urolithiasis. [2]
Take the most common calcium oxalate stone as an example. As the name implies, it is a crystal formed by oxalate and calcium.
Excessive intake of protein from food will produce transient and endogenous acid products in the body. These products will enter the urine, which will promote the increase of urinary calcium, thus increasing the risk of urinary calculi.
Regarding calcium, it was previously thought that limiting calcium in diet could reduce the absorption of calcium, thus reducing the content of calcium in urine and reducing the production of calcium oxalate. [3]
However, recent research shows that under normal circumstances, the ratio of calcium to oxalic acid in urine is 5: 1. When the ratio of calcium to oxalic acid is close to 1: 1, calcium oxalate stones are most likely to appear. Low-calcium diet can promote the absorption of oxalate, leading to an increase in the proportion of oxalate in urine, thus promoting the formation of urinary calculi. On the contrary, calcium can combine with oxalic acid in the intestine to form insoluble substances, which cannot be dissolved and absorbed. Therefore, high calcium diet can inhibit the absorption of oxalic acid, thus reducing the risk of urinary calculi. [4]
Tofu is a kind of food with average protein content and extremely high calcium content. According to the food composition table of China, 100g north tofu (made with brine) contains 9.2g of protein, and 100g south tofu (made with gypsum) contains 5.7g of protein, which is far less than meat. At the same time, 100g north tofu (made with brine) contains 105mg calcium, and 100g south tofu (made with gypsum) contains 1 13mg calcium, which is similar to hot milk. [5]
As for the gypsum used for tofu, its main component is calcium sulfate. Calcium sulfate is extremely insoluble in water, even if a little remains, it will not be absorbed when eaten in the stomach.
Therefore, eating more tofu will not increase the risk of urolithiasis. Not only will it not increase, calcium supplementation through diet, just like drinking more water, is a good way to prevent urolithiasis.
Truth: Tofu contains high calcium. Eating more tofu will not only increase the risk of urinary calculi, but also help prevent urinary calculi.
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refer to
155-year-old uncle took out 420 stones because he loves tofu _ News _ Tencent [EB/OL]. [20 17-03-06]. The signed articles published on this website only represent the author's views and have nothing to do with this website. If there is any infringement, you are responsible.
Author: Zhao Yanchang