Tea must be drunk hot! Recently, researchers at Loyola University Medical Center in Chicago, USA, stated that drinking cold tea can lead to kidney stones.
A professor of urology at Loyola University Chicago explained that when tea cools, it contains a large amount of oxalate, which can form small stones, block the ureter, and increase the risk of developing kidney stones. In response, Professor Gao Lin, an expert in urology from the Fourth Affiliated Hospital of Harbin Medical University, explained that about 80% of urinary tract stones are calcium oxalate crystals, and patients with kidney stones should drink less tea and more water.
For the average person, digestive juices can buffer the formation of stones, so the chance of developing stones from drinking cold tea is much lower. However, since tea is rich in oxalic acid, to be on the safe side, special attention should be paid to the amount and way of drinking tea:
1. When tea cools, it contains a large amount of oxalate, which can form small stones. Furthermore, steeping tea in warm water does not extract the beneficial chemical components as thoroughly as with hot water. Therefore, it is best to first brew the tea with water at 70°C-80°C and drink it when the temperature drops to around 60°C. Do not exceed 70°C, as tea that is too hot can cause strong irritation to the throat, esophagus, and stomach, leading to mucosal lesions. In addition, repeated steeping or steeping for too long will cause oxidation and denaturation of tea polyphenols, vitamins, and proteins in the tea, and the number of harmful microorganisms will also increase.
2. Some people are used to reheating cold tea with more hot water to continue drinking it. If no additional tea leaves are added during this process, the oxalate content in the tea will not change, so there is no need to worry. However, adding hot water midway does not easily dissolve the nutrients in the tea, nor does it bring out the flavor easily.
3. Do not drink tea on an empty stomach, as this will lead to more oxalic acid being absorbed into the body, increasing the likelihood of stone formation. This is especially true for patients with kidney stones, who can drink water or lemonade to quench their thirst, as lemon contains a large amount of sodium citrate, which can prevent kidney stones.
4. It is not advisable to drink too much tea every day. Generally, for a healthy adult, drinking 6-10 grams of tea per day, brewed in 2-3 separate infusions, is sufficient. For people with heavy physical labor, high energy consumption, a diet high in greasy foods, or high consumption of tobacco and alcohol, especially those in high-temperature environments or with frequent exposure to toxic substances, it is okay to drink a little more each day.