You may have heard that drinking tea can lead to kidney stones. In most cases, this is true. But there's one tea that may actually prevent kidney stones.
The reason most teas cause kidney stones is because they have a high oxalate content. Oxalate is the conjugate base of oxalic acid, which is the cause of the most common type of kidney stone. About 80% of kidney stones form when oxalate combines with calcium to form crystalline masses in the urine. Normally, your urine contains a substance that will break down the stones. So most kidney stones just pass without a major event. But when that doesn't happen, the pain can be excruciating. It can even lead to swollen kidneys, blood in the urine, nausea, vomiting, and fever.
While most teas contribute to stone formation, green tea doesn't. That's because green tea binds to calcium oxalate. When it does, it creates flat crystals that break down easily. The more green tea you drink, the flatter the stones become.
A research team from Sichuan University in Chengdu, China recently discovered this unusual characteristic of green tea. They made the discovery by growing calcium oxalate crystals and then exposing the crystals to various conditions and substances. Green tea was one of the substances that had the best results: "Our results suggest that drinking green tea might be a good habit for the prevention of human stone formation," says head researcher Xudong Li.
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These results confirmed other studies that showed similar beneficial action from green tea. However, these studies couldn't explain why the tea worked. One such study, from a 1998 issue of the Annals of Internal Medicine, followed 81,093 women between the ages of 40 and 86 years with no history of kidney stones. The researchers in this study found that for each cup of green tea consumed every day, the subjects reduced their risk of kidney stones by 8%.
Another study found that men could drop their risk of kidney stones by 14% with each cup of tea they drank. What's amazing about these studies is that the researchers measured the level of calcium oxalate in the participants' urine and found that it went up. So the green tea does increase calcium oxalate levels. But because of its binding action, it prevents the calcium oxalate from forming into sharp, painful crystals.
What's more, green tea has much less oxalate in it than black tea. Green tea has approximately .23 to 1.15 mgs per gram, while black tea has between 4.6 and 5.1 mgs per gram. So even without its binding action, the green tea would be less likely to cause as many painful stones as black tea.
In addition, green tea is great for you in other ways, which I've told you about in past issues of Nutrient Insider. Its catechin content makes it extremely good for you. So feel free to drink green tea every day. It could save you from the pain of kidney stones.
If you don't like green tea, brew it with a flavored tea and add a little Stevia. It makes the bitter taste much easier to tolerate. And if you just don't want to drink green tea, you can try Green Tea Extract. We don't have any studies on this supplement and kidney stones, but it will give you all of the other health benefits of green tea. And it's possible it could help you avoid kidney stones.
Your insider for better health,
Steve Kroening is the editor of Nutrient Insider, a twice-a-week email newsletter that brings you the latest healing breakthroughs from the world of nutrition and dietary supplements. For over 20 years, Steve has worked hand-in-hand with some of the nation's top doctors, including Drs. Robert Rowen, Frank Shallenberger, Nan Fuchs, William Campbell Douglass, and best-selling author James Balch. Steve is the author of the book Practical Guide to Home Remedies. As a health journalist, Steve's articles have appeared in countless magazines, blogs, and websites.