Can Green Tea Cause Kidney Stones?

Kidney stones, hard deposits of minerals and acid salts that form inside the kidneys, can be very painful. Several things can cause kidney stones, including over-concentration of the urine, metabolic or genetic disorders, and infections. Gastric bypass surgery can also increase your chances of developing this condition, because it affects the way your body absorbs calcium — and most kidney stones are calcium-based. Green tea is not a cause of kidney stones, according to MayoClinic.com. In fact, it's quite the opposite — this popular herbal tea is often recommended to help prevent them.

Kidney Stones

Kidney stones form when the urine becomes concentrated, which allows minerals in the urine to crystallize and stick together. Some stones can form from combinations of calcium and oxalate or phosphate — this is the most common type of stone. Infections can cause struvite stones. Uric acid stones can form in the urine of people who are dehydrated, those who eat a high protein diet, or those who have gout. Cystine stones, which are much less common, form in the urine of people who have a hereditary disorder that makes the kidneys excrete excessive amounts of certain amino acids.

Risk Factors

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Risk factors for kidney stones are numerous. A family history of stones and dehydration are two major risk factors. Adult males and obese individuals have an increased risk of developing this condition. Digestive diseases and surgery, such as gastric bypass, that cause changes in the digestive process also put you at higher risk for kidney stones, because they affect your ability to absorb calcium and therefore increase the odds of stones forming substances in your urine. Renal disease and hyperparathyroidism can also increase the risk of kidney stones.

Treating Kidney Stones

Small kidney stones, perhaps the size of a pencil lead or a grain of sand, will sometimes pass if the patient drinks large amounts of water and takes over-the-counter pain medicine, such as ibuprofen. Medical professionals can administer a sound-wave system called lithotripsy that breaks the stones into small fragments, allowing them to pass out of the body in the urine. However, in some cases, surgery is the only option to treat a kidney stone. Although green tea is not used as a treatment, it is recommended to help prevent stones from developing in the first place.

Research on Green Tea

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Although more research is needed, much research shows that green tea can help ward off kidney stones before they occur. According to a November 13, 2009 article in PhysOrg.com, green tea contains compounds called "phenols" that make it more difficult for large kidney stones to form by changing the shape of the mineral crystals so they cannot clump together 2. A study in the May 2006 "Journal of Endourology" reported that epigallocatechin gallate, one of the main polyphenols in green tea, inhibited urinary stone formation in rats through its antioxidant effects 34. In the January 2005 edition of “Journal of Urology,” researchers reported that green tea decreased calcium oxalate stone formation in rats, alleging that this correlation was likely due to the antioxidants in the tea 3.

Considerations and Warnings

Although the Mayo Clinic claims that green tea is safe for adult use in moderation. However, it's important to keep in mind that both the tea and green tea extract contain caffeine, which can cause problems such as restlessness, anxiety and insomnia in some people. If you have questions or concerns about green tea or kidney stones, consult a health care professional.