Matcha, a finely ground powder of specially grown green tea leaves, has gained popularity worldwide. As its consumption increases due to perceived health benefits, questions arise regarding its potential health impacts. A common concern is whether regular matcha intake contributes to kidney stone formation. This article explores the connection between matcha and kidney stones, examining the underlying science.
Understanding Kidney Stones
Kidney stones are solid masses that form in the kidneys when certain urine substances become highly concentrated and crystallize. They vary in size, from a grain of sand to a golf ball. While small stones may pass unnoticed, larger ones can cause significant pain and block urine flow, leading to complications.
The most common type is the calcium oxalate stone, accounting for approximately 80% of cases. These stones form when calcium and oxalate, a natural compound, bind together in the urine. Other types include uric acid, struvite, and cystine stones, each forming under different conditions. Factors like dehydration, diet, obesity, and certain medical conditions can increase susceptibility to kidney stone formation.
Matcha’s Oxalate Connection
Oxalates are naturally occurring compounds found in many plants, including teas. When consumed, oxalates bind with calcium in the digestive tract, typically forming an insoluble compound that is eliminated from the body. If absorbed into the bloodstream, they travel to the kidneys and can combine with calcium in the urine, potentially forming calcium oxalate crystals. These crystals can then aggregate and grow into kidney stones, particularly if the urine is highly concentrated or lacks substances that inhibit crystal formation.
Matcha, like other green teas, contains oxalates. The concentration of oxalates in matcha can vary based on growing conditions, processing methods, and variety. While specific oxalate content can fluctuate, some sources indicate matcha may contain around 12.6 milligrams of oxalate per 2-gram serving. This level is generally considered moderate compared to foods known for their very high oxalate content, such as spinach, rhubarb, beets, or nuts.
Matcha contributes to overall dietary oxalate intake, not as a sole source. The formation of kidney stones from dietary oxalates usually occurs in susceptible individuals with high urine oxalate levels (hyperoxaluria) or other predisposing factors. For most people, consuming oxalate-containing foods as part of a balanced diet does not lead to kidney stone formation. The interaction between dietary oxalate, calcium, and other urinary components determines the risk.
Strategies to Reduce Risk
For individuals concerned about kidney stones, several strategies can help reduce risk. Maintaining adequate hydration is essential, as drinking sufficient fluids helps dilute waste products in the urine, making crystal formation less likely. Healthcare providers often recommend drinking more than 10 to 12 glasses of fluid daily to achieve pale yellow urine.
Consuming calcium-rich foods alongside oxalate-rich foods is beneficial. When calcium and oxalate are present together in the digestive tract, they bind before oxalate is absorbed into the bloodstream, reducing the amount that reaches the kidneys. Aiming for two to three servings of dairy or other calcium-rich foods daily, such as milk or yogurt, supports this process. It is generally advised to obtain calcium from food sources rather than supplements, as supplements might increase stone risk in some cases.
Practicing moderation in matcha consumption, along with other high-oxalate foods, is advisable. While matcha’s oxalate content is not exceptionally high, a varied and balanced diet limiting excessive intake of any single food group is recommended. Reducing intake of animal protein, sodium, and refined sugars can also contribute to a lower risk of stone formation. Individuals with a history of kidney stones or concerns about their risk should consult a healthcare professional or registered dietitian for personalized dietary advice.