Matcha, a finely ground powder of specially grown and processed green tea leaves, has gained immense popularity for its concentrated nutrient profile and vibrant flavor. Consumers often seek out this beverage for its reputation as a health-promoting drink, rich in antioxidants and amino acids.
However, questions have arisen regarding potential adverse effects from naturally occurring compounds found in plant-based foods. A common concern for those at risk of urological issues is whether regular consumption of this powdered tea contributes to the formation of kidney stones, centering on the presence of oxalates.
The Role of Oxalates in Kidney Stone Formation
The vast majority of kidney stones, approximately 70% to 80%, are composed of calcium oxalate. Oxalates are naturally occurring compounds, produced by the body and absorbed from the diet, which are normally excreted through the kidneys.
The process of stone formation begins when the concentration of oxalate and calcium ions in the urine becomes too high, leading to supersaturation. Once urine is supersaturated, the calcium and oxalate ions bind together to form microscopic calcium oxalate crystals. These crystals will typically be flushed out, but in susceptible individuals, they can adhere to the lining of the renal tubules, growing and aggregating into a painful kidney stone. Oxalate is a strong chemical promoter of stone formation, estimated to be 15 to 20 times more potent than calcium itself in driving this crystallization process.
Measuring Oxalate Content in Matcha
Determining the actual risk from matcha requires looking at its specific oxalate content compared to other dietary sources. Because matcha is a whole leaf powder consumed entirely, its oxalate load per serving can be higher than steeped tea. A typical two-gram serving of matcha powder, often used for a standard cup, may contain around 12.6 milligrams of oxalate.
Some studies indicate that high-grade matcha, which undergoes a shading process during cultivation, may contain even higher levels. Compared to other high-oxalate foods, this level is modest; for example, a 100-gram serving of raw spinach contains nearly 1,000 milligrams of oxalate. Ultimately, the risk is less about the mere presence of oxalates and more about the total amount consumed daily, especially when compared to other major sources in the diet.
Practical Steps to Reduce Risk While Consuming Matcha
Individuals who are prone to forming calcium oxalate kidney stones can continue to enjoy matcha by adopting specific dietary strategies that mitigate the risk.
Increase Fluid Intake
One effective preventative measure is to increase fluid intake, as this dilutes the concentration of stone-forming minerals in the urine. Consuming enough water to achieve a daily urine output of approximately 2.5 liters helps to flush out any crystals before they can aggregate into stones.
Pair Matcha with Calcium
Another highly actionable strategy involves pairing matcha with a source of dietary calcium. When calcium is consumed at the same time as oxalate, the two compounds bind together in the gastrointestinal tract. This binding prevents the oxalate from being absorbed into the bloodstream and reaching the kidneys, allowing the calcium-oxalate compound to be excreted in the feces. Pairing a matcha latte with dairy milk or a calcium-fortified plant-based alternative is a simple way to implement this protective measure. Moderation in the overall diet is also important, ensuring matcha consumption does not significantly contribute to an excessive daily oxalate intake.