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Oxalic acid is a naturally occurring component of tea, chocolate, beer, soybeans, wheat germ, some fruits and vegetables, and is especially high in spinach and other dark leaf greens. Oxalic acid is usually excreted in urine as a harmless by-product of digestion and assimilation, however it can also combine with minerals, and particularly with calcium, to form oxalates.

These oxalates are salt crystals that can be irritating to human tissue and can contribute to the formation of kidney and bladder stones. This is especially a concern for those who have kidney or bladder problems or those with an inability to properly absorb fat.

Of all the tea types, black and black decaffeinated teas contain the most oxalic acid, typically ranging from 12 to 30 mg per cup. Green, green decaffeinated and white teas typically contain 6 to 18 mg oxalic acid per cup.  However test results tend to vary cup-to-cup and some of our independent laboratory testing of oxalic acid content has resulted in quantities too small to be measured or to contain none at all.

Herbal teas typically contain only 0 to 2 mg oxalic acid per cup.

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