Efficient removal of oxalate from tea by pre-infusion.

Purpose: Most kidney stones are made of calcium oxalate. Many kidney stone formers stop drinking tea, resulting in reduced diuresis. The oxalate in tea diffuses rapidly during infusion. We hypothesized that pre-infusion of tea could significantly reduce its oxalate content.

Methods: Tea bags were infused for 0.5, 1, 2 or 3 minutes, with or without a pre-infusion of 10, 30 or 60 seconds (16 conditions, n=4/condition). Oxalate concentration was measured and a blind organoleptic analysis was carried out by 4 operators.

Results: A 10 seconds pre-infusion reduced the oxalate concentration of tea by 10 to 33% (p<0.05). A 30 seconds pre-infusion reduced it by 38 to 51% (p<0.05) and a 1 minute pre-infusion by 59 to 65% (p<0.05). Pre-infusion had no significant impact on satisfaction scores for taste, smell or visual appearance.

Conclusion: Pre-infusion of tea significantly reduces oxalate intake (by up to 2/3 depending on conditions).