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Herbal tea: An alternative to regular tea for those who form calcium oxalate stones

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Of every 10,000 hospital admissions, 7 to 21 are attributed to renal stone disease, and close to 80% of kidney stones are composed primarily of calcium oxalate (1). Hyperoxaluria is a known risk factor for formation of calcium oxalate stones and for recurrence (2). The observation that urinary oxalate concentrations correlate with episodes of kidney stone formation led to our hypothesis that decreasing urinary oxalate concentration will decrease risk of formation of calcium oxalate stones (2). Thus, the elimination of certain foods and beverages that are high in oxalate from the diets of those who form calcium oxalate stones may prevent recurrences.

Regular black tea is known to have a high oxalate concentration, and its consumption without added milk has been shown to increase urinary oxalate concentrations (3,4). These findings have prompted some researchers to recommend the elimination of black tea from the diets of those who form oxalate stones (5). Herbal teas often contain ingredients that are known to contain oxalate; examples include citrus peels, berries, and leaves.

The objective of our study was to measure the oxalate concentration of herbal teas to determine whether herbal teas would be acceptable as alternative hot beverages for people who tend to form calcium oxalate stones.

METHODS

Manufacturers of internationally available brands of herbal tea were contacted to determine the varieties of herbal teas that were most popular with North American consumers. Fourteen different herbal teas were identified. Two widely available popular brands of regular black tea, one brand of green tea, and one brand of coffee were included for comparison. AU teas were purchased locally as packaged by their manufacturers.

Boiling tap water (250 mL) was added to each of the samples. All teas were steeped for 5 minutes without stirring; the tea bag was then removed. Samples of regular black tea...