Abstract:
Previous studies have disclosed that black tea contains between 1.5 - 6.5 mg of soluble
oxalates/g tea and thus regular consumption of black tea will lead to a moderate intake of
soluble oxalate each day (Savage et al., 2003). Therefore, consumption of black tea may
increase the urinary oxalate concentration, possibly leading to an increased risk of kidney
oxalate stone formation (Brinkley et al., 1990). On the contrary, it is claimed that its
consumption reduces the risk of kidney stones formation and in fact leads to a reduced
risk of kidney stone formation by 14% in males (Curhan et al., 1996) and 8% in females
(Curhan et al., 1998). Human kidney stones are predominantly made of calcium oxalate
(more than 75%) (Savage et al., 2003). Three main mechanisms have been suggested for
dissolving oxalate based kidney stones (Savage et al., 2003): an increased urinary flushing
leading to high oxalate excretion; an increased level of calcium consumption via food and
beverages leading to reduced oxalate absorption in the digestive tract; and by dissolving of
calcium oxalate present in the kidney stones by chemical constituents ingested in to the
body.
The aim of this study was to examine the ability of black tea infusion (BTI) to dissolve
kidney stones, since BTI has been shown to reduce urinary oxalate levels (Savage et al.,
2003). The study was conducted in vitro on human kidney stones collected following
surgery using low grown BOPF grade Sri Lankan orthodox black tea infusion.
