title: Do teas rich in antioxidants reduce the physicochemical and peroxidative risk factors for calcium oxalate nephrolithiasis in humans? Pilot studies with Rooibos herbal tea and Japanese green tea.
abstract: Several experimental and animal studies have demonstrated that substances rich in antioxidants can reduce the physicochemical and peroxidative risk factors for calcium oxalate (CaOx) renal stone formation in urine and blood. However, there are very few such investigations in humans. In the present pilot study, two varieties of tea, a green one from Japan (JGT) and a herbal one from South Africa (Rooibos) (RT), both rich in antioxidants, were administered to a group of CaOx stone formers (SF) (n = 8) for 30 days. Both teas were analysed for polyphenols by high-performance liquid chromatography and for minerals by plasma atomic and optical emission spectroscopy. 24 h urines (baseline and day 30) were analysed for lithogenic factors. CaOx metastable limits and crystal nucleation and growth kinetics were also determined in each urine sample. Deposited crystals were inspected by scanning electron microscopy. Blood samples were collected (baseline and day 30). Biomarkers of oxidative stress including plasma and urinary thiobarbituric acid reactive substances (TBARS) and urinary N-acetyl-β-D-glucosaminidase (NAG) were also determined. Urinary physicochemical risk factors were also investigated after ingestion of RT for 30 days in two control groups (CG1 and CG2), the latter one of which consisted of habitual JGT drinkers. Statistical analyses were performed using Wilcoxon signed rank tests and Mann-Whitney tests for paired and independent measurements, respectively. Several flavonoids and catechins were quantified in RT and JGT, respectively, confirming that both teas are rich sources of antioxidants. Mineral content was found to be far below dietary reference intakes. There were no significant changes in any of the urinary physicochemical or peroxidative risk factors in the control groups or in SF, except for the supersaturation (SS) of brushite (Bru) which decreased in the latter group after ingestion of JGT. Crystal morphology showed a tendency to change from mixed CaOx mono- and di-hydrate to monohydrate after ingestion of each tea. Since the latter form has a stronger binding affinity for epithelial cells, this effect is not protective. Analysis of the physicochemical and peroxidative risk factors in CG1 and CG2 did not reveal any evidence of a synergistic effect between the two teas. Paradoxically, baseline risk factors in the habitual JGT control group were significantly raised relative to those in CG1. Our preliminary results suggest that ingestion of RT and JGT does not reduce the risk factors for CaOx stone formation in humans, but these findings need to be tested in further studies involving much larger sample sizes.
authors.affiliation: Department of Chemistry, University of Cape Town, Rondebosch, 7700, South Africa. allen.rodgers@uct.ac.za.
authors.forename: A
authors.initials: A
authors.lastname: Rodgers
authors.affiliation: Department of Chemistry, University of Cape Town, Rondebosch, 7700, South Africa.
authors.forename: M
authors.initials: M
authors.lastname: Mokoena
authors.affiliation: Department of Statistical Sciences, University of Cape Town, Rondebosch, South Africa.
authors.forename: I
authors.initials: I
authors.lastname: Durbach
authors.affiliation: Division of Urology, University of Cape Town, Rondebosch, South Africa.
authors.forename: J
authors.initials: J
authors.lastname: Lazarus
authors.affiliation: Division of Urology, University of Cape Town, Rondebosch, South Africa.
authors.forename: S
authors.initials: S
authors.lastname: de Jager
authors.affiliation: Department of Urology, University of Stellenbosch, Stellenbosch, South Africa.
authors.forename: H
authors.initials: H
authors.lastname: Ackermann
authors.affiliation: Durbanville Mediclinic, Durbanville, South Africa.
authors.forename: I
authors.initials: I
authors.lastname: Breytenbach
authors.affiliation: Department of Nephro-urology, Nagoya City University, Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Okada
authors.affiliation: Department of Nephro-urology, Nagoya City University, Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Usami
authors.affiliation: Department of Nephro-urology, Nagoya City University, Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Hirose
authors.affiliation: Department of Nephro-urology, Nagoya City University, Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: R
authors.initials: R
authors.lastname: Ando
authors.affiliation: Department of Nephro-urology, Nagoya City University, Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Yasui
authors.affiliation: Department of Nephro-urology, Nagoya City University, Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Kohri
mesh_terms: D000293:Adolescent; D000328:Adult; D000975:Antioxidants / Q000032:analysis* / Q000627:therapeutic use*; D055598:Chemical Phenomena; D006801:Humans; D008297:Male; D053040:Nephrolithiasis / Q000453:epidemiology* / Q000517:prevention & control*; D010084:Oxidation-Reduction; D010865:Pilot Projects; D012307:Risk Factors; D013662:Tea / Q000737:chemistry*; D000069459:Teas, Herbal / Q000032:analysis*; D055815:Young Adult
chemical_list: D000975:Antioxidants; D013662:Tea; D000069459:Teas, Herbal
keywords: Antioxidants; Calcium oxalate; Crystallization risk factors; Green tea; Nephrolithiasis; Peroxidative risk factors; Rooibos tea