title: Bioavailability of soluble oxalate from tea and the effect of consuming milk with the tea.
abstract: OBJECTIVE
  To measure the availability of oxalate normally extracted when making tea from two commercially available black teas bought from a supermarket in Christchurch, New Zealand in July 2001.
  
  
  METHODS
  A randomized double crossover study. Six students and four staff consumed six cups of each brand of tea both with and without added milk over a 24 h period. A total urine collection was taken for the initial 6 h followed by a further 18 h. The oxalate content of the urine voided was measured using an enzyme kit method and the availability of the soluble oxalate consumed was measured for the 6 h and the total 24 h sample.
  
  
  METHODS
  University campus.
  
  
  RESULTS
  The mean soluble oxalate content of black tea in the two different commercial tea bags was respectively 6.1 and 6.3 mg soluble oxalate/g tea. The mean availability of the oxalate extracted from tea measured over a 6 h period ranged from 1.9 to 4.7% when tea was consumed without milk. The availability of the soluble oxalate from tea ranged from -3.0 to 2.3% for each of the two brands of tea investigated over a 24 h period.
  
  
  CONCLUSIONS
  These studies show that consuming black tea on a daily basis will lead to a moderate intake of soluble oxalate each day, however the consumption of tea with milk on a regular basis will result in the absorption of very little oxalate from tea.
authors.affiliation: Food Group, AFSD, Lincoln University, Canterbury, New Zealand. savage@lincoln.ac.nz
authors.forename: G P
authors.initials: GP
authors.lastname: Savage
authors.forename: M J S
authors.initials: MJ
authors.lastname: Charrier
authors.forename: L
authors.initials: L
authors.lastname: Vanhanen
mesh_terms: D000328:Adult; D000818:Animals; D001682:Biological Availability; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D007408:Intestinal Absorption; D008297:Male; D008875:Middle Aged; D008892:Milk / Q000737:chemistry; D010070:Oxalates / Q000009:adverse effects / Q000493:pharmacokinetics* / Q000652:urine; D013662:Tea / Q000737:chemistry*
chemical_list: D010070:Oxalates; D013662:Tea