title: The production of p-cresol sulfate and indoxyl sulfate in vegetarians versus omnivores.
abstract: OBJECTIVE
  The uremic solutes p-cresol sulfate (PCS) and indoxyl sulfate (IS) are generated by colon bacteria acting on food components that escape absorption in the small bowel. The production of these potentially toxic compounds may thus be influenced by diet. This study examined whether production of PCS and IS is different in vegetarians and omnivores.
  
  
  METHODS
  The production of PCS and IS was assessed by measuring their urinary excretion rates in participants with normal kidney function. Studies were carried out in 15 vegetarians and 11 individuals consuming an unrestricted diet. Participants recorded food intake over 4 days and collected urine over the final 2 days of each of two study periods, which were 1 month apart.
  
  
  RESULTS
  Average PCS excretion was 62% lower (95% confidence interval [95% CI], 15-83) and average IS excretion was 58% lower (95% CI, 39-71) in vegetarians than in participants consuming an unrestricted diet. Food records revealed that lower excretion of PCS and IS in vegetarians was associated with a 69% higher (95% CI, 20-139) fiber intake and a 25% lower (95% CI, 3-42) protein intake. PCS and IS excretion rates varied widely among individual participants and were not closely correlated with each other but tended to remain stable in individual participants over 1 month.
  
  
  CONCLUSIONS
  PCS and IS production rates are markedly lower in vegetarians than in individuals consuming an unrestricted diet.
authors.affiliation: Department of Medicine, Palo Alto VA Health Care System, Stanford University, Palo Alto, California, USA.
authors.forename: Kajal P
authors.initials: KP
authors.lastname: Patel
authors.forename: Frank J-G
authors.initials: FJ
authors.lastname: Luo
authors.forename: Natalie S
authors.initials: NS
authors.lastname: Plummer
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Hostetter
authors.forename: Timothy W
authors.initials: TW
authors.lastname: Meyer
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000652:urine; D002140:California; D003408:Cresols / Q000652:urine*; D015930:Diet Records; D014676:Diet, Vegetarian; D004063:Digestion; D005260:Female; D006801:Humans; D007200:Indican / Q000652:urine*; D007668:Kidney / Q000378:metabolism / Q000502:physiology; D008297:Male; D008460:Meat; D008875:Middle Aged; D013463:Sulfuric Acid Esters / Q000652:urine*; D013997:Time Factors
chemical_list: D015415:Biomarkers; D003408:Cresols; D013463:Sulfuric Acid Esters; C408690:4-cresol sulfate; D007200:Indican