TribulusTerrestrisByHYPERLINK"http://altmedicine.about.com/mbiopage.htm"CathyWong,About.comUpdated:September21,2007http://altmedicine.about.com/od/herbsupplementguide/a/tribulus.htmWhatisTribulus?OtherNames:PuncturevineTribulusterrestrisisaherbthathasbeenusedinthetraditionalmedicineofChinaandIndiaforcenturies.Inthemid-1990s,tribulusterrestrisbecameknowninNorthAmericaafterEasternEuropeanOlympicathletessaidthattakingtribulushelpedtheirperformance.Theactivecompoundsintribulusarecalledsteroidalsaponins.Twotypes,calledfurostanolglycosidesandspirostanolglycosides,appeartobeinvolvedwiththeeffectsoftribulus.Thesesaponinsarefoundprimarilyintheleaf.WhyDoPeopleUseTribulus?Tribulusismostoftenusedforinfertility,erectiledysfunction,andlowlibido.Inthelastdecade,ithasbecomepopulartoimprovesportsperformance.TribulushasbeenmarketedtheseconditionsbecauseresearchperformedinBulgariaandRussiaindicatesthattribulusincreaseslevelsofthehormonestestosterone(byincreasingluteinizinghormone),DHEA,andestrogen.Thedesignoftheseresearchstudies,however,hasbeenquestioned.Amorerecentstudyfoundthatfourweeksoftribulussupplements(at10to20milligramsperkgofbodyweightdaily)hadnoeffectonmalesexhormonestestosterone,androstenedione,orluteinizinghormonecomparedtopeoplewhodidnottaketribulus.ErectileDysfunctionPreliminaryanimalstudiesfoundthattribulusheightenedsexualbehaviorandincreasedintracavernouspressure.Thiswasattributedtoincreasesintestosterone.Therehaven'tbeenanywell-designedhumanstudiestoconfirmtheseearlyfindings.BodyCompositionandExercisePerformanceAlthoughtribulushasbecomepopularasasportsperformanceaid,onesmallbutwell-designedstudyfoundithasnoeffectonbodycompositionorexerciseperformance.Fifteensubjectswererandomlyassignedtotribulus(3.21mgperkgbodyweightdaily)oraplacebo.Aftereightweekswithresistancetraining,therewerenochangesinbodyweight,percentagefat,dietaryintake,ormoodineithergroup.Whatwassurprisingwasthatmuscleenduranceactuallyimprovedmoreintheplacebogroup.Muscleendurance(determinedbyth