Editing Ulcerative colitis (section)

===Environmental factors===
Many hypotheses have been raised for environmental factors contributing to the pathogenesis of ulcerative colitis, including [[Diet (nutrition)|diet]], [[breastfeeding]] and medications. Breastfeeding may have a protective effect in the development of ulcerative colitis.<ref name=Xu_Breastfeeding_UC>{{cite journal | vauthors = Xu L, Lochhead P, Ko Y, Claggett B, Leong RW, Ananthakrishnan AN | title = Systematic review with meta-analysis: breastfeeding and the risk of Crohn's disease and ulcerative colitis | journal = Alimentary Pharmacology & Therapeutics | volume = 46 | issue = 9 | pages = 780–789 | date = November 2017 | pmid = 28892171 | pmc = 5688338 | doi = 10.1111/apt.14291 }}</ref><ref>{{cite journal | vauthors = Corrao G, Tragnone A, Caprilli R, Trallori G, Papi C, Andreoli A, Di Paolo M, Riegler G, Rigo GP, Ferraù O, Mansi C, Ingrosso M, Valpiani D | title = Risk of inflammatory bowel disease attributable to smoking, oral contraception and breastfeeding in Italy: a nationwide case-control study. Cooperative Investigators of the Italian Group for the Study of the Colon and the Rectum (GISC) | journal = International Journal of Epidemiology | volume = 27 | issue = 3 | pages = 397–404 | date = June 1998 | pmid = 9698126 | doi = 10.1093/ije/27.3.397 | doi-access = free }}</ref> One study of [[isotretinoin]] found a small increase in the rate of UC.<ref>{{cite journal | vauthors = Wolverton SE, Harper JC | title = Important controversies associated with isotretinoin therapy for acne | journal = American Journal of Clinical Dermatology | volume = 14 | issue = 2 | pages = 71–76 | date = April 2013 | pmid = 23559397 | doi = 10.1007/s40257-013-0014-z | s2cid = 918753 }}</ref>

As the colon is exposed to many dietary substances which may encourage [[inflammation]], dietary factors have been hypothesized to play a role in the [[pathogenesis]] of both ulcerative colitis and Crohn's disease. However, research does not show a link between diet and the development of ulcerative colitis. Few studies have investigated such an association; one study showed no [[Association (statistics)|association]] of refined [[sugar]] on the number of people affected of ulcerative colitis.<ref>{{cite journal | vauthors = Järnerot G, Järnmark I, Nilsson K | title = Consumption of refined sugar by patients with Crohn's disease, ulcerative colitis, or irritable bowel syndrome | journal = Scandinavian Journal of Gastroenterology | volume = 18 | issue = 8 | pages = 999–1002 | date = November 1983 | pmid = 6673083 | doi = 10.3109/00365528309181832 }}</ref> High intake of [[unsaturated fat]] and [[vitamin B6]] may enhance the risk of developing ulcerative colitis.<ref name="Geerling 2000">{{cite journal | vauthors = Geerling BJ, Dagnelie PC, Badart-Smook A, Russel MG, Stockbrügger RW, Brummer RJ | title = Diet as a risk factor for the development of ulcerative colitis | journal = The American Journal of Gastroenterology | volume = 95 | issue = 4 | pages = 1008–1013 | date = April 2000 | doi = 10.1111/j.1572-0241.2000.01942.x | pmid = 10763951 | s2cid = 11295804 }}</ref> Other identified dietary factors that may influence the development and/or relapse of the disease include meat protein and alcoholic beverages.<ref name="Jowett 2004">{{cite journal | vauthors = Jowett SL, Seal CJ, Pearce MS, Phillips E, Gregory W, Barton JR, Welfare MR | title = Influence of dietary factors on the clinical course of ulcerative colitis: a prospective cohort study | journal = Gut | volume = 53 | issue = 10 | pages = 1479–1484 | date = October 2004 | pmid = 15361498 | pmc = 1774231 | doi = 10.1136/gut.2003.024828 }}</ref><ref name="Andersen 2012">{{cite journal | vauthors = Andersen V, Olsen A, Carbonnel F, Tjønneland A, Vogel U | title = Diet and risk of inflammatory bowel disease | journal = Digestive and Liver Disease | volume = 44 | issue = 3 | pages = 185–194 | date = March 2012 | pmid = 22055893 | doi = 10.1016/j.dld.2011.10.001 }}</ref> Specifically, sulfur has been investigated as being involved in the cause of ulcerative colitis, but this is controversial.<ref name="Tilg 2004">{{cite journal | vauthors = Tilg H, Kaser A | title = Diet and relapsing ulcerative colitis: take off the meat? | journal = Gut | volume = 53 | issue = 10 | pages = 1399–1401 | date = October 2004 | pmid = 15361484 | pmc = 1774255 | doi = 10.1136/gut.2003.035287 }}</ref> [[low-sulfur diet|Sulfur restricted diets]] have been investigated in people with UC and animal models of the disease. The theory of sulfur as an etiological factor is related to the [[gut microbiota]] and mucosal sulfide detoxification in addition to the diet.<ref name="Moore 1998">{{cite journal | vauthors = Moore J, Babidge W, Millard S, Roediger W | title = Colonic luminal hydrogen sulfide is not elevated in ulcerative colitis | journal = Digestive Diseases and Sciences | volume = 43 | issue = 1 | pages = 162–165 | date = January 1998 | pmid = 9508519 | doi = 10.1023/A:1018848709769 | s2cid = 20919357 }}</ref><ref name="Jørgensen 2001">{{cite journal | vauthors = Jørgensen J, Mortensen PB | title = Hydrogen sulfide and colonic epithelial metabolism: implications for ulcerative colitis | journal = Digestive Diseases and Sciences | volume = 46 | issue = 8 | pages = 1722–1732 | date = August 2001 | pmid = 11508674 | doi = 10.1023/A:1010661706385 | s2cid = 30373968 }}</ref><ref name="Picton 2007">{{cite journal | vauthors = Picton R, Eggo MC, Langman MJ, Singh S | title = Impaired detoxication of hydrogen sulfide in ulcerative colitis? | journal = Digestive Diseases and Sciences | volume = 52 | issue = 2 | pages = 373–378 | date = February 2007 | pmid = 17216575 | doi = 10.1007/s10620-006-9529-y | s2cid = 22547709 }}</ref>

As a result of [[Perfluorooctanoic acid#Robert Bilott investigation|a class-action lawsuit and community settlement]] with [[DuPont]], three [[Epidemiology|epidemiologists]] conducted studies on the population surrounding a chemical plant that was exposed to PFOA at levels greater than in the general population. The studies concluded that there was an association between [[Perfluorooctanoic acid|PFOA]] exposure and six health outcomes, one of which being ulcerative colitis.<ref>{{cite journal | last1 = Nicole | first1 = W. | title = PFOA and Cancer in a Highly Exposed Community: New Findings from the C8 Science Panel | doi = 10.1289/ehp.121-A340 | journal = Environmental Health Perspectives | volume = 121 | issue = 11–12 | pages = A340 | year = 2013 | pmid = 24284021| pmc = 3855507}}</ref>