Editing Vitamin A (section)

===Cancer===
Meta-analyses of intervention and observational trials for various types of cancer report mixed results. Supplementation with β-carotene did not appear to decrease the risk of cancer overall, nor specific cancers including: pancreatic, colorectal, prostate, breast, melanoma, or skin cancer generally.<ref name=Druesne2010>{{cite journal | vauthors = Druesne-Pecollo N, Latino-Martel P, Norat T, Barrandon E, Bertrais S, Galan P, Hercberg S | title = Beta-carotene supplementation and cancer risk: a systematic review and metaanalysis of randomized controlled trials | journal = International Journal of Cancer | volume = 127 | issue = 1 | pages = 172–84 | date = July 2010 | pmid = 19876916 | doi = 10.1002/ijc.25008 | s2cid = 24850769 | doi-access = free | title-link = doi }}</ref> High-dose β-carotene supplementation unexpectedly resulted in a higher incidence of lung cancer and of total mortality in people who were cigarette smokers.<ref name=PKIN2020Carotenoids/>

For dietary retinol, no effects were observed for high dietary intake and [[breast cancer]] survival,<ref>{{cite journal | vauthors = He J, Gu Y, Zhang S | title = Vitamin A and Breast Cancer Survival: A Systematic Review and Meta-analysis | journal = Clinical Breast Cancer | volume = 18 | issue = 6 | pages = e1389–e400 | date = December 2018 | pmid = 30190194 | doi = 10.1016/j.clbc.2018.07.025 | s2cid = 52169953 }}</ref> risk of [[liver cancer]],<ref>{{cite journal | vauthors = Leelakanok N, D'Cunha RR, Sutamtewagul G, Schweizer ML | title = A systematic review and meta-analysis of the association between vitamin A intake, serum vitamin A, and risk of liver cancer | journal = Nutrition and Health | volume = 24 | issue = 2 | pages = 121–31 | date = June 2018 | pmid = 29792083 | doi = 10.1177/0260106018777170 | s2cid = 43944154 }}</ref> risk of [[bladder cancer]]<ref>{{cite journal | vauthors = Tang JE, Wang RJ, Zhong H, Yu B, Chen Y | title = Vitamin A and risk of bladder cancer: a meta-analysis of epidemiological studies | journal = World Journal of Surgical Oncology | volume = 12 | issue = | pages = 130 | date = April 2014 | pmid = 24773914 | pmc = 4030017 | doi = 10.1186/1477-7819-12-130 | doi-access = free | title-link = doi }}</ref> or risk of [[colorectal cancer]],<ref>{{cite journal | vauthors = Liu Y, Yu Q, Zhu Z, Zhang J, Chen M, Tang P, Li K | title = Vitamin and multiple-vitamin supplement intake and incidence of colorectal cancer: a meta-analysis of cohort studies | journal = Medical Oncology | volume = 32 | issue = 1 | pages = 434 | date = January 2015 | pmid = 25491145 | doi = 10.1007/s12032-014-0434-5 | s2cid = 25904916 }}</ref><ref name="Xu2013">{{cite journal | vauthors = Xu X, Yu E, Liu L, Zhang W, Wei X, Gao X, Song N, Fu C | title = Dietary intake of vitamins A, C, and E and the risk of colorectal adenoma: a meta-analysis of observational studies | journal = European Journal of Cancer Prevention | volume = 22 | issue = 6 | pages = 529–39 | date = November 2013 | pmid = 24064545 | doi = 10.1097/CEJ.0b013e328364f1eb | s2cid = 36958552 }}</ref> although the last review did report lower risk for higher β-carotene consumption.<ref name="Xu2013"/> In contrast, an inverse association was reported between retinol intake and relative risk of [[esophageal cancer]],<ref>{{cite journal | vauthors = Li K, Zhang B | title = The association of dietary β-carotene and vitamin A intake on the risk of esophageal cancer: a meta-analysis | journal = Revista Espanola de Enfermedades Digestivas | volume = 112 | issue = 8 | pages = 620–26 | date = August 2020 | pmid = 32543872 | doi = 10.17235/reed.2020.6699/2019 | s2cid = 219724574 | doi-access = free | title-link = doi }}</ref> [[gastric cancer]],<ref>{{cite journal | vauthors = Wu Y, Ye Y, Shi Y, Li P, Xu J, Chen K, Xu E, Yang J | title = Association between vitamin A, retinol intake and blood retinol level and gastric cancer risk: A meta-analysis | journal = Clinical Nutrition | volume = 34 | issue = 4 | pages = 620–26 | date = August 2015 | pmid = 25008141 | doi = 10.1016/j.clnu.2014.06.007 }}</ref> [[ovarian cancer]],<ref>{{cite journal | vauthors = Wang Q, He C | title = Dietary vitamin A intake and the risk of ovarian cancer: a meta-analysis | journal = Bioscience Reports | volume = 40 | issue = 4 | date = April 2020 | pmid = 32149329 | pmc = 7138903 | doi = 10.1042/BSR20193979 }}</ref> [[pancreatic cancer]],<ref>{{cite journal | vauthors = Zhang T, Chen H, Qin S, Wang M, Wang X, Zhang X, Liu F, Zhang S | title = The association between dietary vitamin A intake and pancreatic cancer risk: a meta-analysis of 11 studies | journal = Bioscience Reports | volume = 36 | issue = 6 | date = December 2016 | pmid = 27756825 | pmc = 5293573 | doi = 10.1042/BSR20160341 }}</ref> [[lung cancer]],<ref name="Yu2015">{{cite journal | vauthors = Yu N, Su X, Wang Z, Dai B, Kang J | title = Association of Dietary Vitamin A and β-Carotene Intake with the Risk of Lung Cancer: A Meta-Analysis of 19 Publications | journal = Nutrients | volume = 7 | issue = 11 | pages = 9309–24 | date = November 2015 | pmid = 26569298 | pmc = 4663591 | doi = 10.3390/nu7115463 | doi-access = free | title-link = doi }}</ref> [[melanoma]],<ref>{{cite journal | vauthors = Zhang YP, Chu RX, Liu H | title = Vitamin A intake and risk of melanoma: a meta-analysis | journal = PLOS ONE | volume = 9 | issue = 7 | pages = e102527 | date = 2014 | pmid = 25048246 | pmc = 4105469 | doi = 10.1371/journal.pone.0102527 | doi-access = free | title-link = doi | bibcode = 2014PLoSO...9j2527Z }}</ref> and [[cervical cancer]].<ref>{{cite journal | vauthors = Zhang X, Dai B, Zhang B, Wang Z | title = Vitamin A and risk of cervical cancer: a meta-analysis | journal = Gynecologic Oncology | volume = 124 | issue = 2 | pages = 366–73 | date = February 2012 | pmid = 22005522 | doi = 10.1016/j.ygyno.2011.10.012 }}</ref> For lung cancer, an inverse association was also seen for β-carotene intake, separate from the retinol results.<ref name="Yu2015"/> When high dietary intake was compared to low dietary intake, the decreases in relative risk were in the range of 15 to 20%. For gastric cancer, a meta-analysis of prevention trials reported a 29% decrease in relative risk from retinol supplementation at 1500 μg/day<ref name="Kong2014">{{cite journal | vauthors = Kong P, Cai Q, Geng Q, Wang J, Lan Y, Zhan Y, Xu D | title = Vitamin intake reduce the risk of gastric cancer: meta-analysis and systematic review of randomized and observational studies | journal = PLOS ONE | volume = 9 | issue = 12 | pages = e116060 | date = 2014 | pmid = 25549091 | pmc = 4280145 | doi = 10.1371/journal.pone.0116060 | doi-access = free | title-link = doi | bibcode = 2014PLoSO...9k6060K }}</ref>