Editing Bracken (section)

==Toxicity==
Bracken contains the [[carcinogen]]ic compound [[ptaquiloside]], which causes damage to DNA, thus leading to cancers of the digestive tract.<ref>{{cite journal |doi=10.1093/toxsci/kfr329 |pmid=22143989 |title=Pteridium aquilinum and Its Ptaquiloside Toxin Induce DNA Damage Response in Gastric Epithelial Cells, a Link with Gastric Carcinogenesis |journal=Toxicological Sciences |volume=126 |issue=1 |pages=60–71 |year=2012 |last1=Gomes |first1=Joana |last2=Magalhães |first2=Ana |last3=Michel |first3=Valérie |last4=Amado |first4=Inês F |last5=Aranha |first5=Paulo |last6=Ovesen |first6=Rikke G |last7=Hansen |first7=Hans C B |last8=Gärtner |first8=Fátima |last9=Reis |first9=Celso A |last10=Touati |first10=Eliette |doi-access=free }}</ref> High [[stomach cancer]] rates are found in [[Japan]] and [[North Wales]], where bracken is often eaten, but it is unclear whether bracken plays a role.<ref>{{cite journal|author1=I A Evans |author2=B Widdop |author3=R S Jones |author4=G D Barber |author5=H Leach |author6=D L Jones |author7=R Mainwaring-Burton |name-list-style=amp | title=The possible human hazard of the naturally occurring bracken carcinogen|journal=Biochem. J.|year=1971|volume= 124 |issue=2 |pages=29P–30P|pmid=5158492|pmc=1177200 |doi=10.1042/bj1240029pa}}</ref> Consumption of ptaquiloside-contaminated milk is thought to contribute to human gastric cancer in the Andean states of [[Venezuela]].<ref>{{cite journal |doi=10.1002/1097-0215(200002)9999:9999<::AID-IJC1028>3.0.CO;2-H |title=Possible association between gastric cancer and bracken fern in Venezuela: An epidemiologic study |journal=International Journal of Cancer |volume=91 |issue=2 |pages=252–259 |year=2001 |last1=Alonso-Amelot |first1=Miguel E |last2=Avendaño |first2=Marisabel |pmid=11146454 |doi-access=free }}</ref> The [[spore]]s have also been implicated as carcinogens.

However, ptaquiloside is water-soluble and destroyed in heat (by cooking) and alkaline conditions (by soaking).<ref>{{cite web|url=http://www.fs.fed.us/database/feis/plants/fern/pteaqu/all.html|title=Pteridium aquilinum|website=www.fs.fed.us|access-date=6 April 2018}}</ref> Korean and Japanese cooks have traditionally soaked the shoots in water and [[ash]] to detoxify the plant before eating.<ref name="pieroni"/> Ptaquiloside also degenerates at room temperature, and denatures almost completely at boiling temperature.<ref name="atlantic">{{cite web|url=https://www.theatlantic.com/health/archive/2011/06/the-bracken-fern-a-natural-born-killer/241271/|title=The Bracken Fern: A Natural Born Killer?|first=Hank|last=Shaw|date=2011-06-30|website=theatlantic.com|access-date=6 April 2018}}</ref> Despite this, moderation of consumption is still recommended to reduce chances of cancer formation.<ref name="atlantic"/> The British Royal Horticultural Society recommends against consumption of bracken altogether, by both humans and livestock.<ref>{{cite web|title=Dol Sot Bibimbap|url=http://apps.rhs.org.uk/advicesearch/Profile.aspx?pid=445|access-date=2011-12-19|archive-url=https://web.archive.org/web/20111111190952/http://apps.rhs.org.uk/advicesearch/profile.aspx?PID=445|archive-date=2011-11-11|url-status=dead}}</ref>

Ptaquiloside has been shown to leach from wild bracken plants into the water supply, which has been implicated in high rates of stomach and oesophageal cancers in areas with high bracken growth, such as Wales and South America.<ref name="rasmussen">{{cite web|url=https://www.theguardian.com/society/2004/sep/09/research.science|title=The fatal fern|first=Kate|last=Ravilious|date=9 September 2004|website=the Guardian|access-date=6 April 2018}}</ref>

Uncooked bracken also contains the [[enzyme]] [[thiaminase]], which breaks down [[thiamine]] (vitamin B1). Excessive consumption of bracken can lead to vitamin B1 deficiency ([[beriberi]]), especially in animals with simple stomachs. [[Ruminant]]s are less vulnerable because they synthesize thiamine.<ref>{{Cite journal |last1=Pan |first1=Xiaohua |last2=Nan |first2=Xuemei |last3=Yang |first3=Liang |last4=Jiang |first4=Linshu |last5=Xiong |first5=Benhai |date=September 2018 |title=Thiamine status, metabolism and application in dairy cows: a review |journal=British Journal of Nutrition |language=en |volume=120 |issue=5 |pages=491–499 |doi=10.1017/S0007114518001666 |issn=0007-1145|doi-access=free |pmid=29986774 }}</ref>

=== In animals ===
Ptaquiloside from bracken has been shown to be [[carcinogen]]ic in some animals.<ref name=Evans71>{{cite journal |vauthors=Evans IA, Widdop B, Jones RS |title=The possible human hazard of the naturally occurring bracken carcinogen |journal=Biochem. J. |volume=124 |issue=2 |pages=29P–30P |date=September 1971 |pmid=5158492 |pmc=1177200 |display-authors=etal|doi=10.1042/bj1240029pa }}</ref> Animals may ingest the plant when other sources of food are unavailable, such as during droughts or after snowfalls.

In cattle, bracken poisoning can occur in acute and chronic forms, acute poisoning being the most common. Milk from cows that have eaten bracken may also contain ptaquiloside, which is especially concentrated in [[buttermilk]].<ref name="rasmussen"/> In pigs and horses, bracken poisoning induces vitamin B1 deficiency.<ref>{{cite book |author1=Auld, RA |author2=Medd, RW |title=Weeds |publisher=Inkata Press |location=Sydney |year=1992 }}</ref>

=== In insects ===
[[Hydrogen cyanide]] is released by the young fronds of bracken when eaten by mammals or insects.<ref>{{cite journal|last=Amelot ME|first=Alonso|date=February 2005|title=Kinetics of the natural evolution of hydrogen cyanide in plants in neotropical Pteridium arachnoideum and its ecological significance|journal=Journal of Chemical Ecology|volume=31 | issue = 2|pages=315–31|doi=10.1007/s10886-005-1343-z|pmid=15856786|bibcode=2005JCEco..31..315A |citeseerx=10.1.1.517.4271|s2cid=30063246}}</ref> Two major insect [[moulting]] hormones, alpha [[ecdysone]] and 20-hydroxyecdysone, are found in bracken. These cause uncontrollable, repeated moulting in insects ingesting the fronds, leading to rapid death.<ref>{{cite journal | title= Insect Hormones: Alpha Ecdysone and 20-Hydroxyecdysone in Bracken Fern|journal= Science|volume=157 |pages=1436–1438|date=22 September 1967 |doi= 10.1126/science.157.3795.1436 |pmid= 6037858 |issue=3795|last1= Kaplanis |first1= J. N. |last2= Thompson |first2= M. J. |last3= Robbins |first3= W. E. |last4= Bryce |first4= B. M. |bibcode= 1967Sci...157.1436K|s2cid= 37746757}}</ref> Bracken is currently under investigation as a possible source of new [[insecticide]]s.<ref>{{cite journal |vauthors=Jbilou R, Amri H, Bouayad N, Ghailani N, Ennabili A, Sayah F |title=Insecticidal effects of extracts of seven plant species on larval development, α-amylase activity and offspring production of ''Tribolium castaneum'' (Herbst) (Insecta: Coleoptera: Tenebrionidae) |journal=Bioresour. Technol. |volume=99 |issue=5 |pages=959–64 |date=March 2008 |pmid=17493805 |doi=10.1016/j.biortech.2007.03.017 |bibcode=2008BiTec..99..959J }}</ref>