Editing Selenium (section)

===Deficiency===
{{Main|Selenium deficiency}}
Selenium deficiency can occur in patients with severely compromised [[intestine|intestinal]] function, those undergoing [[total parenteral nutrition]], and<ref>{{cite journal |title= Effect of micronutrient status on natural killer cell immune function in healthy free-living subjects aged ≥90 y |volume= 71 |issue= 2 |pages= 590–598 |journal= American Journal of Clinical Nutrition |pmid= 10648276 |date=2000 |last1= Ravaglia |first1=G.|last2= Forti |first2=P. |last3= Maioli |first3=F. |last4= Bastagli |first4=L. |last5= Facchini |first5=A. |last6= Mariani |first6=E. |last7= Savarino |first7=L. |last8= Sassi |first8=S. |last9= Cucinotta |first9=D. |last10=Lenaz |first10=G. |display-authors=3|doi= 10.1093/ajcn/71.2.590 |doi-access= free }}</ref> in those of advanced age (over 90). Also, people dependent on food grown from selenium-deficient soil are at risk. Although [[New Zealand]] soil has low levels of selenium, the residents have not detected adverse health effects.<ref>{{cite web| url= http://www.medsafe.govt.nz/Profs/PUarticles/Sel.htm |website= Prescriber Update Articles |title= Selenium |access-date= 2009-07-13 |publisher= New Zealand Medicines and Medical Devices Safety Authority |author= MedSafe Editorial Team}}</ref>

Selenium deficiency, defined by low (<60% of normal) selenoenzyme activity levels in brain and endocrine tissues, occurs only when a low selenium level is linked with additional stress, such as high exposures to [[Mercury (element)|mercury]]<ref>{{cite journal|last1=Ralston |first1=N. V. C.|last2=Raymond |first2=L. J.|title=Dietary selenium's protective effects against methylmercury toxicity|journal=Toxicology|date=2010|volume=278|pages=112–123|doi=10.1016/j.tox.2010.06.004|pmid=20561558|issue=1|bibcode=2010Toxgy.278..112R }}</ref> or increased oxidant stress from vitamin E deficiency.<ref>{{cite book| title =Essentials of Human Nutrition |edition= 2nd |publisher= Oxford University Press |date= 2002 |isbn= 978-0-19-262756-8 |first1= Jim |last1= Mann |first2= A. Stewart |last2= Truswell}}</ref>

Selenium interacts with other nutrients, such as [[iodine]] and [[vitamin E]]. The effect of selenium deficiency on health remains uncertain, particularly concerning [[Kashin–Beck disease]].<ref>{{cite journal |title= Selenium and iodine supplementation of rural Tibetan children affected by Kashin-Beck osteoarthropathy |first1=R. |last1= Moreno-Reyes |first2=F. |last2= Mathieu |first3=M. |last3= Boelaert |first4=F. |last4= Begaux |first5=C. |last5= Suetens |first6=M. T. |last6= Rivera |first7=J. |last7= Nève |first8=N. |last8= Perlmutter |first9=J. |last9= Vanderpas |journal= American Journal of Clinical Nutrition |volume= 78 |issue= 1 |pages= 137–144 |date= 2003 |pmid= 12816783 |display-authors= 3|doi= 10.1093/ajcn/78.1.137 |doi-access= free }}</ref> Also, selenium interacts with other minerals, such as [[zinc]] and [[copper]]. High doses of selenium supplements in pregnant animals might disturb the zinc:copper ratio and lead to zinc reduction; in such treatment cases, zinc levels should be monitored. Further studies are needed to confirm these interactions.<ref>{{cite journal|title= The effect of dietary organic and inorganic selenium supplementation on serum Se, Cu, Fe and Zn status during the late pregnancy in Merghoz goats and their kids|first1=R.|last1 =Kachuee |first2=M. |last2= Moeini |first3=M. |last3= Suori |volume= 110 |issue= 1 |pages= 20–27 |journal= Small Ruminant Research |date=2013 |doi=10.1016/j.smallrumres.2012.08.010}}</ref>

In the regions (e.g., regions within North America) where low selenium soil levels lead to low concentrations in the plants, some animal species may be deficient unless selenium is supplemented with diet or injection.<ref>National Research Council, Subcommittee on Sheep Nutrition (1985). ''Nutrient requirements of sheep''. 6th ed., National Academy Press, Washington, {{ISBN|0309035961}}.</ref> [[Ruminant]]s are particularly susceptible. In general, absorption of dietary selenium is lower in ruminants than in other animals and is lower in forages than in grain.<ref name="NRCsr2007">National Research Council, Committee on Nutrient Requirements of Small Ruminants (2007). ''Nutrient requirements of small ruminants''. National Academies Press, Washington, {{ISBN|0-309-10213-8}}.</ref> Ruminants grazing certain forages, e.g., some [[white clover]] varieties containing [[cyanogenic glycoside]]s, may have higher selenium requirements,<ref name="NRCsr2007" /> presumably because cyanide is released from the [[aglycone]] by [[glucosidase]] activity in the rumen<ref>{{cite journal|last1=Coop |first1=I. E.|last2=Blakely |first2=R. L. |date=1949|title= The metabolism and toxicity of cyanides and cyanogenic glycosides in sheep|journal= New Zealand Journal of Science and Technology|volume= 30|pages= 277–291}}</ref> and glutathione peroxidases are deactivated by the cyanide acting on the glutathione [[Moiety (chemistry)|moiety]].<ref>{{cite journal|last1=Kraus |first1=R. J.|last2=Prohaska |first2=J. R.|last3=Ganther |first3=H. E. |date=1980|title= Oxidized forms of ovine erythrocyte glutathione peroxidase. Cyanide inhibition of 4-glutathione:4-selenoenzyme|journal= Biochimica et Biophysica Acta (BBA) - Enzymology |pmid=7426660|volume=615|pages= 19–26|doi=10.1016/0005-2744(80)90004-2|issue=1}}</ref> Neonate ruminants at risk of [[Nutritional muscular dystrophy|white muscle disease]] may be administered both selenium and vitamin E by injection; some of the WMD [[Myopathy|myopathies]] respond only to selenium, some only to vitamin E, and some to either.<ref>Kahn, C. M. (ed.) (2005). ''Merck Veterinary Manual''. 9th ed. Merck & Co., Inc., Whitehouse Station, {{ISBN|0911910506}}.</ref>

==== Nutritional sources of selenium ====
Dietary selenium comes from meat, nuts, cereals, and mushrooms. [[Brazil nut]]s are the richest dietary source (though this is soil-dependent since the Brazil nut does not require high levels of the element for its own needs).<ref>{{cite journal |last1=Barclay |first1=Margaret N. I. |last2=MacPherson |first2=Allan |last3=Dixon |first3=James |date=1995 |title=Selenium content of a range of UK food |journal=Journal of Food Composition and Analysis |volume=8 |issue=4 |pages=307–318 |doi=10.1006/jfca.1995.1025}}</ref><ref>{{cite web |title=Selenium Fact Sheet |url=http://ods.od.nih.gov/factsheets/selenium.asp#h2 |publisher=The Office of Dietary Supplements, [[National Institutes of Health]] |place=United States}} Includes a list of selenium-rich foods.</ref>

The US [[Recommended Dietary Allowance]] (RDA) of selenium for teenagers and adults is 55&nbsp;[[Microgram|μg]]/day. Selenium as a dietary supplement is available in many forms, including multi-vitamins/mineral supplements, which typically contain 55 or 70&nbsp;μg/serving. Selenium-specific supplements typically contain either 100 or 200&nbsp;μg/serving.{{Citation needed|date=June 2024}} In June 2015, the US [[Food and Drug Administration]] (FDA) published its final rule establishing a requirement for minimum and maximum levels of selenium in [[infant formula]].<ref>{{Cite web |title=FDA Issues Final Rule to Add Selenium to List of Required Nutrients for Infant Formula |url=https://www.fda.gov/Food/NewsEvents/ConstituentUpdates/ucm451982.htm |url-status=dead |archive-url=https://wayback.archive-it.org/7993/20171114120142/https://www.fda.gov/Food/NewsEvents/ConstituentUpdates/ucm451982.htm |archive-date=November 14, 2017 |access-date=2015-09-10 |publisher=Food and Drug Administration |df=mdy-all}}</ref>