Editing Kwashiorkor (section)

=== Low protein intake ===
[[File:Protein-energy malnutrition world map - DALY - WHO2002.svg|thumb|upright=1.2|[[Disability-adjusted life year]]s per 100,000&nbsp;inhabitants for protein-energy malnutrition in 2002:<ref>{{cite web |url=https://www.who.int/entity/healthinfo/statistics/bodgbddeathdalyestimates.xls |title=Mortality and Burden of Disease Estimates for WHO Member States in 2002 |format=xls |work=World Health Organization |year=2002 |access-date=5 October 2020 |archive-date=16 January 2013 |archive-url=https://web.archive.org/web/20130116174540/http://www.who.int/healthinfo/statistics/bodgbddeathdalyestimates.xls |url-status=live }}</ref>{{Div col|small=yes|colwidth=10em}}
{{legend|#b3b3b3|no data}}
{{legend|#ffff65|fewer than 10}}
{{legend|#fff200|10–100}}
{{legend|#ffdc00|100–200}}
{{legend|#ffc600|200–300}}
{{legend|#ffb000|300–400}}
{{legend|#ff9a00|400–500}}
{{legend|#ff8400|500–600}}
{{legend|#ff6e00|600–700}}
{{legend|#ff5800|700–800}}
{{legend|#ff4200|800–1000}}
{{legend|#ff2c00|1000–1350}}
{{legend|#cb0000|more than 1350}}
{{div col end}}]]
Kwashiorkor is a severe form of [[malnutrition]] associated with a low-protein diet.<ref name="Benjamin & Lappin Kwashiorkor"/> The extreme lack of protein causes an osmotic imbalance in the [[Human gastrointestinal tract|gastrointestinal system]] causing swelling of the gut diagnosed as an [[edema]] or retention of water.<ref name="williams1935" />

Extreme fluid retention observed in individuals suffering from kwashiorkor is accompanied by irregularities in the [[lymphatic system]] as well as disruptions of capillary exchange. The lymphatic system serves three major purposes: fluid recovery, immunity, and [[lipid]] absorption. Victims of kwashiorkor commonly exhibit reduced ability to recover fluids, immune system failure, and low lipid absorption. Fluid recovery by the lymphatic system is accomplished by the re-vascularization of fluid and macromolecules from the interstitial space, allowing these constituents of whole blood to be returned to the venous circulation. Compromised fluid recovery may contribute to the phenomenon of extravascular fluid accumulation in kwashiorkor.<ref>{{cite journal | year = 1950 | title =  Nova et Vetera| journal = The British Medical Journal | volume = 2 | issue = 4673| page = 284 | doi = 10.1136/bmj.2.4673.267 | s2cid = 220181068}}</ref>

The low protein theory for the pathogenesis of kwashiorkor has been used to teach that capillary exchange between the lymphatic system and circulating blood is impaired by a reduced oncotic (i.e. colloid osmotic pressure, COP) in the blood, as a consequence of inadequate protein intake, so that the hydrostatic pressure gradient, which favors extravasation of fluid from small vessels, is not overcome. Proteins, mainly albumin, are responsible for creating the COP observed in the blood and tissue fluids. The difference in the COP of the blood and tissue tends to favor the reentry of fluid from the extravascular space, into the circulatory system. This tendency is opposed by the venous hydrostatic pressure, which tends to favor the exit of fluid from small vessels, into the interstitial space. The low protein theory for the pathogenesis of kwashiorkor held that a deficiency of serum proteins, caused by inadequate protein intake, disrupted this balance, and thus impaired the return flow of fluid from the interstitium into the capillary and venous structures. It has been taught that this is what accounts for the accumulation of extravascular fluid in kwashiorkor, and the subsequent pedal edema and abdominal distension.<ref>{{cite book |last=Saladin |first=Kenneth | name-list-style = vanc |title=Anatomy and Physiology |edition=6th |location=New York |publisher=McGraw Hill |year=2012 |pages=766–767, 809–811 |isbn=978-0-07-337825-1 }}</ref>

The low protein theory, which relies heavily upon Starling's theory for the movement of fluid in biological systems, provided a compelling rationale for the pathogenesis of edema in kwashiorkor. What it does not explain, however, is the entire array of disturbances that define the kwashiorkor syndrome. These include irritability, anorexia, skin desquamation, skin depigmentation, hair discoloration, reduced mitochondrial respiration, impaired lipid export from the liver without an accompanying reduction of lipoprotein synthesis, 'oxidative stress', glutathione depletions, [[transsulfuration]] disturbances, diffuse DNA hypomethylation, immune dysfunction, decreased transmethylation activity, and sulfated [[glycosaminoglycan]] deficiencies. It is now generally acknowledged that by itself, the low protein theory does not adequately account for the pathogenesis of kwashiorkor. More complex deficiencies are at work. These have still not been established. <ref>{{cite journal|vauthors=Tierney EP, Sage RJ, Shwayder T|date=2010|title=Kwashiorkor from a severe dietary restriction in an 8-month infant in suburban Detroit, Michigan: case report and review of the literature|journal=International Journal of Dermatology|volume=49|issue=5|pages=500–6|doi=10.1111/j.1365-4632.2010.04253.x|pmid=20534082|s2cid=13050691}}</ref>

Social factors are also relevant. Ignorance of nutrition can be a cause. A case was described where parents who fed their child [[cassava]] failed to recognize malnutrition because of the edema caused by the syndrome and believed the child was well-nourished despite the development of kwashiorkor.<ref>{{cite web|title=Malnutrition in Third World Countries|url=http://www.religion-online.org/showarticle.asp?title=1405.|website=www.religion-online.org|access-date=2 March 2017|archive-url=https://web.archive.org/web/20150919024954/http://www.religion-online.org/showarticle.asp?title=1405.|archive-date=19 September 2015|url-status=dead}}</ref>