iency ▁include ▁ed ema , ▁failure ▁to ▁th rive ▁in ▁inf ants ▁and ▁children , ▁poor ▁mus cul ature , ▁d ull ▁skin , ▁and ▁thin ▁and ▁frag ile ▁hair . ▁Bio chem ical ▁changes ▁reflect ing ▁protein ▁def ic iency ▁include ▁low ▁ser um ▁album in ▁and ▁low ▁ser um ▁transfer rin . ▁ ▁The ▁am ino ▁ac ids ▁that ▁are ▁essential ▁in ▁the ▁human ▁di et ▁were ▁established ▁in ▁a ▁series ▁of ▁experiments ▁led ▁by ▁William ▁C um ming ▁Rose . ▁The ▁experiments ▁involved ▁element al ▁di ets ▁to ▁health y ▁male ▁gradu ate ▁students . ▁These ▁di ets ▁consisted ▁of ▁corn st arch , ▁suc rose , ▁but ter f at ▁without ▁protein , ▁corn ▁oil , ▁in organ ic ▁sal ts , ▁the ▁known ▁vit am ins , ▁a ▁large ▁brown ▁" c andy " ▁made ▁of ▁li ver ▁extract ▁flav ored ▁with ▁pe pp erm int ▁oil ▁( to ▁supply ▁any ▁unknown ▁vit am ins ), ▁and ▁mi xt ures ▁of ▁highly ▁pur ified ▁individual ▁am ino ▁ac ids . ▁The ▁main ▁outcome ▁measure ▁was ▁nit ro gen ▁balance . ▁Rose ▁noted ▁that ▁the ▁sympt oms ▁of ▁nerv ous ness , ▁exhaust ion , ▁and ▁d izz iness ▁were ▁encountered ▁to ▁a ▁greater ▁or ▁less er ▁extent ▁whenever ▁human ▁subjects ▁were ▁dep riv ed ▁of ▁an ▁essential ▁am ino ▁acid . ▁ ▁Ess ential ▁am ino ▁acid ▁def ic iency ▁should ▁be ▁distinguished ▁from ▁protein - energy ▁mal nut r ition , ▁which ▁can ▁manifest ▁as ▁mar as