Forthepastfewdecades,therehavebeenchangesinpeople'sdiet.Thefoodfromplants,traditionallydominatingtheirdietsuchasgrains,fruitsandvegetables,isholdingagrowinglysmallpercentagenow,whiletheprotein-containingfoodfromanimalssuchasmilkandmeathasremarkablegrowthinproportioningeneral.Thepossiblereasonsresultinginthechangescanbeasfollows:First,therehasbeenanincreaseinpeople'sincomeandsupplyofhigh-qualityfood.Second,people'sdietstructureisbecomingmorescientific.