Food protein amyloid-like nanofibrils are gaining interest as new food ingredients. Nanofibrils can self-propagate by seeding and can cross-seed the fibrillation of similar proteins from other species. Nanofibrils can potentially survive digestion and spread to other parts of the body. Currently, there is limited knowledge on the propensity for food protein nanofibrils to cross-seed fibril formation of similar human proteins. Thus, it is prudent to examine their impact on human health before employing nanofibrils in food. This study used lysozyme as a model to examine the seeding and cross-seeding reactions between two unique fibril polymorphs (formed at pH 2, and pH 6.3) of lysozymes from human and hen. Both polymorphs of HEWL could cross-seed aggregation of HLZ, but this reaction was markedly reduced under simulated gastric conditions. Surprisingly, the 6.3 fibril polymorph was dominant even at pH 2, indicating, distinct polymorphs of the same protein have unique abilities to self-propagate.