Non-protein amino acids like azetidine and canavanine can accumulate in human proteins and potentially cause misfolding.

“this idea that these non-protein amino acids could accumulate in our proteins and cause misfolding because this trna puts in a wrong amino acid not one of the 21 that we actually use something like there's one called aze which is in sugar beets and there's another one called cannavane and alfalfa sprouts and if you get too many alfalfa sprouts there's pretty good documentation in the medical literature of this lupus-like autoimmune syndrome”