The largest US peptide manufacturers are Contract Development and Manufacturing Organizations (CDMOs) such as Bachem, AmbioPharm, CordenPharma, and PolyPeptide Group, which produce peptide APIs (Active Pharmaceutical Ingredients) at pharmaceutical scale
A review of the research literature has failed to show any serious side effects, although there have been reports of gastric cramping nausea, abdominal bloating and allergic reactions
(PubMed) Powers HJ, Hill MH, Mushtaq S, Dainty JR, Majsak-Newman G, Williams EA
: in vitro, in vivo , BPC-157 ( ) ,
Among the most discussed peptides today are Sermorelin, Tesamorelin, and Ipamorelin
Regarding the effects as you mentioned, digestion etc I didn't feel anything special around those