When William Shakespeare wrote this line in Act 1 Scene 2 of Julius Caesar it appeared to be a warning to Caesar of his impending surprise surgery in Act 3. In reality was Shakespeare’s way of issuing a Public Service Announcement to the masses; radio and television were still a few years away. March 15th is Lupercalia, an ancient Roman religious holiday. But like many of the Jewish dietary laws, the reason for this warning was based on health and not religious doctrine.
Although they appear to be sweet and juicy in March, Ides do not fully ripen until May and if eaten early contain amygdalin, a cyanogenic glycoside composed of cyanide and sugar also found in apple, pear and cherry seeds. When metabolized in the digestive system, this chemical degrades into highly poisonous hydrogen cyanide (HCN) and can prove fatal.
So please beware and do not consume Ides in March, but feel free to enjoy this tasty treat in May and throughout the summer!