Either all at once, or over a lifetime?
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Cinnamon can cause permanent damage in high doses.
Other than that and the others mentioned here, probably just old, rotting ones would be bad.
How high?
It appears to be 0.1mg/kg of body weight too avoid coumarin overdose (which is much stronger in Cassia than ceylon cinnamon), which is toxic to the liver: https://ovidsp.dc2.ovid.com/ovid-new-a/ovidweb.cgi?T=JS&PAGE=fulltext&D=ovft&AN=01445481-201002000-00007&NEWS=N&CSC=Y&CHANNEL=PubMed
