If you must eat plants and can't watch the animals then:
Spread a bit on your skin, wait a while to see if there's a rash. Touch some to your lips and tongue, again waiting a while to see if there's a reaction. Eat a tiny bit, wait a while. Eat a larger bit and then wait. Continue upping the dose.
This is from memory from the SAS survival guide. Should take days and isn't very safe but may be the best you've got.
Spread a bit on your skin, wait a while to see if there's a rash. Touch some to your lips and tongue, again waiting a while to see if there's a reaction. Eat a tiny bit, wait a while. Eat a larger bit and then wait. Continue upping the dose.
This is from memory from the SAS survival guide. Should take days and isn't very safe but may be the best you've got.