Hi Lucy, If you check under Holistic Veterinarians in Google search for
your area, talk to a vet about human food additives for cats.
Here's one link : http://www.shirleys-wellness-cafe.com/vetlist.htm
I do know that my cat when she was younger loved green peas like they
were candy and green beans some, but the fresh/frozen green peas she
still loves.  For a treat now, I give her Temptations - she loves
Chicken or Turkey flavored.  But when we are out, I save the bag and
put cheap cat food in it and do a big Treat TODO over them and she
loves it just the same.  Treats you have to be careful of caloric
weight gain.  Man, the cat can pack on the fat if you are too loose
with the packaged treats or with smorgasborg of all you can eat rich
cat foods all the time.  We learned to take our cat's food up at night
- protects from night crawling bugs - spills if we have to get up and
might bump it by accident - or from being gobbled up from a bored cat
with nothing to do all night but to listen for crickets outside and eat
catfood and stand "guard"!!  Personally, I say catfood.  If she is sick
and starts after my artificial plants, we get grass from outside.....is
that ok for a sick tummy or hair balls?  It worked for her,  Any way
that's my story and that's more than enough. Sorry to be so long.
Bttngl

I've got a cat who is crazy about eating corn off the cob--I hold the cob
and he'll bite off kernels.  He'd go after the cob, too, if I let him.
Several of my cats will nibble on cooked broccoli and peas.  They don't seem
to go after fruit as much.  Avoid onions and I believe garlic--they cause
severe disease in cats and dogs.

Bonnie