Oops, my mistake.

When I made my first stew (a poison one) yesterday, I lost 24 food points. After reading your response, I just experimented and made a non-poisonous one, and (yay!) I gained 22 food points.

Note to self: poison, bad! non-poison, good!

***********************
(If I were more motivated, I would attempt each of the possible recipes several times, and keep track of the food points.)