Effects of Psilocybin: a loss of appetite, coldness in the extremities, increase of heart rate, numbness of the mouth and adjacent features, nausea, elevated blood pressure, weakness in the limbs (making locomotion difficult), muscle relaxation, yawning, swollen features and pupil dilation.
Hmm a lot of those sure sound like the symptoms associated with food poisoning...
http://en.wikipedia.org/wiki/Foodborne_illness#Symptoms_and_mortality
Symptoms [of food poisoning] typically begin several hours to several days after consumption and depending on the agent involved, can include one or more of the following: nausea, abdominal pain, vomiting, diarrhea, gastroenteritis, fever, headache or fatigue.
If by a lot you mean one (nausea), then yes. I get nauseous on roller coasters too, does that mean they cause food poisoning?
Effects of Psilocybin are also evident within thirty minutes of consumption, not "several hours to several days."