I agree with Nai,
I sat and ate 1/2 watermelon to myself with DD1( summer PG) its the most refreshing thing ever
Frozen bananas are yummo too and it keeps the kids happy
I would imagine you would have to eat KILOS of certain fruits and veg for it to be a problem and I cant see anyone being able to eat such quantites, PG or not.
Sounds like a myth to me.