"Quanta frutta mangia l'uomo?"
Not really. That is an somewhat awkward translation. It is common to hear either How much fruit does the man eat? or How many kinds of fruit does the man eat? The meanings are different, of course. If you knew what specific kind of fruit he was eating, you might hear How many apples (or oranges, etc.) does he eat?, but not How many fruits does he eat?
Fruit is an uncountable noun, therefore has no plural and you should use "How much" instead of "How many". There is a plural form of fruit, but it changes the meaning to "type of fruit", as in the question "Which fruits do you like?"
Reference (part of it in Spanish): http://www.wordreference.com/es/translation.asp?tranword=fruit