לא ניתנה תורה אלא לאוכלי המן – The Torah was not given – except to those that ate the manna
Many years ago I read a book by a nuclear physicist (if I remember correctly I think his name was Cyril Domb, he was a ba'al teshuva who died young R"L) and in one chapter he propounded an idea that kedusha which transcends this world, should be realized as traveling faster than the speed of light, for as object approach the speed of light they get larger and larger, so he figured that if they can beat the speed of light, they can transcend the space of matter, and this is the concept of the Holy Ark in the Holy of Holies that did not take up any space (See Rabbi Nachman's stories of Ancient Times, of the Seven Beggars, the 4th day, the Hunchback Beggar, there Rabbainu revealed that to get to the tree which stands out of space, one needs to acquire it's attributes, the body (trunk) of the tree is truth (this is in fact light, as the verse says, שלח אורך ואמיתך), and its roots are humility, fear of Heaven, and faith).
[This works nicely with an analogy my friend (S.R) always gives to explain why tzaddikim have extra critical judgement by HY, as it says הקב"ה מדקדק אתם כחוט השערה, וסביבם נשערה מאד. So he says it's like a car, as long as the car is just inching along one can turn the steering wheel, and even jerk it which ever way he wants, but when a car is going 200 miles an hour, a little touch on the wheel can send it flying. Kedusha is like faster than the speed of light, so any nuance there makes a world of difference.]
So I was thinking along these lines, to explain why to really receive the Torah one has to get his nourishment only from the manna. Because any food that leaves waste in the body, if the body is on the level of holiness of the Torah, it is like going super fast, and even the smallest iota of waste would be utterly huge to infinity.
Na Nach Nachma Nachman MeUman