I'm not that experienced with LSD, haven't been able to score it since I was a kid...40 years ago, but the "vitamin C tripping" myth? was around even then and I heard that it'll make you trip harder and I also heard you can kill a bad trip w/it...so it sounds like the placebo effect is in effect...IDK.
That said, DMT trips, especially Ayahuasca, can definitely be potentiated by eating ...well, pretty much anything IME.
Fruit is especially good for this though...mind you, this is IME. It is not based on any real research, just anecdotal evidence, but it seems to work well with tryptamines for me.
Oh, I also think it's probably more the fructose than the vitamins...you know, energy and all that.