Gee H, surely we can at least say it won't hurt to take C. Some candida yeasts do try to live on our throats, if we take vitamin c in powder dissolved in water, it will at least kill the yeast in our throats.
If we all waited until someone spends the millions of dollars to invent a special microscope to put into the guts of hundreds of people to see what actually happens to vitamin c down low in the gut, we'll be waiting long past our lifetimes.