For a few years I have been using megadoses of ascorbate taken until bowel intolerance [at about 2 grams per 2 hours] for treating viral infections. My daughter, when ill, experiences bowel intolerance at about 1 gram every 2 hours. I should point out that my recent illness was not just seasonal influenza. It started with cough, headaches, joint aches and fever. After that the illness became more severe including diarrhea, chicken pox-like rash, blood discharges from my nose and fluid retention in the scrotum with severely swollen testicles. Doctors were baffled.
Medical studies indicate that the absorption of orally ingested ascorbate by the body is not proportional to the amount ingested. “New insights into the physiology and pharmacology of vitamin C” - Sebastian J. Padayatty and Mark Levine
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC80729/"When taken orally, ascorbic acid is well absorbed at lower doses, but absorption decreases as the dose increases." This was determined by measuring ascorbate in blood plasma and urine. The surplus ascorbate is excreted in the urine. Thus a plateau effect [for absorption] starts occuring at around 1.5 grams ascorbic acid ingested. The research indicates little additional benefit of megadoses beyond about 3 grams [taken orally] and confirmed my experience that I experienced bowel intolerance at 2.5 grams consumed every 2 hours. I was consuming about 24 grams per day and urinating every 2 hours. I can’t see how any additional consumption beyond bowel intolerance levels [24 grams per day] could be more beneficial. "Only when ascorbic acid is administered intravenously, the limiting absorptive mechanism is bypassed and very high plasma levels are attained."
Comment about taking calcium ascorbate:- My understanding of the literature is that ascorbate is the effective agent. According to Jane Higdon, R.N., Ph.D. of the Linus Pauling Institute – “Mineral salts of ascorbic acid (mineral ascorbates) are buffered and therefore less acidic. Thus, mineral ascorbates are often recommended to people who experience gastrointestinal problems (abdominal pain or diarrhea) with plain ascorbic acid. [In my case I was suffering from diarrhea]
There appears to be little scientific research to support or refute the claim that mineral ascorbates are less irritating to the gastrointestinal tract. When mineral salts of ascorbic acid are taken, both the ascorbic acid and the mineral appear to be well-absorbed.”
Quoted from “The Bioavailability of Different Forms of Vitamin C”
http://lpi.oregonstate.edu/ss01/bioavailability.html