The vitamin C trials that failed in the 1980s and the intravenous ascorbate research being conducted today are not testing the same thing, and the reason comes down to a ceiling the human body imposes on how much vitamin C can enter the blood by mouth.
That ceiling is well characterized in the federal nutrition literature. Eating five to nine servings of fruits and vegetables daily produces steady-state plasma vitamin C concentrations of 80 micromoles per liter or less. Pharmacokinetic modeling published in Annals of Internal Medicine predicted that even the maximum tolerated oral regimen, 3 grams every four hours, would push peak plasma concentrations only to about 220 micromoles per liter. The same modeling predicted 13,400 micromoles per liter for a single 50-gram intravenous dose.
