Maximal Ascorbate Cmax in Humans with Oral Dosing and Its Efficacy Threshold:

Taking 3 grams/4 hours can achieve 220uM Vitamin C in blood.

What type of cancer might respond to this oral dosing?  Lymphoma.

Proc Natl Acad Sci U S A. 2008 August 12; 105(32): 11105–11109.

What needs to be clarified is what direct cytotoxic effect additional ascorbate has and what immune cell augmenting effects that ascorbate has as an immune system side therapy.  The direct cytotoxic effect is one important mechanism, but it could not be the only one in the immunosurveillance against aberrant cells that happens routinely before solid tumor carcinogenesis.  It must be remembered that cells accumulate ascorbate against a gradient, often to 100 times higher concentration than what is in the serum environment.  1mM-4mM concentrations in lymphocytes is an unremarkable baseline concentration.  Given the stoichiometric depletion of ascorbate in an active immune response, it is not surprising that bowel tolerence in humans increases greatly in times of immune system challenge by any of the assorted antigens that it would face in fungal, bacterial, or viral infection as ascorbate is literally burned up like fuel.

Dynamic immune system cells operate in very extreme environments and burn through a lot of ascorbate.

Ascorbate burn rate by macrophages

Well known ascorbate burn by IL- therapy activating immune "killer cells" resulting in severe vitamin C depletion.

Neutrophils, our first line defense microbe eaters, use oxidative burst and may soak up an additional 8,000 umoles/L in times of attack.

So then, flux of reduced ascorbate through the physiology much like the running of water through a washing vessel of fixed volume may be more important than Cmax.  If the same dose of oxidized ascorbate remained stagnant through the vessel of the same size as a vessel through which reduced ascorbate were constantly running through, there would be less redox activity and more redox activity, respectively.  So the focus upon Cmax without examining immune cell function may be misguided especially in terms of daily immunosurveillance and prevention of cancer or immune system remission and/or mitochondrial reversion of early cancer.

The field of Vitamin C science has been partially demystified in the last 3 decades, but there is still much to be elucidated.