**6. Oral vs. intravenous Vitamin C**

The pharmacokinetic studies of Levine and Padayatty [28, 29], on Vitamin C, indicate that after oral administration of 200 mg of the nutrient, the maximum plasma concentrations obtained, are not superior to 70–80 μM. This is due to a "tight control," operated by several different mechanisms, including, among others: bioavailability, intestinal absorption, tissue accumulation, renal reabsorption and excretion, and utilization rate as a function of homeostasis. On the contrary, when Vitamin C is administered intravenously, "tight control" is bypassed, until renal excretion restores equilibrium, depending on the dose administered [51].

Therefore, according to these data, the intravenous administration of Vitamin C is the only way to achieve plasma concentrations in the order of millimoles, necessary to kill cancer cells.

However, this view is in disagreement with the following evidences:

