According to one self-proclaimed authority, vitamin C therapy is nothing but health quackery. [Quackwatch.com] WebMD advises physicians that supplemental vitamin C is only marginally able to reduce symptoms and duration of the common cold. But the primary study referred to employed just 200 milligrams of vitamin C, barely enough to marginally raise blood levels of this essential vitamin. [WebMD June 20, 2012]
None of this negative science discouraged laboratory researchers in China however. They inoculated mice with influenza virus and then injected 3 milligrams of vitamin C per gram of body weight. (Laboratory rats weigh about 300-500 grams.) [University of Wisconsin] So these animals were injected with 900-1500 mg vitamin C.
A 70-kilogram (154-lb) human weighs in at 70,000 grams. So the amount of vitamin C the lab rats received was equivalent to 21,000 mg in a human weighing 154-lb (70 kilogram). That is a lot of vitamin C. Far lower doses of vitamin C can be used in humans to achieve maximal blood concentrations.
So what happened to the intentionally sickened mice? Well, the viral levels in their blood were 10-100 fold lower than untreated mice. The vitamin C-treated mice exhibited very little lung inflammation, which in turn lowered their death rate. [Chinese journal of tuberculosis and respiratory diseases May 2014]
So how does this animal lab research translate to humans? Carol Johnston, a long-time vitamin C researcher at Arizona State University took a small group of seemingly healthy non-smoking men (tobacco reduces vitamin C blood levels) whose vitamin C blood levels ranged from adequate to low and gave them 1000 mg of vitamin C/day for 8 weeks. Over that time 11 of the men who took an inactive placebo tablet and 7 men who took vitamin C develop cold symptoms, a 45% difference. Duration of cold symptoms declined -3.2 days in the vitamin C-treated group. Another bonus: the males in the vitamin C-treated group were more physically active (+39.6%).