Hi, Athene.
I just want to mention that vitamin C is part of the antioxidant network, as defined by Prof. Lester Packer in his book "The Antioxidant Miracle" (a hokey title, but a good book). The network consists of glutathione, vitamins C and E, alpha lipoic acid, and coenzyme Q10. The defining feature of this network is that these antioxidants regenerate each other via certain relationships when they become oxidized. In particular, vitamin C is normally recycled by glutathione. Glutathione is usually found to be depleted in ME/CFS. If vitamin C is supplemented under this condition, the ratio of reduced to oxidized glutathione will be lowered even further. Vitamin C can pick up some of the load of oxidative stress from glutathione, and thus give some benefit, but it can't do all the many jobs that glutathione normally does. So I think it is better to raise glutathione by lifting the partial methylation cycle block than to try to substitute it with vitamin C.
The late Dr. Robert Cathcart found that if vitamin C is taken at dosages up to bowel tolerance every day (which he did himself for many years, because it was the only thing that he found would work for him) the relationship between glutathione and vitamin C in the antioxidant network can be reversed. That is, vitamin C will regenerate glutathione.
But at dosages short of those near bowel tolerance, taking vitamin C in the presence of glutathione depletion probably worsens this situation. Oxidative stress may be lowered this way, but the buildup of toxins, the immune dysfunction, the methylation deficit, the lack of folates to make new DNA and RNA, etc., will likely not be corrected.
Best regards,
Rich