Womenswisdom, I used to believe, like you, that vitamins, especially in megadoses, were not necessary bc they did not occur in nature. I actually thought they were dangerous. I was exposed to the scholarship of Abram Hoffer, and as I mentioned further on, Linus Pauling, recipient of two, unshared Nobel prizes. Both postulated the revolutionary idea that humans are evolving in response to their nutritional and environmental surroundings (toxins and so forth).
In our family, we juice, make green smoothies, and prepare foods using traditional methods and ingredients.
There is a wonderfully illustrative discussion of vitamin C in evolutionary biology in Steve Hickey's excellent book: Vitamin C, the Remarkable and Contraversial Healing Factor. Many mammals have stopped producing their own vitamin C, over time. Humans are one such animal, and perhaps it is bc we have had vitamin c in abundance in our environment. In any case, I invite anyone interested to explore further.
The studies you cited used 1,000 mg of vitamin C. Almost no one would take issue with a dosage available in an ordinary packet of Emergen-C. Personally, I feel great about taking megadoses of nutrients while pregnant. A mere 1,000 mg stresses me out, as a minute dose! LOL.
I've mentioned on other threads discussing vitamins that I became interested in this area of research when all three of my children (one under one year at the time) became gravely ill with whooping cough. Because Vitamin C is antibacterial, and antiviral in gram level doses, I treated my children with 25-30 grams of vitamin C. (Divided doses, of course). They were well in days.
Great terms to google are cancer and vitamin c, megavitamin therapy, Klenner and vitamin C.