I am a supporter of the Linus Pauling Institute at Oregon on State University. In their most recent research newsletter for the fall-winter 2018 publication, they summarize the most Frequently Asked Questions about Vitamin C.
Q: What brand of vitamin C should I take?
A: Expensive vitamin C supplements have no advantage over generic vitamin C. USP or NSF certified preparations pass their quality bar.
Q: Should I take buffered vitamin C?
A: Buffered vitamin C will reduce stomach upset if you are prone to it. Buffered preparations contain calcium, magnesium, or sodium salts. However, a high dosage of buffered vitamin C can result in electrolyte disturbances and sometimes kidney stones.
Q: What about liposomal vitamin C?
A: There are no controlled studies demonstrating the superiority of this form of vitamin C.
Q: Is there a difference between synthetic and natural vitamin C?
A: No.
Q: Is there any advantage to taking vitamin C combined with other flavonoids such as rosehips?
A: No
Q: Is intravenous vitamin C beneficial?
A: It may be beneficial in sepsis as part of some cancer regimens. By itself, it is not a treatment for cancer or heart disease. 40 years of experimentation with vitamin C, either alone or in combination with lysine or proline have not demonstrated any benefit.
Q: Can large amounts of vitamin C cause harmful effects?
A: Very high doses of oral vitamin C cause gastrointestinal upset. Also, vitamin C is metabolized to oxalate, and may increase the formation of kidney stones.
The bottom line: Plain vitamin C — synthetic or from foods — is a valuable micronutrient. Should you have further questions about vitamin C, I direct you to the Linus Pauling Institute Micronutrient Information Center. Their vitamin C page is updated on a regular basis and is the best source of information I know.
Visit it here:
https://lpi.oregonstate.edu/mic/vitamins/vitamin-C