There have been a ton of studies that say the exact opposite. Many in other countries that are not influence by big pharma. I think I trust them a lot more than this one.
I conducted my own study the subject was my sister middle-age with a heart condition extremely sick for 10 days probably the flu I finally convince her to take high-dose vitamin C vitamin D three and zinc and quercertin. within two days she was back to normal I deem this a successful study.
By the way high dose is 10,000 mg three times a day using liposomal vitamin C not the regular vitamin C