Supplementing at least 2 grams of vitamin C per day during a cold was more beneficial than 1 gram per day.

“a comparison of 12 trials found a 13.5 percent reduction in cold duration among children compared to an 8 percent reduction in adults”

“a meta-analysis of 23 clinical studies involving more than six thousand participants sifted through these different factors and found that supplementation of at least two grams per day of vitamin C during a cold had a greater benefit compared to a dose of one gram per day”