Maybe. Studies show zinc can shorten the duration of a cold by about one-third. Taking high doses of vitamin C may also reduce the length of a cold. Research shows between 1,000 and 2,000 mg of vitamin C daily reduced the duration of a cold by about 14% in adults. It can also make symptoms less severe.  Echinacea, black elderberry syrup, beetroot juice, and probiotic drinks may also help reduce the cold's length and severity, but more research is needed to confirm the effects.