Excerpts from Vitamin C and the Common Cold by Linus Pauling

"The mechanism of its [vitamin C] effectiveness against viral infection, such as a common cold, is not yet known. I have, however, formulated the hypothesis (which has not yet been tested by experiment) that the effectiveness of ascorbic acid in providing protection against viral diseases results from its function in the synthesis and activity of interferon in preventing the entry of virus particles into the cells. The discovery of interferon was reported in 1957 by Isaacs and Lindenmann. It is a protein that is produced by cells infected by a virus and that has the property of spreading to neighboring cells and changing them in such a way as to enable them to resist infection. In this way the interferon ameliorates the disease." (p. 38)

"First, for good health I recommend the regular ingestion of an adequate amount of ascorbic acid. I estimate that for many people 1 g [gram] to 2 g per day (1000 mg to 2000 mg per day) is approximately the optimum rate of ingestion. There is evidence that some people remain in very good health, including freedom from the common cold, year after year, through the ingestion of only 250 mg of ascorbic acid per day. The requirements of a few people for ascorbic acid may be expected to be even smaller. For some people optimum heath may require large amounts, up to 5 g per day or more." (p. 84)