As the weather gets colder, jackets and coats are replacing sweaters, winter hats are replacing baseball caps, and it may be a good idea to invest in Kleenex, as it seems that it is cold season.  When thinking of a remedy for the common cold, sleep, chicken soup and vitamin C may come to mind.  While no one will argue the power of a good night’s sleep and some homemade chicken soup, researchers are wondering how effective vitamin C is in warding off the common cold.  As colds are the number one reasons for doctor visits, as well as number one reason for absence from work or school, it may be worthwhile to delve deeper into this question.

The idea that large doses of vitamin C may reduce symptoms of the cold was first made famous by Linus Pauling in the 1970s.    Pauling’s research was on a group of school children in a skiing camp in the Swiss Alps. The children who took 1 gram of vitamin C a day had a significant decrease in incidence and duration of colds as compared to the children who did not take vitamin C.  It was, however, argued that a group of school children was not a good representation of the general population and that a lot more research needed to be done.

In the past 40 years since this original research came out, numerous epidemiological and placebo controlled  studies have been done looking at the efficacy of using mega doses of vitamin C to prevent and treat the common cold. Dozens of  studies have been conducted with individuals taking multiple grams of vitamin C a day, and the majority of the research has shown that large doses of vitamin C does not prevent or help cure the common cold. However, interestingly, the results indicate that athletes may benefit from supplementation of vitamin C.

A recent review article, published in 2009 in the Journal of the American Association of Nurse Practitioners, found that taking vitamin C may decrease the length of the cold but does not seem to affect the severity of the symptoms or act as a prophylaxis. A similar conclusion was found in the most recent meta-analysis on this topic, published this past January in Cochrane Database of Systemic Reviews. Seventy-two studies were analyzed, and the researchers found that vitamin C may decrease the length of the cold and the severity of the symptoms, but does not act as a prophylaxis except in individuals, such as marathon runners, involved in extreme physical activity

It is interesting to note that based on the above findings, researchers have recommended that given that vitamin C may shorten the duration and severity of the cold, it is worthwhile to try taking the supplement and seeing if it works for you.

However, is this safe?  The recommended daily allowance of vitamin C is 75 mg/day for women and 90 mg/day for men.  Because the kidneys can efficiently excrete excess vitamin C, no adverse effects were found even when taken in doses higher than 2,000 mg/day (the recommended upper limit of the vitamin.)

However, some find that large doses of the supplement may cause diarrhea and nausea.  It is also thought that though mega doses of vitamin C do not cause kidney stone formation in individuals with no history of kidney stones, it can be an issue for those with a history of kidney stones; they should not take more than 100 mg/day of this vitamin.  Vitamin C also has several drug interactions including increasing iron absorption, increasing the activity of anti-coagulants and potentially reducing the efficacy of certain chemotherapeutic drugs. Therefore, it is always important to talk to your doctor before taking mega doses of vitamin C.

All in all, it appears that mega doses of vitamin C may help reduce the duration of the common cold and is relatively safe and cheap, but it still doesn’t taste as good as chicken soup.

by Shoshana Genack